Gravity Study of the Crust beneath the Babouri-Figuil and Mayo Oulo-Léré Sedimentary Basins, North Cameroon and South Chad

Gravity Study of the Crust beneath the Babouri-Figuil and Mayo Oulo-Léré Sedimentary Basins, North Cameroon and South Chad | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Gravity Study of the Crust beneath the Babouri-Figuil and Mayo Oulo-Léré Sedimentary Basins, North Cameroon and South Chad Bouba Saidou, Apollinaire Bouba, Valentin Oyoa, Loudi Yap, Joseph Kamguia, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-1664918/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract In this work, the crustal structure study of Babouri-Figuil and Mayo Oulo-Léré sedimentary basins was carried out through the interpretation of gravity data. These data were obtained by combining to the terrestrial gravity data those obtained from EGM2008 model. The Analysis of the terrestrial Bouguer anomaly maps revealed negative and positive anomalies. Negative anomalies would be the signature of sedimentary basins while positive anomalies would be attributed to basaltic rocks under granitic environment. To isolate anomalies due to deep structures from those due to near surface structures, we used the empirical method. This method testifies that the residual map of order 4 is an appropriate one. In order to conduct the quantitative interpretation of the combined gravity data, six profiles were drawn on the residual Bouguer anomaly map and therefore were interpreted using spectral analysis and 2.5D modeling methods. The results indicate that the mean depths of mass sources near surface of Babouri-Figuil and Mayo Oulo-Léré sedimentary basins were 1.50km and 1.55km respectively. Moreover, Babouri-Figuil is constituted of two formations of different density contrast while Mayo Oulo-Léré shows three formations. These models helped us to clarify the geological structure of the study area. The results of the present study allow greater understanding the sedimentary basin thickness. EGM2008 model Bouguer anomaly Sedimentary basins Residual anomaly Empirical method Spectral analysis 2.5D modeling Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 1. Introduction The study area located between longitudes 13° to 14°30E and latitudes 9° to 10°30N is presented in Fig. 1 . It covers the Babouri-Figuil and Mayo Oulo-Léré sedimentary basins. The main studies carried out in these basins have mainly focused on geological studies. These include the works of (Allix et al. 2000; Allix and Popoff 1983; Dejax et al. 1989 ; Ndjeng et al. 1988 ; Ndjeng 1992 ; Colin et al. 1992 ; Ndjeng 1994 ; Brunet et al. 1988 ; Bessong 2012 ; Ntsama 2013). These works have shown that the Babouri-Figuil and Mayo Oulo-Léré sedimentary basins are two small Wealdian basins filled with continental sediments. These sediments are mostly detritics and made up of an alternation of fine sandstones, silts and indurated marls. However, from geophysical point of view in general and gravimetry in particular, the thickness of these basins is still poorly understood. The gravity data available in this area are obtained by ORSTOM (Office de Recherche Scientifique et Technique d’Outre Mer) during the various reconnaissance campaigns. The itineraries followed tracks, carrossables roads and sometimes water courses. Despite these efforts, these data are very sparse and present many gaps. A Bouguer anomaly map realized with such gaps presents many insufficiencies. Its interpretation leads to erroneous conclusions. To solve this problem, it would be appropriate to densify data by carrying out a new gravity campaign. Unfortunately, gravity campaigns are very expensive. An elegant solution to this problem consists to densify the measured gravity data by using the EGM2008 field model and making them usable (Bouba et al. 2017 ). These data have been reduced by using a series of corrections to eliminate the non-geological causes of gravity variations. The obtained database allowed to establish a new gravity map of the region. In this paper, we applied spectral analysis and 2D.5 modeling methods to the combined gravity data in order to determine the depth and density contrast of the crustal structure beneath the Babouri-Figuil and Mayo Oulo-Léré sedimentary basins. These methods have been used to isolate causative bodies by representing them as polygonal bodies in two dimensions (Toushmalani and Saibi 2015 ). Similar approaches were used successfully to improve the subsurface structure geometry of Algeria (Farhi et al. 2016 ; Saibi et al. 2006 ) mentioned the relationship between the observed gravity anomalies and the obtained models of the integrated 2D gravity interpretation technique. 2. Geological Setting Cameroon has two types of sedimentary basins: coastal sedimentary basins located in the southwest of Cameroon and intracontinental sedimentary basins located in the northern part of the country. Many of these latter are connected to the Yola branch belonging to the Benue ditch. These are Koum, Hamakoussoum, Babouri-Figuil and Mayo Oulo-Léré basins. The Babouri-Figuil sedimentary basin and that of Mayo Oulo-Léré are small basins elongated of EW direction. They are located respectively between latitudes 9°44'-9°50' and 9°39'-9°44' and longitudes 13°44'-14°02' and 13°43'-14°28' (Fig. 2 ). These two basins have Wealdian facies equivalent to the Bima formations in Nigeria (Ntsama 2013). The Babouri-Figuil sedimentary basin is the most northern of the small Cretaceous basins with continental sediment in north Cameroon. It is lengthened on nearly 45km with a width ranging from 1km towards Figuil and 8km between the villages of Babouri and Sorawel (Ndjeng et al. 1988 ; Ntsama 2013). It is a basin dotted with mounds and basic sandstone. Its sedimentary pile locally reaches 1500m (Danra Moh Guela et al. 2019 ). These sediments are constituted of fine sandstones, silts and marls. Their presence testifies the sedimentation whose origin would be linked to the indicator of many emersion phases (Ndjeng 1992 ). The abundance of flore and the existence of evaporation levels are present throughout the basin. The swamp environment under hot and humid climate is revealed by the abundance of Estheries whose eggs dissemination is favored by drying seasonal periods (Brunet et al. 1988 ). The presence of leaves and footsteps of dinosaurs have been found in Mayo-Tafal (Dejax et al. 1989 ). The Mayo Oulo-Léré basin is over 50km long and less than 10km wide. It extends towards the south of Chad in the Léré area. It is separated from the Babouri-Figuil basin by granite complexes culminating at 800m of altitude. It consists mainly of silts and hardened clays. Basaltic rocks present in the sediments in form of sills set up a metamorphism of contact (Ndjeng 1994 ). Through on Paleoflore study, the Mayo Oulo-Léré sedimentary basin is constituted with invisible small grabens (Ntsama 2013; Guiraud and Maurin 1991 ). These grabens established in north-south extensive context are constituted with basaltic formations (Ndjeng 1992 ). Microfossils collected from this basin provides from anteaptian sedimentation. 3. Data And Methods 3.1. Gravity Data The gravity data used in this work provide from two independent sources. One is derived from measured gravity data and the other is obtained from Earth Gravity Model EGM2008. 3.1.1. Terrestrial Gravity Data The terrestrial gravity data used in this work were collected between 1960 and 1968 by the Office de Recherche Scientifique et Technique d'Outre-mer (ORSTOM) during various reconnaissance campaigns. These data were obtained between latitudes 9°00' and 10°30'N and longitudes 13°00' and 14°30'E. The acquisition campaigns of these data were obtained by a car, along the roads, carossable tracks and sometimes water courses. The measurements were taken every 3km. Several gravimeters (Worden and Lacoste & Romberg) were used to measure the variations of gravity. The calibration of the gravimeters was carried out on stations of the Martin network which are defined in Potsdam system. The precision on the gravity values is the order of 0.2mGal. The location of the measuring stations was determined on topographic maps by compass tracking. The average error in the position of the stations is estimated at around 200m. Altitudes were estimated using barometers and altimeters (Wallace and Thierman, Thommen). The accuracy on the values of altitude depends on the climate, the difference of altitude between the reference station, the measure point and the distance from the stations. The error on altitude of the stations can reach 10m when the weather conditions are unfavorable and 3m otherwise. The terrestrial Bouguer anomaly map presented in Fig. 3 is plotted using the Generic Mapping Tools (Wessel and Smith 1995 ). This map shows two main zones of anomalies: low and high zones. Low anomalies zones are divided into two parts. The first part located in the northern part of the study area covers the towns of Hamakoussou, Dembo, Dourbey, Guider and the entire sedimentary basin of Babouri-Figuil. In this sector, low anomalies are unevenly distributed (-65 to -35mGal). This situation would be due to the lack of terrestrial gravity data in the sector. The second part located in south of Léré is also constituted of low anomalies with a minimum that can reach − 60mGal. These anomalies would be due to the filling effect of the Pala-Lamé sedimentary basin in Chad. High anomalies zone covers the southwest of Garoua, Lagdo and Bibémi towns and the entire area of Mayo Oulo-Léré basin. The amplitude of these anomalies is around − 25mGal with a maximum at 0mGal in the northern part of Bibémi and Mayo Oulo-Léré sector. These anomalies would be due either to the upwelling of magmatic fluids through the lithospheric fractures in the sedimentary zone or to denser rocks found on surface (Louis 1970 ). 3.1.2. Data from EGM2008 In this part, gravity data were obtained using the Earth Gravity Model. This model provides more informations on the Earth's gravity field for various geophysical applications (Palvis et al. 2008 ; Bonvalot et al. 2012 ). Its utilization is advantageous because it possesses: (1) harmonic coefficient up to degree and order 2190 (Weiyong and Rummel 2013 ). (2) Good spatial resolution and good ability to provide gravity data. (3) Spatial resolution of 5 arcminutes corresponding to a wavelength of 9km, approximately 6 times more resolution than other models. (4) Gravity data over the entire Earth, data obtained from disturbance analyzes of satellite trajectories and data from satellite altimetry over the oceans (Palvis et al. 2012 ). (5) Gravity data are freely obtained. (6) It provides more information on the areas devoid gravity data and geologically inaccessible. This model has been used in the localization of coal deposits in India, in the mapping of cratons and in the delineation of geological discontinuities in sedimentary basins (Jitendra and Pala 2015 ). According to (Bouba et al. 2017 ; Kamguia et al. 2007 ; Abate Essi et al. 2017 ) EGM2008 gravity data and terrestrial ones have the same precision; so they are stackable and can be superimposed. Data from this model are combined with terrestrial data in order to increase their density. Bouguer's correction is obtained by taking an average density of 2.67g/cm 3 . The densified gravity data thus obtained have permitted to establish a new Bouguer anomaly map by joining points having the same anomaly value (Fig. 4 ). For objectivity reasons, the Bouguer anomaly map is plotted by computer using the Generic Mapping Tools software (Wessel and Smith 1995 ). This map is interpreted in two gravity zones. The first zone located in the northern part of the study area, consists of a large low domain (-60mGal) visibly more developed than on terrestrial simple Bouguer anomaly map. It is in this area that Babouri-Figuil sedimentary basin is located. The Examination of this map shows that this basin tends to evoke the mark of sedimentary fill. We would imagine a lake basin where water courses brought their alluvium while the volcanoes spread their lavas. These anomalies may be due either to the collapse of sedimentary block or to the local thickening of sedimentary series generated by the depression of the basement roof. In south of Léré, we observe negative anomalie zone of -60mGal. These anomalies can be due to sediments deposits in this area. The second zone extends from Garoua town to Léré in Chad and up to Bibémi. This zone includes the Mayo Oulo-Léré sedimentary basin. It is characterized by high and positive anomalies. These anomalies could correspond to the intrusion of basaltic rocks under the sedimentary basin. However, the orientation of the isoanomal lines does not coincide perfectly with the basin direction. It suggests that, the intrusion would have been favored by tectonic process. The first and second domains are separated by strong gradient, which would result from discontinuities between crustal formations, such as faults, flexures or contacts of intrusive rocks. 3.2. Method 3.2.1. Regional/Residual separation In Benue sedimentary trough, the third-order of polynomial surface of regional anomaly has used (Kamguia et al. 2005 ). Such choice cannot be justified when we considered detailed interpretation of the basement. It is therefore necessary to define a criteria for choosing the regional surface which takes into account the variations of the gravity field in all directions. In this study we used the empirical method of (Zeng et al. 2007 ). This method permits us to determine a regional anomaly which presents the best resemblance to the prolonged Bouguer anomaly at optimum altitude. The degree of resemblance between two gravity fields g 1 and g 2 is determined by the correlation factor calculated by using the formula proposed by (Abdelrahman et al. 1989 ): where M and N are the number of sampling data along x -direction and y -direction respectively. Figure 5 a shows the curve giving the variation of the correlation factor as a function of continuation heights. It is an increasing curve which presented a maximum deflection noted C at a certain continuation heights. This deflection is given by the gap between the curve of the correlation factor and the line joining the two ends of the curve. In Fig. 5 b, we plot the curve giving the variation of the deflection C at each altitude as a function of continuation heights. This curve passes through a maximum altitude Hm = 25km called optimum altitude of upward continuation of the Bouguer and also corresponds to the depth of investigation in the region. For the choice of the regional degree, we calculated the coefficients of correlation between the upward continuation of the Bouguer map at 25km and the regional anomaly maps for different degrees (Fig. 5 c). We find that the upward continuation of the Bouguer map at optimal altitude present a maximum correlation with the regional anomaly map of order 4. Thus, residual anomaly map of degree 4 will essentially highlight the gravity effect of shallow structures in the study area. 3.2.2. Power Spectrum Analysis The Spectral analysis is a method that permits to define the planes of separation between several structures of different densities. When we plot the logarithm of gravity energy as function of frequency, the spectral curve has two slopes. The first slope located in the low frequencies corresponds to the deep structures. The second slope located in the high frequencies corresponds to the near surface structures. The average depths of gravity anomalies sources can be estimated from the relationship (Gerard and Griveau 1972; Dimitriadis et al. 1987 ): where is the variation of the logarithm of the energy spectrum; the interval of frequency. These depths permit to constrain the 2D1/2 modeling and assimilate the geological structures to the reality. The average error on each gravity profile is estimated at 5% of the obtained depth (Bouba et al. 2017 ; Nnangue et al. 2000 ). 3.2.2. 2D1/2 Modelling The Modeling consists to calculate the theoretical anomaly from simple shape of the structure of model and to compare it to observed anomaly. The best obtained model is that which corresponds to the structure whose calculated anomaly is assimilated to the observed anomaly by adjustment (Poudjom-Djomani 1993 ). In this part, 2D1/2 modeling is obtained by using Grav2DC software based to algorithm of (Cooper 2004 ; Talwani et al. 1959 ). This modeling was carried out by taking into account the depths calculated by spectral analysis, the geology of the region and the density contrast of the anomalies sources. The density contrast is calculated from the formula, C i = d 0 - d i where d 0 = 2.65g/cm 3 is the average density of the granites, d i is the average density of the ith formation (Noutchogwe et al. 2006 ). 4. Results 4.1. Presentation of New Residual Bouguer Anomaly map The residual anomaly map presented in Fig. 6 shows two anomaly sectors: positive sector and negative sector. The first sector is located in west of Garoua, northeast of the study area and east of Dourbey. The values of anomalies are between (0 to 15mGal). It would be due to the presence of heavy rocks in granitic environment. The analyze of this map also shows another positive sector which extend from Bibémi to Léré in Chad and include the Mayo Oulo-Lére sedimentary basin which is located inside positive anomaly zone (15 to 35mGal). These anomalies show that the Mayo Oulo-Léré basin does not have the morphology of sedimentary basin. It would correspond to a lake basin with a spectacular rise of heavy rocks probably basaltics. The second sector is constituted of negative anomalies. These anomalies are located in south of Garoua and around Dourbey where the Babouri-Figuil sedimentary basin is located. The values of these anomalies are between − 15 and − 5mGal. This could correspond to the sedimentary deposits of the Garoua trough in general and the Babouri-Figuil basin in particular. This basin constituted essentially of sandstone would be linked to the Benue trough. The Analysis of the map shows also another negative sector located in south of Léré on Cameroon-Chad border. In this sector the minimum value of anomalies is -25mgal. This would indicate the presence of weak formations compared to the surrounding formations. 4.2. Estimation of Mean Depth of Density Interfaces In this part, we used the spectral analysis to determine the depths of geological structures source of anomalies. Six profiles P1, P2, P3, P4, P5 and P6 have been traced on densified residual Bouguer anomaly map. P1, P2 and P3 were plotted on Babouri-Figuil sedimentary basin and P4, P5 and P6 on Mayo-Oulo-Léré sedimentary basin. All these profiles are executed perpendicularly to the main elongation of the structure to be studied. When we plot the energy spectrum logarithm as a function of frequency, the spectral curve presents two characteristic slopes. The first slope located in the low frequencies corresponds to the deep structures. The second slope which represents the high frequencies corresponds to the bodies near surface. In Babouri-Figuil sedimentary basin, two major discontinuities have been obtained by spectral analysis on profiles P1, P2 and P3 (Fig. 7 ). The first discontinuity corresponds to deep structures with depths estimated at 4.70km, 4.55km and 5.46km respectively for profiles P1, P2 and P3. These depths could correspond to the sediment-granite contact zone. The second discontinuity is associated with bodies near surface. The estimated depths are: 1.48km, 1.44km and 1.58km respectively for profiles P1, P2 and P3. The average value of depth in this basin is around 1.50km. This result agrees with those obtained by (Schowoerer 1965; Ndjeng and Brunet 1998 ). According to these authors the depth of the sedimentary series does not exceed 1500m. Therefore the boundary between the lower crust and the upper crust of Babouri-Figuil sedimentary basin would be shallow. In Mayo-Oulo-Léré sedimentary basin, two major discontinuities have been obtained on profiles P4, P5 and P6 (Fig. 8 ). The first discontinuity possesses the following depths 4.27km, 4.62km and 5.32km. These depths could correspond to the crust-mantle interface. The second discontinuity presents the following depths 1.48km, 1.54km and 1.72km. These depths are associated with intracrustal structures with an average depth of 1.55 km. This value probably corresponds to the near surface layer. It indicates that the Mayo Oulo-Léré basin would be deeper than that of Babouri-Figuil. 4.3. Density and Density Contrast of Structures To determine the characteristics and shapes of geological structures of suspected bodies in Babouri-Figuil and Mayo oulo-Léré sedimentary basins, six profiles were modelized. P1, P2 and P3 of SE-NW direction were modelized in Babouri-Figuil sedimentary basin and P4, P5 and P6 of SW-NE direction in Mayo Oulo-Léré. The average densities of sediments, granites and basaltic rocks present in the study area are respectively: 2.45g/cm 3 ; 2.65g/cm 3 ; 3g/cm 3 (Telord et al.1990). The corresponding density contrasts are respectively: -0.2g/cm 3 , 0g/cm 3 and 0.3g/cm 3 . In Babouri-Figuil sedimentary basin, we obtain three models of structures corresponding to profiles P1, P2 and P3. These models are constituted of two formations of different density contrast (Fig. 9 ). - The first formation has density contrast and density respectively − 0.2g/cm 3 and 2.45g/cm 3 . This formation is present throughout the profile. Its depth varies and reaches a spectacular value of 5km, this formation would probably be responsible for a vast zone of negative Bouguer anomaly observed in the sedimentary basin. The density contrast associated with this formation permits to identify along the continental sediments. - The second formation with density of 2.65g/cm 3 is associated to granites. It constitutes the substratum of the basin and it is presented as a rooted structure that extends to great depth. In Mayo Oulo-Léré sedimentary basin, we obtain three models corresponding to profiles P4, P5 and P6. These models are constituted of three formations of different density contrast (Fig. 10 ). - The first formation of density contrast − 0.2g/cm 3 has an average density of 2.45g/cm 3 . It is associated with continental sediments. This formation is present throughout the profile. It depth varies and reach a maximum depth of 3km. - The second formation with an average density of 2.65g/cm 3 is associated to granites. The depth is an extension of this formation probably constitutes the substratum of the basin. - The third formation with density contrast of + 0.3g/cm 3 has an average density of 2.95g/cm 3 . It is associated with basaltic rocks. To the SW of the profile, these basalts are near surface. The roof of this formation is decreasing and stabilizes at 1.5km. This roof drops to a depth of 3km to the NE of the profile. This formation would be formed during the cooling of magma inside the earth's surface during the volcanic eruption. 5. Discussion Empirical method of Zeng allows us to determine a regional anomaly which presents the best resemblance to the prolonged Bouguer anomaly at optimum altitude. This method testifies that the residual map of order 4 used in this work is an appropriate one. Negative anomalies observed on this residual map are due to the sedimentary cover while positive anomalies can be explained by the presence of basaltic rocks that were brought up tectonically to the surface. According to the spectral analysis, the depth in the negative anomaly (Babouri-Figuil) and positive anomaly (Mayo Oulo-Léré) is very close. This is because the two basins are similar and shallow. The mean depths of Babouri-Figuil and Mayo Oulo-Léré sedimentary basins were 1.50km and 1.55km respectively. These results agree with those obtained by (Ntsama 2013). According to these authors, Mayo Oulo-Léré and Babouri-Figuil are small shallow Cretaceous basins filled with continental sediments and which depths do not exceed 1600m. For 2.5D subsurface modeling, the structure of the Babouri-Figuil and Mayo Oulo-Léré presents many similarities in the composition of the upper crust when we observe profile P1 to P6. Some constraints and other geological considerations linked with the tectonic features of these basins were combined to build an accurate model for each profile. These constraints have been adopted to build the model corresponding to each anomaly such as the densities of anomalous masses. Densities have been either superior or inferior to the enclosing bed density, which was supposed to have homogenous mean density of 2.67g/cm 3 for the Babouri-Figuil and Mayo Oulo-Léré. The mean densities of rocks present in the study area like granites, basaltics rocks and sedimentary formations were respectively supposed to be 2.65; 3; 2.45 g/cm 3 (Telford et al. 1990 ; Zanga-Amougou et al. 2013 ). The interpretation of these models showed the presence of granites, basaltic rocks and sedimentary covers. Sedimentary formations have variable thickness with the maximum of about 5km found in Babouri-Figuil and around 3km in Mayo Oulo-Léré sedimentary basin. The outflows of these sediments confirm the hypothesis showed in geological map. The following formation is constituted of granites. These granites are very abundant in the study area and their thickness are increasing in Babouri-Figuil and decreasing in Mayo Oulo-Léré sedimentary basin. This could indicate that the uplift of granites is most significant in Babouri-Figuil. These models showed also basaltic rocks that generate positive residual anomaly. The origin of these rocks is found at great depth; it has cooled down and could not reach the earth’s surface. These results are compatible with the findings of (Kamguia et al. 2005 ) and the scheme proposed by (Ndjeng et al. 1988 ) to explain the mechanism of magmatologic establishment of lavas in the Babouri-Figuil and Mayo-Oulo-Léré. 6. Conclusions This work is based on the analysis and interpretation of combined gravity data of Babouri-Figuil and Mayo Oulo-Léré sedimentary basins. The obtained new gravity anomaly map shows different geological structures partially or totally masked by the sedimentary cover. This map shows strong link between positive anomalies with basaltic rise and between negative anomalies with sedimentary deposits. For the choice of the residual anomaly we used the empirical method of Zeng. This method shows that the residual Bouguer anomaly map of order 4 is the best for an interpretation of crustal structures. The spectral analysis carried out in Babouri-Figuil and Mayo Oulo-Léré sedimentary basins permit to determine the major discontinuities. The mean values of 1.50 km and 1.55 km are the new depth values obtained for future studies in these basins. The 2.5D modeling of the sources of residual anomalies highlights the structures having different densities or densities contrast. The various models show that Babouri-Figuil sedimentary basin is constituted of continental sediment which is situated on granitic environnement. The Mayo Oulo-Léré sedimentary basin is constituted of sediments, basaltic rocks and granitic basement. For the future investigation we will use the 3D inversion, Horizontal Gradient Analysis and Euler deconvolution methods to improve and consolidate our results. Abbreviations EGM2008 Earth Gravitational Model 2008 ORSTOM Office de Recherche Scientifique et Technique d’Outre Mer BGI Bureau Gravimétrique International NGIA National Geospatial-Intelligence Agency USA United States of America ICGEM International Centre for Global Earth Models Declarations Acknowledgments We would like to acknowledge the National Ge­ospatial-Intelligence Agency (NGIA) of USA and Bureau Gravimetrique International (BGI) for compiling and making available the dataset used in this work. Most of the figures in the paper were produced using Generic Mapping Tools software developed by Wessel and Smith for Exploration Geophysics. We also thank the anonymous reviewers for their helpful suggestions and comments. Authors Contributions BS, AB, VO and LY designed the study area, proposed the methodology, analyzed and interpreted the gravity data by using various advanced processing techniques in consultation with JK and EMD. The manuscript was jointly prepared by BS, AB, VO, LY, JK and EMD. All authors realized maps, discussed the results and contributed to the writing of the manuscript. All authors read and approved the final version of manuscript. Funding This study was supported by the personal fund of the authors. Availability of data and materials The terrestrial gravity and EGM2008 data use in this study are available respectively, at the BGI (Bureau Gravimétrique International): https://bgi.obs-mip.fr/dataproducts/ and ICGEM (International Centre for Global Earth Models): http://icgem.gfz-potsdam.de/home Conflicts of Interest The authors reveal that there are no conflicts of interest regarding the publication of this paper. References Abate Essi JM, Marcel J, Diab DA, Yene Atangana JQ, Abossolo Angue M, Mvondo Ondoa J (2019) Gravity Modeling of the Au-U Mineralized Crust at the North-Central Cameroon Illustrating Crutal Permeability. Nat Resour Res 29:473–497. https://doi.org/10.1007/s11053-019-09506-4 Abate Essi JM, Marcel J, Yene Atangana JQ, Diab AA, Dassou Fita E, Mbossi EF, Mvondo Ondoa J, Penaye J (2017) Interpretation of gravity data derived from the Earth Gravitational Model EGM2008 in the Center-North Cameroon: structural and mining implications. Arab J Geosci 10(130):1–13. http://doi.org/10.1007/s12517-017-2919-y Abdelrahman EM, Bayoumi AI, Abdelhady YE, Gobashi MM, El-Araby HM (1989) Gravity interpretation using correlation factors between successive least-squares residual anomalies. Geophysics 54(12):1521–1663. http://doi.org/10.1190/1.1442629 Abubakar AJ, Hashim M, Beiranvand AP (2018) Identification of hydrothermal alteration minerals associated with geothermal system using ASTER and Hyperion satellite data: a case study from Yankari Park, NE Nigeria. Geocarto Int 34(6):597–625. https://doi.org/10.1080/10106049.2017.1421716 Allix P, Grosdidier E, Jardiné S, Legoux O, Popoff M (1989) ) Découverte d’Aptien supérieur à Albien inférieur daté par des microfossiles dans la série détritique crétacée du fossé de la Bénoué (Nigéria). C R Acad Sci Paris 2(292):1291–1295 Allix P, Popoff M (983) Le Crétacé inférieur de la partie nord-orientale du fossé de la Bénoué (Nigéria): un exemple de relation étroite entre tectonique et sédimentation. Bull. Rech. Explor. Prod. Elf-Aquitaine 7: 349–359 Bessong M (2012) Paléoenvironnements et diagenèse dans un réservoir gréseux d’âge crétacé du fossé de la Bénoué au Nord Cameroun: les grès de Garoua. Thèse de Doctorat, Université de Poitiers Bonvalot S, Balmino G, Briais A, Kuhn M, Peyrefitte A, Vales N, Biancale R, Gabalda G, Moreaux G, Reinquin F, Sarrailh M (2012) WORLD GRAVITY MAP 1ST EDITION. Bureau Gravimetric international Bouba A, Kamguia J, Tabod CT, Yap L, Nouayou R, Kande HL, Oyoa V (2017) Subsurface Structural Mapping Using Combined Terrestrial and Grace Gravity Data of the Adamawa Plateau (North-Cameroon). Int J Géosciences 8(7):869–887. https://doi.org/10.4236/ijg.2017.87050 Brunet M, Dejax J, Brillanceau A, Congleton J, Downs W, Duperon-Laudoueneix M, Eisenmann V, Flanagan K, Flynn L, Heintz E, Hell J, Jacobs L, Jehenne Y, Ndjeng E, Mouchelin G, Pilbeam D (1988) Mise en évidence d’une sédimentation précoce d’âge Barrémien dans le fossé de la Bénoué en Afrique occidentale (Bassin du Mayo Oulo Léré, Cameroun), en relation avec l’ouverture de l’Atlantique Sud. C R Acad Sci Paris 306(II):1125–1130 Colin JP, Brunet M, Congleton JD, Dejax J, Flynn LJ (1992) Ostracodes lacustres des bassins d’âge crétacé inférieur du Nord Cameroun: Hamakoussou, Koum et Babouri-Figuil. Revue paleobiol 11(2):357–372 Cooper GRJ (2004) Euler deconvolution applied to potential field gradients. Explor Geophys 35:165–170. https://doi.org/10.1071/EG04165 Danra Moh Guela GB, Tchameni R, Daouda D, Fosso Tchunte PM, Awé S, Bisségué JC (2019) Geological Mapping of the Panafrican Mokong Gneisess and Granitoides (Far North Cameroon): Contribution of Semi-automatic Processing from Landsat 8 OLI/TIRS Images. J Geosci Geomatics 7(2):80–87. https://doi.org/10.12691/jgg-7-2-4 Dejax J, Michard JG, Brunet M, et Hell J (1989) Empreintes de pas de Dinosauriens datées du Crétacé inférieur dans le bassin de Babouri-Figuil (fossé de la Bénoué, Cameroun). J Geol Paleontology 1781:85–108 Dimitriadis K, Tselentis GA, Thanassoulas (1987) Comput Geosci 13(5):549–560. https://doi.org/10.1016/0098-3004(87)90056-2 . A basic program for 2-D spectralanalysis of gravity data and source-depth estimation Farhi W, Boudella A, Saibi H, Bounif MOA (2016) Integration of magnetic, gravity, and well data in imaging subsurface geology in the Ksar Hirane region (Laghouat, Algeria). J Afr Earth Sc 124:63–74. https://doi.org/10.1016/j.jafrearsci.2016.09.013 Gerard et Griveau (1972) Interprétation quantitative en Gravimétrie ou en Magnétisme à partir de la carte transformée de gradient vertical. Geophys Prospect 20(2):459–481. https://doi.org/10.1111/j.1365-2478.1972.tb00648.x Guiraud R, Maurin JC (1991) Le rifting en Afrique au Crétacé inférieur: synthèse structurale, mise en évidence de deux étapes dans la genèse des bassins, relations avec les ouvertures océaniques péri-africaines. Bull de Société Géologique de France 162(5):811–823. https://doi.org/10.2113/gssgfbull.162.5.811 Jitendra V, Pala SK (2015) Geological mapping of Jharia Coalfield, India using GRACE EGM2008 gravity data: a vertical derivative approach. Geocarto Int 30(4):388–401. https://doi.org/10.1080/10106049.2014.905637 Kamguia J, Manguelle-Dicoum E, Tabod CT, Tadjou JM (2005) Geological models deduced from gravity data in the Garoua basin, Cameroon. J Geophys Eng 2(2):147–152. https://doi.org/10.1088/1742-2132/2/2/009 Kamguia J, Tabod CT, Nouayou R, Tadjou JM, Manguelle-Dicoum E, Kande HL (2007) The local geoid model of Cameroon CGM05. Nordic J Surveying Real Estate Res 4(2):7–23. https://journal.fi/njs/article/view/1658 Louis P (1970) Contribution géophysique à la connaissance du bassin du lac Tchad. Mémoire OSTROM Paris 12:1–311 Ndjeng E (1992) Etudes de la sédimentation et du modèle géodynamique de deux bassins du Crétacé inférieur du Cameroun: Babouri-Figuil et Mayo Oulo-Léré. Thèse Doctorat ès Sciences, Université de Yaoundé Ndjeng E (1994) Pole des caractères exoscopiques des grains de quartz des grès de Garoua sur l’interprétation du paloéoenvironnement du bassin de la Bénoué du Crétacé supérieur.Ann. Fac. Sci HS Chim. Sci. Nat73–82 Ndjeng E, Brunet M (1998) Modèle d’évolution géodynamique de deux bassins de l’Hauterivien–Barrémien du Nord-Cameroun: les bassins de Babouri-Figuil et du Mayo Oulo-Léré (Fossé de la Bénoué). Géoscience au Cameroun, pp 163–165 Ndjeng E, Mouchelin G, Pilbeam D (1988) Mise en évidence d’une sédimentation précoce d’âge Barrémien dans le fossé de la Bénoué en Afrique occidentale (Bassin du Mayo Oulo Léré, Cameroun), en relation avec l’ouverture de l’Atlantique Sud. C R Acad Sci Paris 306(II):1125–1130 Nnangue JM, Ngako V, Fairhead JD, Ebinger CJ (2000) Depths to density discontinuities beneath the Adamawa plateau region, Central Africa, from spectral analyses of new and existing gravity data. J Afr Earth Sc 30(4):887–901. https://doi.org/10.1016/S0899-5362(00)00058-0 Noutchogwe TC, Tabod CT, Manguelle-Dicoum E (2006) A gravity study of the crust beneath the Adamawa fault zone, west central Africa. J Geophys Eng 3(1):82–89. https://doi.org/10.1088/1742-2132/3/1/009 Ntsama Atangana JA (2013) Magnétostratigraphie et sédimentologie des formations crétacéesn des bassins sédimentaires d'Hamakoussou et du Mayo Oulo-Léré au Nord-Cameroun (Fossé de la Bénoué). Thèse de Doctorat, Université de Poitiers Palvis NK, Holmes SA, Kenyon SC, Factor JK (2008) An Eath Gravitational Model to degree 2160: EGM2008. Presented at the EGU General Assembly, Vienna, Austria, April 13 2008 Palvis NK, Holmes SA, Kenyon SC, Factor JK (2012) The development and evaluation of the earth gravitational model 2008 (EGM2008). J Geophys Res 117(B4):1–38. https://doi.org/10.1029/2011JB008916 Poudjom-Djomani YH (1993) Apport de la gravimétrie à l’étude de la lithosphère continentale et implications géodynamiques: étude d’un bombement intraplaque: le massif de l’Adamaoua (Cameroun). Thèse de Doctorat, Université de Paris Sud, Centre d’Orsay, p 294 Saibi H, Nishijima J, Aboud E, Ehara S (2006) Euler deconvolution of gravity data in geothermal reconnaissance; the Obama geothermal area, Japan. J Explor Geophys Japan (Butsuri-Tansa) 59(3):275–282. https://doi.org/10.3124/segj.59.275 Talwani M, Worzel JL, Landisman M (1959) Rapid gravity computations for two-dirnensional bodies with application to the Mendocino Submarine fracture zone. J Geoplqs Res 64(1):49–59. https://doi.org/10.1029/JZ064i001p00049 Telford WM, Geldart LP, Sheriff RE, Keys DA (1990) Applied Geophysics, 4th edition of National Conference on geophysics, Cambridge University Press. Cambridge United Kingdom, 860 p Toushmalani R, Saibi H (2015) Fast 3D inversion of gravity data using Lanczos bidiagonalization method. Arab J Geosci 8(7):4969–4981. https://doi: 10.1007/s12517-014-1534-4 Weiyong Y, Rummel R (2013) A comparison of GOCE gravitational models with EGM2008. J Geodyn 73:14–22. https://doi.org/10.1016/j.jog.2013.10.004 Wessel P, Smith WHF (1995) New version of Generic Mapping Tools released. Eos Trans Am Geophys Union 76:329. https:/doi.org/10.1029/95EO00198 Zanga-Amougou A, Ndougsa-Mbarga T, Meying A, Layu Yufenyu D, Bikoro-Bi-Alou M, Manguelle-Dicoum E (2013) 2.5D Modeling of Crustal Structures along the Eastern Cameroon and Western Central African Republic Derived from Finite Element and Spectral Analysis Methods. Geophysica 49(1):75–97 Zeng H, Xu D, Tan H (2007) A model study for estimating optimum upward continuation height for gravity separation with application to a Bouguer gravity anomaly over a mineral deposit, Jilin province, northeast china. Geophysics 72(4):47–71. https://doi.org/10.1190/1.2719497 Supplementary Files GraphicalAbstract.jpg Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-1664918","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":107736652,"identity":"ab41a2dd-2cb9-402a-be5b-377743b83625","order_by":0,"name":"Bouba Saidou","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4UlEQVRIiWNgGAWjYBACAxCRwMbAYH+8+QCQKSFDvBaGM8cSQFp4iNPCANJyIwfMJqzFnP34ww8PymwSGxtyPr+6UWPBw8B++OgGfFose3KMJRLOpSU2M5zdZp1zDOgwnrS0G3gddiCHQSKx7XBiG2PvNuMcNqAWCR4z/FrOP3/8A6Slh5nnmXHOP2K03EgwA9syg42H+XFuGxFaLGe8MbMA+sV4Aw+bGXNunwQPGyG/mPOnP775o8xGdoP848efc77VyfGzHz6GVwsyYJMAk8QqBwHmD6SoHgWjYBSMgpEDANFbSjwvb0FIAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0002-9504-0966","institution":"University of Maroua: Universite de Maroua","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Bouba","middleName":"","lastName":"Saidou","suffix":""},{"id":107736653,"identity":"4bb753b1-dffc-4111-80c8-062204742979","order_by":1,"name":"Apollinaire Bouba","email":"","orcid":"","institution":"University of Maroua: Universite de Maroua","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Apollinaire","middleName":"","lastName":"Bouba","suffix":""},{"id":107736654,"identity":"bf9c4dc2-7b06-40a7-a028-2798a0a7b44a","order_by":2,"name":"Valentin Oyoa","email":"","orcid":"","institution":"University of Maroua: Universite de Maroua","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Valentin","middleName":"","lastName":"Oyoa","suffix":""},{"id":107736655,"identity":"28e40568-a1bf-4a67-9d9f-4d8a9ce10fd2","order_by":3,"name":"Loudi Yap","email":"","orcid":"","institution":"University of Yaounde I: Universite de Yaounde I","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Loudi","middleName":"","lastName":"Yap","suffix":""},{"id":107736656,"identity":"de5e17f1-16e1-4d9a-8597-6c355cba9d31","order_by":4,"name":"Joseph Kamguia","email":"","orcid":"","institution":"University of Yaounde I: Universite de Yaounde I","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Joseph","middleName":"","lastName":"Kamguia","suffix":""},{"id":107736657,"identity":"4ff394f9-7fed-4305-9de5-725fa6bac43f","order_by":5,"name":"Eliezer Manguelle-Dicoum","email":"","orcid":"","institution":"University of Yaounde I: Universite de Yaounde I","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Eliezer","middleName":"","lastName":"Manguelle-Dicoum","suffix":""}],"badges":[],"createdAt":"2022-05-17 10:02:52","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-1664918/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-1664918/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":22178597,"identity":"7db6f5ed-3e62-4ba0-a2bd-c40820ba8c46","added_by":"auto","created_at":"2022-06-02 14:26:38","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":540842,"visible":true,"origin":"","legend":"\u003cp\u003eLocation map of Babouri-Figuil and Mayo Oulo-Léré sedimentary basins, modified after (Bessong 2012).\u003c/p\u003e","description":"","filename":"fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-1664918/v1/d01726381907a2e06659d724.png"},{"id":22178604,"identity":"deddd3ab-6672-48f1-ae22-1349fab6f916","added_by":"auto","created_at":"2022-06-02 14:26:38","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":750638,"visible":true,"origin":"","legend":"\u003cp\u003eGeological map of the study area (modified from (Abubakar et al. 2018; Abate Essi et al. 2019): \u003cstrong\u003e1:\u003c/strong\u003e Mica Schist. \u003cstrong\u003e2:\u003c/strong\u003e Lower Gneiss. \u003cstrong\u003e3:\u003c/strong\u003e Sedimentary Formations. \u003cstrong\u003e4:\u003c/strong\u003e Embrechites Migmatic. \u003cstrong\u003e5:\u003c/strong\u003e Old Syn Tectonic Granitoid. \u003cstrong\u003e6:\u003c/strong\u003e Late Syn-tectonic Granitoid. \u003cstrong\u003e7:\u003c/strong\u003e Anatexites Granitoid. \u003cstrong\u003e8:\u003c/strong\u003e Post-Tectonic Granitoid \u003cstrong\u003e9:\u003c/strong\u003e Quaternary Alluvium. \u003cstrong\u003e10:\u003c/strong\u003e Cretaceous Benue Sandstone. \u003cstrong\u003e11:\u003c/strong\u003e Plio-pleistocene. \u003cstrong\u003e12:\u003c/strong\u003e Conglomerates (Sandstone and lavas). \u003cstrong\u003e13:\u003c/strong\u003e Anatexites Migmatic. \u003cstrong\u003e14:\u003c/strong\u003e Basalt.\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-1664918/v1/a90606647c1bdfeb91f5b876.png"},{"id":22178595,"identity":"34bea916-8bd8-4147-8fbb-0bc1bceb2992","added_by":"auto","created_at":"2022-06-02 14:26:37","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1996787,"visible":true,"origin":"","legend":"\u003cp\u003eBouguer anomaly map of the region obtained by using terrestrial gravity data\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"fig3.png","url":"https://assets-eu.researchsquare.com/files/rs-1664918/v1/25d1023262727a5cc24b12d6.png"},{"id":22178596,"identity":"f6d0c3b2-ae27-4525-8cac-abb8709a968e","added_by":"auto","created_at":"2022-06-02 14:26:37","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":2085887,"visible":true,"origin":"","legend":"\u003cp\u003eBouguer anomaly map of the region obtained after combined terrestrial gravity data and EGM2008 model.\u003c/p\u003e","description":"","filename":"fig4.png","url":"https://assets-eu.researchsquare.com/files/rs-1664918/v1/0b43b46c9a51a44744d3b1ac.png"},{"id":22179874,"identity":"46e2b592-6efc-4205-9dfe-4dcbece1986e","added_by":"auto","created_at":"2022-06-02 14:36:38","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":48582,"visible":true,"origin":"","legend":"\u003cp\u003eOptimum upward-continuation height by the method of (Zeng et al. 2007). \u003cstrong\u003e(a)\u003c/strong\u003e Cross-correlation between two successive upward continuated as a function of the continuation height, \u003cstrong\u003e(b)\u003c/strong\u003e the deflection C of the cross-correlation curve and \u003cstrong\u003e(c)\u003c/strong\u003e the factor of correlation according to the degrees of regional anomaly.\u003c/p\u003e","description":"","filename":"Fig5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1664918/v1/ecbfdc6ecab016afbd6ceba0.jpg"},{"id":22179303,"identity":"26ecf89c-6d50-4f8c-aa70-768e7b414ab3","added_by":"auto","created_at":"2022-06-02 14:31:38","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":2099381,"visible":true,"origin":"","legend":"\u003cp\u003eFourth-order of residual Bouguer anomaly map of the region obtained after combined terrestrial gravity data and EGM2008 model.\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"fig6.png","url":"https://assets-eu.researchsquare.com/files/rs-1664918/v1/b188bb8f476fc98b782dde2f.png"},{"id":22179302,"identity":"1e3bcd9c-7674-4487-a039-b107e45a8377","added_by":"auto","created_at":"2022-06-02 14:31:38","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":48340,"visible":true,"origin":"","legend":"\u003cp\u003ePower spectrum of profiles P1, P2 and P3 from spectral analysis program of Babouri-Figuil basin.\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"Fig7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1664918/v1/b50f763bae8924eeefcbe7a0.jpg"},{"id":22179873,"identity":"8df05e53-79f6-48e1-bfd9-c0ee7f49e8ee","added_by":"auto","created_at":"2022-06-02 14:36:38","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":47778,"visible":true,"origin":"","legend":"\u003cp\u003ePower spectrum of profiles P4, P5 and P6 from spectral analysis program of Mayo Oulo-Léré basin.\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"Fig8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1664918/v1/87fd956e3cddb269a4bb514d.jpg"},{"id":22178600,"identity":"250b8ddb-0d3d-459e-811e-dc7e4cc8069e","added_by":"auto","created_at":"2022-06-02 14:26:38","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":76181,"visible":true,"origin":"","legend":"\u003cp\u003eCrustal model of profile P1, P2 and P3 of Babouri-Figuil basin\u003c/p\u003e","description":"","filename":"Fig9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1664918/v1/1c7cedf790a57f10ac4bf8df.jpg"},{"id":22180809,"identity":"0095096a-6722-4e9c-962b-234af4aed3e7","added_by":"auto","created_at":"2022-06-02 14:41:38","extension":"jpg","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":97277,"visible":true,"origin":"","legend":"\u003cp\u003eCrustal model of profile P4, P5 and P6 of Mayo Oulo-Léré basin\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"Fig10.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1664918/v1/5872e5d1624f5cd65c080a1d.jpg"},{"id":28403016,"identity":"8abb538f-0c23-418e-9837-fdad67435ca8","added_by":"auto","created_at":"2022-10-29 13:44:35","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":7600651,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-1664918/v1/b52f77b9-c895-4e2e-9bb7-eb92e0b12601.pdf"},{"id":22179305,"identity":"9f4e3971-0802-4cca-b9a6-2e7bcba3305c","added_by":"auto","created_at":"2022-06-02 14:31:38","extension":"jpg","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":1169477,"visible":true,"origin":"","legend":"","description":"","filename":"GraphicalAbstract.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1664918/v1/9cd1a04b9fd453e9f8175701.jpg"}],"financialInterests":"","formattedTitle":"Gravity Study of the Crust beneath the Babouri-Figuil and Mayo Oulo-Léré Sedimentary Basins, North Cameroon and South Chad","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe study area located between longitudes 13\u0026deg; to 14\u0026deg;30E and latitudes 9\u0026deg; to 10\u0026deg;30N is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e1\u003c/span\u003e. It covers the Babouri-Figuil and Mayo Oulo-L\u0026eacute;r\u0026eacute; sedimentary basins. The main studies carried out in these basins have mainly focused on geological studies. These include the works of (Allix et al. 2000; Allix and Popoff 1983; Dejax et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e1989\u003c/span\u003e; Ndjeng et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e1988\u003c/span\u003e; Ndjeng \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Colin et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Ndjeng \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e1994\u003c/span\u003e; Brunet et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e1988\u003c/span\u003e; Bessong \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Ntsama 2013). These works have shown that the Babouri-Figuil and Mayo Oulo-L\u0026eacute;r\u0026eacute; sedimentary basins are two small Wealdian basins filled with continental sediments. These sediments are mostly detritics and made up of an alternation of fine sandstones, silts and indurated marls. However, from geophysical point of view in general and gravimetry in particular, the thickness of these basins is still poorly understood. The gravity data available in this area are obtained by ORSTOM (Office de Recherche Scientifique et Technique d\u0026rsquo;Outre Mer) during the various reconnaissance campaigns. The itineraries followed tracks, carrossables roads and sometimes water courses. Despite these efforts, these data are very sparse and present many gaps. A Bouguer anomaly map realized with such gaps presents many insufficiencies. Its interpretation leads to erroneous conclusions. To solve this problem, it would be appropriate to densify data by carrying out a new gravity campaign. Unfortunately, gravity campaigns are very expensive. An elegant solution to this problem consists to densify the measured gravity data by using the EGM2008 field model and making them usable (Bouba et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). These data have been reduced by using a series of corrections to eliminate the non-geological causes of gravity variations. The obtained database allowed to establish a new gravity map of the region. In this paper, we applied spectral analysis and 2D.5 modeling methods to the combined gravity data in order to determine the depth and density contrast of the crustal structure beneath the Babouri-Figuil and Mayo Oulo-L\u0026eacute;r\u0026eacute; sedimentary basins. These methods have been used to isolate causative bodies by representing them as polygonal bodies in two dimensions (Toushmalani and Saibi \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Similar approaches were used successfully to improve the subsurface structure geometry of Algeria (Farhi et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Saibi et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2006\u003c/span\u003e) mentioned the relationship between the observed gravity anomalies and the obtained models of the integrated 2D gravity interpretation technique.\u003c/p\u003e"},{"header":"2. Geological Setting","content":"\u003cp\u003eCameroon has two types of sedimentary basins: coastal sedimentary basins located in the southwest of Cameroon and intracontinental sedimentary basins located in the northern part of the country. Many of these latter are connected to the Yola branch belonging to the Benue ditch. These are Koum, Hamakoussoum, Babouri-Figuil and Mayo Oulo-L\u0026eacute;r\u0026eacute; basins. The Babouri-Figuil sedimentary basin and that of Mayo Oulo-L\u0026eacute;r\u0026eacute; are small basins elongated of EW direction. They are located respectively between latitudes 9\u0026deg;44'-9\u0026deg;50' and 9\u0026deg;39'-9\u0026deg;44' and longitudes 13\u0026deg;44'-14\u0026deg;02' and 13\u0026deg;43'-14\u0026deg;28' (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e2\u003c/span\u003e). These two basins have Wealdian facies equivalent to the Bima formations in Nigeria (Ntsama 2013).\u003c/p\u003e \u003cp\u003eThe Babouri-Figuil sedimentary basin is the most northern of the small Cretaceous basins with continental sediment in north Cameroon. It is lengthened on nearly 45km with a width ranging from 1km towards Figuil and 8km between the villages of Babouri and Sorawel (Ndjeng et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e1988\u003c/span\u003e; Ntsama 2013). It is a basin dotted with mounds and basic sandstone. Its sedimentary pile locally reaches 1500m (Danra Moh Guela et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). These sediments are constituted of fine sandstones, silts and marls. Their presence testifies the sedimentation whose origin would be linked to the indicator of many emersion phases (Ndjeng \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e1992\u003c/span\u003e). The abundance of flore and the existence of evaporation levels are present throughout the basin. The swamp environment under hot and humid climate is revealed by the abundance of Estheries whose eggs dissemination is favored by drying seasonal periods (Brunet et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e1988\u003c/span\u003e). The presence of leaves and footsteps of dinosaurs have been found in Mayo-Tafal (Dejax et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e1989\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe Mayo Oulo-L\u0026eacute;r\u0026eacute; basin is over 50km long and less than 10km wide. It extends towards the south of Chad in the L\u0026eacute;r\u0026eacute; area. It is separated from the Babouri-Figuil basin by granite complexes culminating at 800m of altitude. It consists mainly of silts and hardened clays. Basaltic rocks present in the sediments in form of sills set up a metamorphism of contact (Ndjeng \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e1994\u003c/span\u003e). Through on Paleoflore study, the Mayo Oulo-L\u0026eacute;r\u0026eacute; sedimentary basin is constituted with invisible small grabens (Ntsama 2013; Guiraud and Maurin \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1991\u003c/span\u003e). These grabens established in north-south extensive context are constituted with basaltic formations (Ndjeng \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e1992\u003c/span\u003e). Microfossils collected from this basin provides from anteaptian sedimentation.\u003c/p\u003e"},{"header":"3. Data And Methods","content":"\u003cdiv class=\"Section2\" id=\"Sec4\"\u003e\n \u003ch2\u003e3.1. Gravity Data\u003c/h2\u003e\n \u003cp\u003eThe gravity data used in this work provide from two independent sources. One is derived from measured gravity data and the other is obtained from Earth Gravity Model EGM2008.\u003c/p\u003e\n \u003cdiv class=\"Section3\" id=\"Sec5\"\u003e\n \u003ch2\u003e3.1.1. Terrestrial Gravity Data\u003c/h2\u003e\n \u003cp\u003eThe terrestrial gravity data used in this work were collected between 1960 and 1968 by the Office de Recherche Scientifique et Technique d\u0026apos;Outre-mer (ORSTOM) during various reconnaissance campaigns. These data were obtained between latitudes 9\u0026deg;00\u0026apos; and 10\u0026deg;30\u0026apos;N and longitudes 13\u0026deg;00\u0026apos; and 14\u0026deg;30\u0026apos;E. The acquisition campaigns of these data were obtained by a car, along the roads, carossable tracks and sometimes water courses. The measurements were taken every 3km. Several gravimeters (Worden and Lacoste \u0026amp; Romberg) were used to measure the variations of gravity. The calibration of the gravimeters was carried out on stations of the Martin network which are defined in Potsdam system. The precision on the gravity values is the order of 0.2mGal. The location of the measuring stations was determined on topographic maps by compass tracking. The average error in the position of the stations is estimated at around 200m. Altitudes were estimated using barometers and altimeters (Wallace and Thierman, Thommen). The accuracy on the values of altitude depends on the climate, the difference of altitude between the reference station, the measure point and the distance from the stations. The error on altitude of the stations can reach 10m when the weather conditions are unfavorable and 3m otherwise.\u003c/p\u003e\n \u003cp\u003eThe terrestrial Bouguer anomaly map presented in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e is plotted using the Generic Mapping Tools (Wessel and Smith \u003cspan class=\"CitationRef\"\u003e1995\u003c/span\u003e). This map shows two main zones of anomalies: low and high zones.\u003c/p\u003e\n \u003cp\u003eLow anomalies zones are divided into two parts. The first part located in the northern part of the study area covers the towns of Hamakoussou, Dembo, Dourbey, Guider and the entire sedimentary basin of Babouri-Figuil. In this sector, low anomalies are unevenly distributed (-65 to -35mGal). This situation would be due to the lack of terrestrial gravity data in the sector. The second part located in south of L\u0026eacute;r\u0026eacute; is also constituted of low anomalies with a minimum that can reach \u0026minus;\u0026thinsp;60mGal. These anomalies would be due to the filling effect of the Pala-Lam\u0026eacute; sedimentary basin in Chad.\u003c/p\u003e\n \u003cp\u003eHigh anomalies zone covers the southwest of Garoua, Lagdo and Bib\u0026eacute;mi towns and the entire area of Mayo Oulo-L\u0026eacute;r\u0026eacute; basin. The amplitude of these anomalies is around \u0026minus;\u0026thinsp;25mGal with a maximum at 0mGal in the northern part of Bib\u0026eacute;mi and Mayo Oulo-L\u0026eacute;r\u0026eacute; sector. These anomalies would be due either to the upwelling of magmatic fluids through the lithospheric fractures in the sedimentary zone or to denser rocks found on surface (Louis \u003cspan class=\"CitationRef\"\u003e1970\u003c/span\u003e).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv class=\"Section3\" id=\"Sec6\"\u003e\n \u003ch2\u003e3.1.2. Data from EGM2008\u003c/h2\u003e\n \u003cp\u003eIn this part, gravity data were obtained using the Earth Gravity Model. This model provides more informations on the Earth\u0026apos;s gravity field for various geophysical applications (Palvis et al. \u003cspan class=\"CitationRef\"\u003e2008\u003c/span\u003e; Bonvalot et al. \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e). Its utilization is advantageous because it possesses: (1) harmonic coefficient up to degree and order 2190 (Weiyong and Rummel \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e). (2) Good spatial resolution and good ability to provide gravity data. (3) Spatial resolution of 5 arcminutes corresponding to a wavelength of 9km, approximately 6 times more resolution than other models. (4) Gravity data over the entire Earth, data obtained from disturbance analyzes of satellite trajectories and data from satellite altimetry over the oceans (Palvis et al. \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e). (5) Gravity data are freely obtained. (6) It provides more information on the areas devoid gravity data and geologically inaccessible. This model has been used in the localization of coal deposits in India, in the mapping of cratons and in the delineation of geological discontinuities in sedimentary basins (Jitendra and Pala \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e). According to (Bouba et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e; Kamguia et al. \u003cspan class=\"CitationRef\"\u003e2007\u003c/span\u003e; Abate Essi et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e) EGM2008 gravity data and terrestrial ones have the same precision; so they are stackable and can be superimposed. Data from this model are combined with terrestrial data in order to increase their density. Bouguer\u0026apos;s correction is obtained by taking an average density of 2.67g/cm\u003csup\u003e3\u003c/sup\u003e. The densified gravity data thus obtained have permitted to establish a new Bouguer anomaly map by joining points having the same anomaly value (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). For objectivity reasons, the Bouguer anomaly map is plotted by computer using the Generic Mapping Tools software (Wessel and Smith \u003cspan class=\"CitationRef\"\u003e1995\u003c/span\u003e). This map is interpreted in two gravity zones.\u003c/p\u003e\n \u003cp\u003eThe first zone located in the northern part of the study area, consists of a large low domain (-60mGal) visibly more developed than on terrestrial simple Bouguer anomaly map. It is in this area that Babouri-Figuil sedimentary basin is located. The Examination of this map shows that this basin tends to evoke the mark of sedimentary fill. We would imagine a lake basin where water courses brought their alluvium while the volcanoes spread their lavas. These anomalies may be due either to the collapse of sedimentary block or to the local thickening of sedimentary series generated by the depression of the basement roof. In south of L\u0026eacute;r\u0026eacute;, we observe negative anomalie zone of -60mGal. These anomalies can be due to sediments deposits in this area.\u003c/p\u003e\n \u003cp\u003eThe second zone extends from Garoua town to L\u0026eacute;r\u0026eacute; in Chad and up to Bib\u0026eacute;mi. This zone includes the Mayo Oulo-L\u0026eacute;r\u0026eacute; sedimentary basin. It is characterized by high and positive anomalies. These anomalies could correspond to the intrusion of basaltic rocks under the sedimentary basin. However, the orientation of the isoanomal lines does not coincide perfectly with the basin direction. It suggests that, the intrusion would have been favored by tectonic process. The first and second domains are separated by strong gradient, which would result from discontinuities between crustal formations, such as faults, flexures or contacts of intrusive rocks.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv class=\"Section2\" id=\"Sec7\"\u003e\n \u003ch2\u003e3.2. Method\u003c/h2\u003e\n \u003cdiv class=\"Section3\" id=\"Sec8\"\u003e\n \u003ch2\u003e3.2.1. Regional/Residual separation\u003c/h2\u003e\n \u003cp\u003eIn Benue sedimentary trough, the third-order of polynomial surface of regional anomaly has used (Kamguia et al. \u003cspan class=\"CitationRef\"\u003e2005\u003c/span\u003e). Such choice cannot be justified when we considered detailed interpretation of the basement. It is therefore necessary to define a criteria for choosing the regional surface which takes into account the variations of the gravity field in all directions. In this study we used the empirical method of (Zeng et al. \u003cspan class=\"CitationRef\"\u003e2007\u003c/span\u003e). This method permits us to determine a regional anomaly which presents the best resemblance to the prolonged Bouguer anomaly at optimum altitude. The degree of resemblance between two gravity fields g\u003csub\u003e1\u003c/sub\u003e and g\u003csub\u003e2\u003c/sub\u003e is determined by the correlation factor calculated by using the formula proposed by (Abdelrahman et al. \u003cspan class=\"CitationRef\"\u003e1989\u003c/span\u003e):\u003c/p\u003e\n \u003cdiv class=\"Equation\" id=\"Equ1\"\u003e\n \u003cdiv class=\"EquationNumber\"\u003e\u003cimg src=\"data:image/jpeg;base64,/9j/4AAQSkZJRgABAQEAYABgAAD/4RD6RXhpZgAATU0AKgAAAAgABAE7AAIAAAAQAAAISodpAAQAAAABAAAIWpydAAEAAAAgAAAQ0uocAAcAAAgMAAAAPgAAAAAc6gAAAAgAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFNhY2hpbiBNYWhhcm51cgAABZADAAIAAAAUAAAQqJAEAAIAAAAUAAAQvJKRAAIAAAADMTEAAJKSAAIAAAADMTEAAOocAAcAAAgMAAAInAAAAAAc6gAAAAgAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAADIwMjI6MDY6MDIgMTQ6MTA6MTMAMjAyMjowNjowMiAxNDoxMDoxMwAAAFMAYQBjAGgAaQBuACAATQBhAGgAYQByAG4AdQByAAAA/+ELImh0dHA6Ly9ucy5hZG9iZS5jb20veGFwLzEuMC8APD94cGFja2V0IGJlZ2luPSfvu78nIGlkPSdXNU0wTXBDZWhpSHpyZVN6TlRjemtjOWQnPz4NCjx4OnhtcG1ldGEgeG1sbnM6eD0iYWRvYmU6bnM6bWV0YS8iPjxyZGY6UkRGIHhtbG5zOnJkZj0iaHR0cDovL3d3dy53My5vcmcvMTk5OS8wMi8yMi1yZGYtc3ludGF4LW5zIyI+PHJkZjpEZXNjcmlwdGlvbiByZGY6YWJvdXQ9InV1aWQ6ZmFmNWJkZDUtYmEzZC0xMWRhLWFkMzEtZDMzZDc1MTgyZjFiIiB4bWxuczpkYz0iaHR0cDovL3B1cmwub3JnL2RjL2VsZW1lbnRzLzEuMS8iLz48cmRmOkRlc2NyaXB0aW9uIHJkZjphYm91dD0idXVpZDpmYWY1YmRkNS1iYTNkLTExZGEtYWQzMS1kMzNkNzUxODJmMWIiIHhtbG5zOnhtcD0iaHR0cDovL25zLmFkb2JlLmNvbS94YXAvMS4wLyI+PHhtcDpDcmVhdGVEYXRlPjIwMjItMDYtMDJUMTQ6MTA6MTMuMTA3PC94bXA6Q3JlYXRlRGF0ZT48L3JkZjpEZXNjcmlwdGlvbj48cmRmOkRlc2NyaXB0aW9uIHJkZjphYm91dD0idXVpZDpmYWY1YmRkNS1iYTNkLTExZGEtYWQzMS1kMzNkNzUxODJmMWIiIHhtbG5zOmRjPSJodHRwOi8vcHVybC5vcmcvZGMvZWxlbWVudHMvMS4xLyI+PGRjOmNyZWF0b3I+PHJkZjpTZXEgeG1sbnM6cmRmPSJodHRwOi8vd3d3LnczLm9yZy8xOTk5LzAyLzIyLXJkZi1zeW50YXgtbnMjIj48cmRmOmxpPlNhY2hpbiBNYWhhcm51cjwvcmRmOmxpPjwvcmRmOlNlcT4NCgkJCTwvZGM6Y3JlYXRvcj48L3JkZjpEZXNjcmlwdGlvbj48L3JkZjpSREY+PC94OnhtcG1ldGE+DQogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIAogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIAogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIAogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIAogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIAogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIAogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgIDw/eHBhY2tldCBlbmQ9J3cnPz7/2wBDAAcFBQYFBAcGBQYIBwcIChELCgkJChUPEAwRGBUaGRgVGBcbHichGx0lHRcYIi4iJSgpKywrGiAvMy8qMicqKyr/2wBDAQcICAoJChQLCxQqHBgcKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKir/wAARCAB6AjMDASIAAhEBAxEB/8QAHwAAAQUBAQEBAQEAAAAAAAAAAAECAwQFBgcICQoL/8QAtRAAAgEDAwIEAwUFBAQAAAF9AQIDAAQRBRIhMUEGE1FhByJxFDKBkaEII0KxwRVS0fAkM2JyggkKFhcYGRolJicoKSo0NTY3ODk6Q0RFRkdISUpTVFVWV1hZWmNkZWZnaGlqc3R1dnd4eXqDhIWGh4iJipKTlJWWl5iZmqKjpKWmp6ipqrKztLW2t7i5usLDxMXGx8jJytLT1NXW19jZ2uHi4+Tl5ufo6erx8vP09fb3+Pn6/8QAHwEAAwEBAQEBAQEBAQAAAAAAAAECAwQFBgcICQoL/8QAtREAAgECBAQDBAcFBAQAAQJ3AAECAxEEBSExBhJBUQdhcRMiMoEIFEKRobHBCSMzUvAVYnLRChYkNOEl8RcYGRomJygpKjU2Nzg5OkNERUZHSElKU1RVVldYWVpjZGVmZ2hpanN0dXZ3eHl6goOEhYaHiImKkpOUlZaXmJmaoqOkpaanqKmqsrO0tba3uLm6wsPExcbHyMnK0tPU1dbX2Nna4uPk5ebn6Onq8vP09fb3+Pn6/9oADAMBAAIRAxEAPwD6RooooAKKKKACiiigAooooAKKKKACiiigAooooAK5abWbmy+I0ltcXzf2U2lvL5LImI5o3j3YIXccrKnBJ6jGK6muZfwTHKyz3GtanNfRmYw3r+R5kXmFCcARBDjy127lbH4Lhdb+v5W/4I9NmT+FNRvtagvNUvC0NvNcPFaWpCny442KbiQMlmYEnkgDbjuTv1Q0PSU0LQrPS4bia5jtIhEks+zeyjpnaqjOPYfnV+qZKOb8bajqGk6TBf6VNIJLacTTW6qpFxAgLSqcqSDsViNuDuCjOCauaaLm412/vRqk8+nkRxwWhSLykbaGZ1YIHOcjqxGd3tieXSTNrqajJf3TRLbtALErF5PzEEt9zfu4A+9j260/RdItdB0a20zT/M+z2ybI/Mcs2M9yetJDZeooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigDgvir8LNN+JehCNytrq9qpNleY+6f7j+qH8x1HcHg/hpceFLvU28FfEPwR4f07xZZ/Ipk0qBUv1HR1O3G7Azxweo7ge815v4t8L6X8SfG2n2rWn7vw9Os15qkbFH3/eW1Rhgk/dZj/CMAfM2VI6St0e/wDn/W/qEtY+a2/yNW8+Fvhf+2NI1XRtE0/Sr3TLtZ1ks7dYN64IZWCAA9e47ds1b8f+AdJ+IfhqTStYTY65e2ukHz28mOGHqPUdx+BHUUUmk1yv+v6sNNp3PnXwLFoHhLxEvgD4reEtBW+B26ZrMmmQmO+TOFDOV5b0Y9ejfN19S1/4SeENV05Y7Dw9pem3kMyTQXNpaJAyMrA8lAMg4xg5HPSqnxJ0HT/iFNbeDmtFmnRkurq+xzp0Weqn/npJgqq9MAsRhQD3tpaxWNlBa2+7yoI1jTe5c7QMDLHJJ46nmqTbjd73+/z9SWknZbfkTVzL/EXwrFPKkmqqkMEphlvWgkFpHIOCjXO3yg2eMFs54robvyvsc32mTy4fLbzH37dq45Oe3HevDfCUGlazomn+CdV8ULpumQXIkh0O6sDaX10iyb40eZm2yZIBPlLk/wB6lHWVhvSNz3G0vLbULOK7sLiK6tplDxTQuHR1PQhhwR9K57T9Sm8S+KtQW2uZIdL0O4FswibH2q52hm3HrsTcowDy27OQAK0tN1qS/wBd1bTpLF7Yac0QSV5Fbzw653AD7o4I5546CuV+HMi6PD4zt9Qdkls9eu7mbKkkRSBZUbA5IKnPFCau35X/ABX+Ya2072/B/wCRuTfELwnBHrDy67aBdEx/aBDE+QSSAvHVsgjaMnPGM1u2d3Bf2MF5aP5lvcRrLE+CNysMg4PI4PevNL/UtKb4qeG/FkIEumarYy2UNyqN++lC+bEwXGSdpkRc85JAHr302v2Ftc6lFPKqDTLZbm5cSI5jQhjyikuOEJ5UA54J5wbRvL/hrf0n5Bu9P6/p3XmadYVl428OakmrPp+rQXSaOCb5oMuIRgnqB83Cn7uelXdD13TfEui2+raHdrd2NypaKZQRuwSDwQCCCCMEZriIfPt/jh4jtLIMkup6PZyecq5Ee15ULntkDpnqcD1oad+Xrr9+/wCg1a1/T87Hf2F9bappttf2EomtbqJZoZVzh0YZB59Qa57xXqVx4Vng8Qm6lfS/Nit9QtH+ZI0dwgnQ4ypUsNw6Fc8ZGa2bi6stA0+0hOyOIyRWlvGZUQsSQqqC7DJA5xksQDgE8HmfjAjT/CnWbSIFp7xY7WBB1eSSVFVR9SRQ97x7/wBIUVfR/wBeZ1Gr61p2gaY+oaxeR2lqhAMkh6knAAA5JJ6Acms+w8b+HdQ1BLCPUltr+Q/u7G/je0uJOM5WKYK7Dg8gY4PpXMfFWKKDQ9AuHluBf6fqMVxbPFbtcojIpDSSwr87xqCc7eQSvI61J4OFnqmoan4vsPENr4q1ma3S0VLQC2htowSyxeWWdo8sSWLlm44HYitr5f1/X9IWtl5neXVzDZWc11dSCOCCNpJHPRVAyT+QrB8I3V3rOlx+JNQmljXUohLbWZbEdtAeUyO7kYLE5wTgYA5zdTvNQ8WfD7xZpcmniy1eCC4sZLeKYzI0jQhkKPtUsGWROqggkjHHNrw14g0yw+E+j61eXIi0+HTIGlmKk7AEVTkAE8Hg+lC6v0/G/wDkN9F6/hb/ADHN8TPBq6NLqw8QWj2MV2LJpoyX3THGEUAEscEHKgjGT0Brqa810qSz0z42ahcSQ7E8Q6fFPZNtJLvG/lyEADALKY2J67VBPt10/jDRrPwtceIr66WDS7Z3WSdWWcALIY8jyi+ckdOo7gEEA05U/wCu35hZ3t/Wuv5G1LLHBC8szrHHGpZ3c4Cgckk9hXPw+PvC9z4au/EFvrEM2k2Uphnu41ZkRgQOwyR8y8jI5rbsr231GwgvbGZZ7a4jWWGVDkOjDII+oNedeE7Z5vF3jzQljZbebWFuJ3A+Xy5IIyy59WPH0JPYU0vecX2/Vf5hpZPz/RnpgORkciuW1PU7jwx4rsGuruSfSdbuRaCOXn7HcFSUKtjOx9pUqc4YrjAJFbzalbrrMelhkNy8DTlBKm5EDBQSm7fgk8EKR8pyQcZ5H4owyXtr4ZsLbJuJ/ENm0YXriMmR2+gVGP4Ul8UfNpfe7MPsv0b/AAudzRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAeb/F34q6f8PdPtrJpZhqOonCG3jWR7eLOGlCsQpYdFBOCevAIrjdJ/aV+HuiaXDp+n6P4hSCIHG6CFmdicszEzZZmJJJPJJJr3aeYW9vJM+SsaFzhSTgDPQAk/gCawh458PWumafc65rmlaXLfWyXMcVzeLFuVhnKiUIxHuVB9QOlJaX/AK9P1GzzKD9onSvF3iDR/D3hTTdShudQvoYpLi8VEEce8F8BHYklQR2xnPbFd38T/iNYfDfwsdQuh5t5cN5VnbgZ8x+5PI+VRyeR2Gea0tP8RvqfioW1jLYXWjzaf9qtru2m80ysJNjcj5do9iec9OldDTesfv8A8v0Yk/e/r1/VHz9oH7R/gLQtPMK6f4jubmZzNd3cttBvuZSBudsTewAA4UAAcAVPq37UGhahp72PhfSdV/tO6/cQPdpGiRs3yh/ldicZzjHOOor1+78WaTpuoXsOr39pp1vZrCHuLyUwqXk3ELudQh4XgqzHOQQMc0LrxraXbac/hTUdI1e3k1CK1vZILsSmFXzjATI3EjuRxnrTTTav5f5A7pN+r/U0PE3h1fEvhxtLkvJrRt8UqTxAMVeN1dSQ2Qw3KMg9az7jwvq+tpBb+LNXsL2yhniuBDZaYbdneNg67meWTjIBO0KffGRXVUUtncOljC0uw1S38Xaze3cNmtjdrCLdorhnlOwEHchjAXOezN0qefQlPiGLWbK5e0udgiulVQUu4x0Dj+8uTtYEEZIOQcVrUUAFZGnabeRaprN3eSRq15Ki2zwtuaOFUAUHcuAdxdscj5q16KAMy70u5XQLiy0K/wD7Ou5AxjvHhE5SRm3M5QkBiSTxwOatWdmLbdJK/nXUoHmzlcFsZwAOyjJwO2SeSSTZooA5y+vYNX8WWWkWsnmNpsxur5QOIyI/3Stn+8ZAw/65n0OL11oa6hrltf387TQ2Z8y1tNuEjlwR5rd2YAkDsM5xnBGrRQtAOZ1LwxqTeKn8QaBrENldTWiWk8N7Zm5hZEZmUqFkjZWy7fxYPpS23h/UNOm1LW0ls9R8RXlukAd4za2+1CxVcL5jgZckklyemQMY6WijpYd9bmJ4Yt9Zt7CQeIILGK5Z9zNZ3DTeax+87M0ceOwC7TgKOT2l0nQl0W9uzY3LrYXLmUWLKCkEhOWMZ6qrHJKnIycjGSDrUUdbkjZfM8l/JCmTadgY4BPbJ9Ky9D0q5sPC1pp93Psu1jH2ia3IO6Unc7Asvdix6Z5rWooGZd9pl4NLtbPw/fppX2eSP5mtxOGiU8x4JGMjjdnIq7a2sdnGwTLM7b5ZG+9I2MbmPrgAegAAGAAKnooA5zw/ewa/rV7rllJ51j5MdraSgfK+MvIy9/vMqn3jI7Vej0NW8QtrF9O11cRo0VohXalqjY3bR3ZsDLHsMDAznVooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiimedGJxCZE80qXEe4bioOCcemSPzoAfRRTIpo54llgkWSNhlXRgQfoRQA+iiigAooooAK4CH4j6pLdXtnF4Xa+urPVY9PkXTrszIiMVDTMzRpgKXxjB5VuQFLDvJmdIHaKPzHVSVQEDcccDJrkvAGit4P8BiXX/Ktb+Yy6hqsryAhJXJd8tkjCg4znHy5oW93t/wf8k7j6WW/wDX/AOworH0XxTpfiC6urfTTeGW02+cLiwntwu4ZGDIig5HPGeMHvT9c8S6X4chWTVZpU3KzhILaSeQquNzbI1Ztq5GWxgZGTzSbSV2Ja7GrUN5dR2NnLczLM0cS7mEELyuR7IgLMfYAmm2F7DqWnwXtr5nkzoJI/NiaNip6ZVgGH0IFOvIJLmzlhhuprOR1ws8AQvGfUB1Zc/UEU3dArMwf+E80j/nz8Qf+E5qH/xit2yu47+ziuoFmWOVdyrPA8Lge6OAyn2IFYX/AAi+r/8AQ9+IP+/Gn/8AyLWzHYH+yDYXl5dXZaIxSXLOIpnBGCd0QTa3PVQuOowaALdFc3/wgekf8/niD/wo9Q/+P1h+JPD1tpDaVb6UmsX13qd6bSNLnxdqVvGmIJZixZXc9ISMbepoA9Aorzb/AIRHxB/0Cf8AzIOrf/GqP+ER8Qf9An/zIOrf/GqAO71uwm1TQr2wtrr7JLdQNEs+zf5e4YzjIz19RVS/8LWGpCD7TNqUXkRCJVstUurRcD1WKRQfqcn3rj/+ER8Qf9An/wAyDq3/AMao/wCER8Qf9An/AMyDq3/xqgDqLLw1c6f4ngv7fUQ2nw2RtBbXCSzznL79xuHlJPPYqeO9bd5cfY7Ge5MUs/kxtJ5UKbnfAzhR3J7CvPP+ER8Qf9An/wAyDq3/AMao/wCER8Qf9An/AMyDq3/xqjW1v67hpc6PT9FXWtOvbnVFvrU6jeG5VIbqa0lWNVCRgmNldcooYoTwWORkVHeeC3SG0j0PVJ4PJvYruU6nNc6iX2ZwqmSfKZzyRn6Vgf8ACI+IP+gT/wCZB1b/AONUf8Ij4g/6BP8A5kHVv/jVG23l+At1r/Vz0mivNv8AhEfEH/QJ/wDMg6t/8ao/4RHxB/0Cf/Mg6t/8aoGek0V5t/wiPiD/AKBP/mQdW/8AjVH/AAiPiD/oE/8AmQdW/wDjVAHpNFebf8Ij4g/6BP8A5kHVv/jVH/CI+IP+gT/5kHVv/jVAHpNFebf8Ij4g/wCgT/5kHVv/AI1R/wAIj4g/6BP/AJkHVv8A41QB6TRXm3/CI+IP+gT/AOZB1b/41R/wiPiD/oE/+ZB1b/41QB6TRXm3/CI+IP8AoE/+ZB1b/wCNUf8ACI+IP+gT/wCZB1b/AONUAek0V5t/wiPiD/oE/wDmQdW/+NUf8Ij4g/6BP/mQdW/+NUAek0V5t/wiPiD/AKBP/mQdW/8AjVH/AAiPiD/oE/8AmQdW/wDjVAHpNFebf8Ij4g/6BP8A5kHVv/jVH/CI+IP+gT/5kHVv/jVAHpNFebf8Ij4g/wCgT/5kHVv/AI1R/wAIj4g/6BP/AJkHVv8A41QB6TRXm3/CI+IP+gT/AOZB1b/41R/wiPiD/oE/+ZB1b/41QB6TRXm3/CI+IP8AoE/+ZB1b/wCNUf8ACI+IP+gT/wCZB1b/AONUAek0VieGNFbSLBnuVuIruf8A10Ums3WoxptJ27HnwRkHJwq88c4BrboAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKAIrq5js7Oa5myI4Y2kfAycAZP8q5T4ZXE+seC4PEWo832uFruU/3ELERRr6KqbQPfcerGuo1GyTUdLurGbiO5heFuM8MpB4/GuW+FKzWvw60/Sb4FL7R92n3UTdUaNiB+DJtYeqsKAM/4eRCDxz4/hV5XSPU4QvmytIQDbocZYk9SauSam+hfGC00hWP2HxBYSzrFjhLmEjcw9NyNz7oD1JzU8B22u23jXxXeav4bvdNtNYuo7m2mmuLZ8BIljKsI5WIY4yMAj3HexqFjLrPxr0e4i3fZvD2m3EkzgfL5tyVRY8+u2MsR2G3+8MgHcUUUUAFFFFABWP4tbHhS/RrWW6SaLyXSGBp2VX+Uv5a/M+0EttXk4wK2KKTV1Yadnc8x0axgsz4dnfR7t501diNQayu5JpVa2ZDLJ5ytLCCxRMO2MKMHaOJfGFxbeJL7TZbTT729gWF/LUWd4sd+GYq0DyxYEa5jXImBRtwOMDNek0VT1ZK0/rzucfqMeln4haOF0i8j1KJS51KLT5WjSPYyi3M4QqFO4ttJCgrn7xGewoopdBhRRRQAVwni641Fvi78PbG1Ej2O/Ubu6VI9wUpbeWjs2MqAZyvUAlx1OK7uuH17xFpml/FSyF5O6tp3hy+vLpY4JJDHC9xahWwqknmKTgZI25OBik2krsN9EWfifBHd+AdRgeNZJFhe5jyoYoYVMu4D1yoGR0LCmi4bxR42sYztfStPt/twjKgiWVjthkPqPlkZf8AdDc5XGfZ+Pfh74ruBq2n2k+tTW6tbi9g8OXdw0YYfNHvEBwCG5XPQ+9Wk8TeC9GurzWY9Ev7C4lQtd3y+FbyJ3UckvJ5AJHGeT2prR3f9f1oD1Vl/X9anb1FdSxQWc0tzjyY42aTIz8oHPH0qppeu6frWgQ61pczXNhcRedFIkT5dfZCN2eOmM1x6/Ev4feNLa505BceIIYiv2i1GgXd0qHPG9PJIHI4yOopPrHqNd+hBomiWUjL4L1qxtbiOwuk1O3tpoVZYYHBYBRjACzF4x/sDFej1yy+NdBhYOmna5GVQIGHhm/GEHQZ8joPStTw54n0jxbpP9p+H7o3Vp5jReYYnjO5Tgja4B4+lVv/AF8v8ifX+uv+Zq0UVDdyTxWkj2kH2icL+7iLhAzdst2HqcHjselIZNRWN4c1u41iO+i1GxWwv9PujbXMMc3nR52K6sjlVLKUdTyoIJIxxmtmgAooooAKKKKACiiigCvfyxw6fO80YlQIQYzj95ngLz6njHvXmelyXEXgey8JaVIYWOqT6XLKi42RrcSFkT+6fJRmz2G3puBGre/EX4e+IdSn8PXyyaxd2khaXT30G6uWiZDgsU8k4wT1x396sza14Nub+3vrjw3qEt3asXguJPCV60kTE7iVY2+VJJJyO/NJWdn0/r/gje1uv9f8A7K3t4bS2jt7WJIYIkCRxxqFVFAwAAOgA7VJWJ4c8X6L4r+2DQ7qSZrGXyblJbWWB4nxnaVkVTn8Kxda+JPglNcuPCWsTzXN/IDHLph0m5uDMpXJG1YiHUrzxkEU29fNiWxlw6fZPf6h4evLW3k0zxQ41C1tHiUx8Sfv8LjH3BFJ/vuxr0aGGK3gjht40iijUIkaKFVFAwAAOgA7Vytr4r8N2UFvDZaPrFvFbJsgji8L3yLEvooEHyjjoKvaH430LxFrF3pWmXFx9vs41kuLa5sZ7Z41boSJUXrQtrL+rf5IXm/6v/mzfooprsUjZlQuQCQq4y3sM8UDHUVhaHr19favqGlaxpken3tmkU4EFz58csUm4KwYohDZjcFcYGBgnNbtABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFQi0gW8a7VNs7IEZgSNwByMjocc4J6ZOOpqaigAqG1tILONktowgdy7nOS7HqSTyT7mpqKACiiigAooooAKKKKACiiigAooooAKKKKACuWs7aB/i9rNy0MbXEehWEaSlBvVWnvCyg9QCUUkd9o9BXU1zfh3/AEjxf4tupvmmhvbewjbpiBLWKZUx04kuZmz1+fGcAAAHm3jDwTrPwz8SzePvhjB5lm/zaxoS5CTJnJdAOmOTxypyRkErXp3gvxlpfjvwxBreiuxhk+SSNxh4ZB95G9xn8eDUXiTVL2e7j8O+HZRHql0m+e5xuFhb5wZSOhc4Kop6nJ5CtWromi2Ph7RbbStJhENpbLtRc5J7lie7Ekkk8kkmiOkWnt0/X5fqEtZX69f0+f6EmmabbaPpsVjYp5dvDkIn90Ek4/WvLviJ8NtUsfEA8f8AwxZbXxDBlryyA/d6inVgV7sccj+Lg5DAE+tJIkmfLdW2kqdpzgjqKxfEut3GnRQ2Gjxx3GtX5KWcMmdi4+9NJjpGgIJ9SVUcsKl33jv0Guz2Mv4b/EXT/iJoD3drE9nf2rCK+sZPvW8np2yDg4Psc4IrpbDTbbTftItE2C5uHuJB6u33j+JGaqeG/D1t4b0s2sDtPPNK1xd3UgAe6nbl5Gx3J7dAAAOAK1FkRnZFdSyY3KDyv1rSVr3X9d/lclXtZmDrPjC00rW4NFtrK91bVpoTOLKxVC6RA43u0joijPAywyemai0zxjF4m0/UB4Yt5G1KyZoXg1GCW3ijnU4aNpQjKSp67C3bsQa47xW5PxBOs6HBryW62hsdQ1Xw5HFcuzhz+6eKRW+5ySyKzAnacYrY0O90zRPDGiDwIsVzpl5qnk3k928vnl3ZhIzBgGMu8c78Y9OgqY2kvXT73ZfL+thy91+n+V38/wCtza0qfUtB8N39/wCLIrGA26PczvZ3DT+ZtUs7lmjjx0wFwcBRye0HhSSRvDK+LNZSaW/1C1F1JHEjymCIjesMSDJ4GMhRlmyeeK0/F2lS654L1nSrcgTXtjNBHk4+ZkIH6msfwv4ijt/hn4dvF0+/ut0EFpJDawGSSFwPLbevUBWUhj2oTvf5W+d/+AD0S+d/w/4IumfErSNZi01tLsdWunvrlrd4o7Ji1ltcoz3HaJcr3Ofbg46+uD8G2d9ofjjxPZ3OmTJDqdzHqcd0kX7oF48SJ5nQlWQDHX584xnG63ipU8JXGupp17fLDJIgtdOgkknk2SmP5UdUbdxkjGBzgsMEjatf+v6TCzvb+v6sbssghheRwxVFLEIhYkD0A5J9hzXKWfxF0u/8LarrtpY6rJDpNy1vc232MrcBl27j5RIIADA84OAeK6TTb+HVdKtdQthIIbqFZkEiFWAYZAIPIPPSuE8LaXdN418bWU1s6abNq8dy0rLhZs28RMY45BOC3UY4/ioXxNPt+qDSyfn+jPRAcgEdDXHLc/8ACK/ECx0hHkbTNfSZ4I3csLa5jAZlTJ4R0LHb0BTjG410T6oi+IYtKVcyNbPcMSrjADKowduw9Tn5gRxwQcjlvFFq2q/FTwdb2/zHTRdahckfwRmPykz/ALzPx/ut6ULdP+vP7t/kHR3/AK7ff+pmfE/4XS+JLmDxP4PuBpXi7T8Pb3SHaLgD+B/fHAJ7fKcg8Wvhf8Tf+E1judI1uzbS/E+l/Lf2TqQDg4Mi57Z7dsjqME9b4g1yPQtOEwha6u53ENnaIcPczH7qD06EluiqCx4Bqr4X8Oto8dzfalJHda3qTLLqF0i4DMBhY07iNBwo+pPJNENLrp+vl+vyCWtu/wCn9bGnb6bbWuo3l9Am2e92GY/3ig2g/lx+Fch8TfhlZfEDS45YZf7P16x+fT9SjyrRsDkKxHO3PPqDyO4PceYnmeXvXfjdtzzj1xVTV9WtND0qbUNQcrDEBwqlmdicKiqOWZiQABySQKTV0NXuedfDP4k6jeaxJ4H8f2xsvFdipw+PkvkA++uOM4544PUY5A9H/s22/tn+1AmLo2/2cv6pu3Afnn86xPDWh3P9oT+JfEUSDW72MRLEpDCxt85WBT3OeXb+JvYLjpDIiyKjOods7VJ5OOuKp9G9/wCv0/4BKtqlt/X6mX4j8S6f4X06O71NpGM0y29vBBGXluJW+6iKOpP5etZtp46trnWv7Dn0vUtP1tofPisru33gocgO0sHmxohYEZZsg9umcj4oRjULfTrbTLO6vtZsrqO9j/s6RPtVlGNwMyq+EbOCoVyA2TjO3FN8Gf2Tc3+r3ulXOpXHiyWCNbpvEdu0NxDHk7F8tURRGDuOIwAxHLZ5Cjrf+unT538vmOWlv669flt1+R0HhqDxHHcXU3ia10uKSY58yyu3mL8/KuGiTYqjt82SxPHejot2PFvijVbyYsdP0O9NjZw7iFedFBllYdGIZtq56bSep40/DOo6peJqNrrqW5u9PvDbm4tY2jiuF2I6uqMzFeHCkbm5U89hzvgBW0Gbxnps8Mslxa6xPfrHGuWlinUSRlR3Jwy/VSKE7O/S1/y/Rh0+f+f62L9x8StGt77WLE2uqve6UqE2i2EnnXe4sB5CEZk5Q842984yR1Nnc/bLGC58maDzo1k8qddskeRnaw7MM4I9a8/vXvZfiF4b8X22h6g1vdWc2nyQtakTwBgsqNIp/wBX86lOeBnk88dhLryx6hqtsttLOdNtY7ho4I3aWTcHO1QVCsTswNrkk5BC4GTaOu/9fpZhu9P6/pmtXNab4607VrrXbWys9SNzoaq08Elm0ckoZWZfLRsM2dpAyBnjHrWn4e1yHxHocGp29reWazbg1vewmKaJlYqyuh6EEGuPXT74/GnXUt4ZUtdQ0e0E10owI9skoIB/vFRgc8de1DTvy+v+Y1a1/wCt7HcaXqEWraRaajbpLHFdwJMiTJtdQyggMOx55Fcz44uD4ViXxhatKq2rxR6jArny57ZnCsxXON6btwYc4BU8Hjf1LUIdFs7RUjUCW4htYUCvtG5guPkRtuBnGQFzgErnI5z4txNe/Da/0q3G671V4rG2Tu8kkij9Blj7KTQ97x7/ANL8fxFFdJf15naAhgCOQelFMgi8m3jiByEULn6Cn03uJXtqFFFFIYUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFAHm2nz32iftDX9lqF15tt4i0VbiCSYMiiW3mdVt4MsR8sUhd1GSWLPhQ22tbTrrUILPxpq+gaf/ak9xqrmwg81YvtDw28Fs4JYjaBNBKpJxkJkZBBOB8Z3/sK/wDBfjRZriBdE1pYbuaOLzI4bO4G2d3UKT0VVBHd8D5iuOu8B/8AIu3X/Ya1X/04XFJq6sNaM8l0i++PujrcmHwPok9xdzGe5uZ7iMyTMeBki5AwFAUAAAAAVfk8TftDvEyr4I0GMkYDrPHlfcZuSPzFekX3iY6Vfa/dXg36fpkNuMC7hjG9txYZl8tUOGT70hBBXABznmr/AOIVr4s8N6nFoVxcafcWaR3Blt9SsZmZRIoK/uJpWUHOCcLxxmmtdEJ6anReBLTXdI+HVqPEcMk+u7Zri6iEqFnmeR32hgdgzkDrgfSvLre/+PNprmo6pB4F0aSe9cAPc3cbvFEv3IVIuFG0ZJ6DJJJ6173WTr9/cWa6fFZjMt3fRQcShGC8u5GUYH5UbI44zhgcGh6yv/WobRt8zyc+KP2hiD/xQvh8e/np/wDJVdz8LrPxXB4evbrx/GItavr555I1kRlRNiIgXYSoGF6Z9zyTUFj8VtG1XWotHt42iuLiXyEkXVdMcqxOMhFuWc/QIT7VueBpJ5PBlibu6nvJl8xWnuG3SSYkYZY+vFNPS/cT3sVofA40+e4Oh+ItY0m2uZ3uJLO3aCSLzHJZyvmxOy5JJwrAZPAFSX3hJxpunWWgXcNhHZ3wvZDcwPctO24u2W8xTuZiSWJPXpXS0Ulpby/Qb1v5hWfZ6Laafql5fWXmQtekPcQq58p5OnmbTwrEDBIxnvkgGtCigBsodoXWJwjlSFYrkKexx3rO0nRl0/w3aaTPO1x5EKxyTIWjMpHVuGyMnkjPetOigDO1PRxqNhBa299eaYkEscitYOsZIQ5CHII2HoRjkcVdggjtoFihXai5wM5JPUkk8kk8knkk1JRQBgeH3l1PU77XJrS5tEnSK3t4rqMxyBEBZiyHlTvdh7hQRwQToabo1rpk1zcReZLdXb7p7mZt0kmM7Vz2VckBRgDJ4yTm/RQB4bq198bD45vNY0nwNpk0Cg29gL67idoIc8kbZ1AZ8AscZ4AzgVL/AMJR+0N/0Inh/wD7/p/8lV6h4g1iXS9R01Y+Ym8+e5AnjjPlRxEnO9cEbiozvjwSpJxkVy6/EzTfFdpfaVpMk1jdyWczR3MGqadM8ZVCcqsVxI2eOuw49utRflj6Iq15eo74XwePJr/W9W+JVpHZ3dz5MVpBDLG0aRJvJ2hGbHL9Scn6AVz3ji5+Lc/j5Lrwx4NsL3SdNyLH7fdREPIRgz7RMhDYJVc9AT0JNeqaBI83hvTJZnaSR7SJndjksSgySe5qLxNfz6b4curizG65IWKECQRne7BFwxRwDlhjKkZxnitZq0/QiDvG/c8n/wCEo/aG/wChE8P/APf9P/kqtz4er8TdT8cXGq/EnTbfTbSCxaGzgtJYzHvd0LHCyOxOEHLHjt1NbviL4n6R4Y1mTS76HfNGqszf2np8OcjP3ZrlHH4qParnhi7mu/EmuSteXFxbzJaXEEUsiOsCvGTtTZ8uOM5BOTzk8UovqgfYsan4RivtdOtWGq6jo+ovAtvLPYtGRNGpJVWSVHQ4LNg7QeTzT4fDktjbXs1hqckmtXcSxHU9QjEzALnaPLTy1AG5jtUKMnJzW7RS6WKvrcx/Del6ppOnm31jUrfUJAfleC0aAdyzMGkkLMSSScgdMAd7F3otpd6va6ofMhvbUFFmhcqXjPJjcdGU9cEHB5GDzWhRR1uLpYKzLDSHtb3Vri5uvPOozB12KYzEgjVAgIY+hORjljWnRQBn3+jx3mhT6XbXV1pqSoVFxYyBJo8nJZWIPzE55IPU1ZtLVLOHYhZ2J3PJIctI395j68D2AAAwABU9FAHP3Ly6r4ttLUWlzHbaVI1xLPLGUjlcx7YwjdHH7x846FBnqM6L6Naza3Hqlx5k9xCm23WRspb5GGZF6BiDgscnHAIBIq/RQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAcl8VNB/4SX4U+ItMWO4lleyeaGK2XdJJLFiWNAMHOXRRgDJBwMHmpPhlAkHwt8OMpkd7nT4rueSWRpHkmmXzZXZmJJLO7MfrXU0UAVbPTbWwmu5rWNke8m8+cmRm3PtC55JxwoGBgcVFrWi2XiDS5NO1NZntpCC6w3EkDHByPmjZWx7Zq/RQA2OMRRJGpYqihQWYscD1J5J9zWSdP1C68ULeXzW4sLIMbNIixd3dVUtICMAr84GCch+cY52KKOtwGugkjZG3AMCDtYqfwI5H1FUtF0Sy8P6YthpazLbozMqzXMk7Ak5PzSMzde2av0UAFFFFABRRRQAUUUUAFFFFABRRRQBVfTbWTVotTeNjdwwtAj+Y2AjEFhtzjkqvOM8U6/sYNT0+eyu/MMFwhjkEUrRMVPXDKQw+oIqxRRurMNncradp9vpWmwWFkJBb26COMSyvKwUdAWclj+JNUNS0/UNR1uzV2t10m3dLlsFvOklXdhSMbdmSjZzkFMY5yNiijd3FbSwVnWehWNjrN7qtuLgXd8FE5e7ldG29MIzFVx/sgVo0UDCiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigAooooAKKKKACiiigD/2Q==\"\u003e\u003c/div\u003e\n \u003c/div\u003e\n \u003cp\u003ewhere \u003cem\u003eM\u003c/em\u003e and \u003cem\u003eN\u003c/em\u003e are the number of sampling data along \u003cem\u003ex\u003c/em\u003e-direction and \u003cem\u003ey\u003c/em\u003e-direction respectively. Figure \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ea shows the curve giving the variation of the correlation factor as a function of continuation heights. It is an increasing curve which presented a maximum deflection noted C at a certain continuation heights. This deflection is given by the gap between the curve of the correlation factor and the line joining the two ends of the curve. In Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003eb, we plot the curve giving the variation of the deflection C at each altitude as a function of continuation heights. This curve passes through a maximum altitude Hm\u0026thinsp;=\u0026thinsp;25km called optimum altitude of upward continuation of the Bouguer and also corresponds to the depth of investigation in the region. For the choice of the regional degree, we calculated the coefficients of correlation between the upward continuation of the Bouguer map at 25km and the regional anomaly maps for different degrees (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ec). We find that the upward continuation of the Bouguer map at optimal altitude present a maximum correlation with the regional anomaly map of order 4. Thus, residual anomaly map of degree 4 will essentially highlight the gravity effect of shallow structures in the study area.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv class=\"Section3\" id=\"Sec9\"\u003e\n \u003ch2\u003e3.2.2. Power Spectrum Analysis\u003c/h2\u003e\n \u003cp\u003eThe Spectral analysis is a method that permits to define the planes of separation between several structures of different densities. When we plot the logarithm of gravity energy as function of frequency, the spectral curve has two slopes. The first slope located in the low frequencies corresponds to the deep structures. The second slope located in the high frequencies corresponds to the near surface structures. The average depths of gravity anomalies sources can be estimated from the relationship (Gerard and Griveau 1972; Dimitriadis et al. \u003cspan class=\"CitationRef\"\u003e1987\u003c/span\u003e):\u003c/p\u003e\n \u003cdiv class=\"Equation\" id=\"Equ2\"\u003e\n \u003cdiv class=\"EquationNumber\"\u003e\u003cimg src=\"data:image/jpeg;base64,/9j/4AAQSkZJRgABAQEAYABgAAD/4RD6RXhpZgAATU0AKgAAAAgABAE7AAIAAAAQAAAISodpAAQAAAABAAAIWpydAAEAAAAgAAAQ0uocAAcAAAgMAAAAPgAAAAAc6gAAAAgAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFNhY2hpbiBNYWhhcm51cgAABZADAAIAAAAUAAAQqJAEAAIAAAAUAAAQvJKRAAIAAAADOTUAAJKSAAIAAAADOTUAAOocAAcAAAgMAAAInAAAAAAc6gAAAAgAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAADIwMjI6MDY6MDIgMTQ6MTA6NTgAMjAyMjowNjowMiAxNDoxMDo1OAAAAFMAYQBjAGgAaQBuACAATQBhAGgAYQByAG4AdQByAAAA/+ELImh0dHA6Ly9ucy5hZG9iZS5jb20veGFwLzEuMC8APD94cGFja2V0IGJlZ2luPSfvu78nIGlkPSdXNU0wTXBDZWhpSHpyZVN6TlRjemtjOWQnPz4NCjx4OnhtcG1ldGEgeG1sbnM6eD0iYWRvYmU6bnM6bWV0YS8iPjxyZGY6UkRGIHhtbG5zOnJkZj0iaHR0cDovL3d3dy53My5vcmcvMTk5OS8wMi8yMi1yZGYtc3ludGF4LW5zIyI+PHJkZjpEZXNjcmlwdGlvbiByZGY6YWJvdXQ9InV1aWQ6ZmFmNWJkZDUtYmEzZC0xMWRhLWFkMzEtZDMzZDc1MTgyZjFiIiB4bWxuczpkYz0iaHR0cDovL3B1cmwub3JnL2RjL2VsZW1lbnRzLzEuMS8iLz48cmRmOkRlc2NyaXB0aW9uIHJkZjphYm91dD0idXVpZDpmYWY1YmRkNS1iYTNkLTExZGEtYWQzMS1kMzNkNzUxODJmMWIiIHhtbG5zOnhtcD0iaHR0cDovL25zLmFkb2JlLmNvbS94YXAvMS4wLyI+PHhtcDpDcmVhdGVEYXRlPjIwMjItMDYtMDJUMTQ6MTA6NTguOTUwPC94bXA6Q3JlYXRlRGF0ZT48L3JkZjpEZXNjcmlwdGlvbj48cmRmOkRlc2NyaXB0aW9uIHJkZjphYm91dD0idXVpZDpmYWY1YmRkNS1iYTNkLTExZGEtYWQzMS1kMzNkNzUxODJmMWIiIHhtbG5zOmRjPSJodHRwOi8vcHVybC5vcmcvZGMvZWxlbWVudHMvMS4xLyI+PGRjOmNyZWF0b3I+PHJkZjpTZXEgeG1sbnM6cmRmPSJodHRwOi8vd3d3LnczLm9yZy8xOTk5LzAyLzIyLXJkZi1zeW50YXgtbnMjIj48cmRmOmxpPlNhY2hpbiBNYWhhcm51cjwvcmRmOmxpPjwvcmRmOlNlcT4NCgkJCTwvZGM6Y3JlYXRvcj48L3JkZjpEZXNjcmlwdGlvbj48L3JkZjpSREY+PC94OnhtcG1ldGE+DQogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIAogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIAogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIAogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIAogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIAogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIAogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgIDw/eHBhY2tldCBlbmQ9J3cnPz7/2wBDAAcFBQYFBAcGBQYIBwcIChELCgkJChUPEAwRGBUaGRgVGBcbHichGx0lHRcYIi4iJSgpKywrGiAvMy8qMicqKyr/2wBDAQcICAoJChQLCxQqHBgcKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKir/wAARCAA5AcwDASIAAhEBAxEB/8QAHwAAAQUBAQEBAQEAAAAAAAAAAAECAwQFBgcICQoL/8QAtRAAAgEDAwIEAwUFBAQAAAF9AQIDAAQRBRIhMUEGE1FhByJxFDKBkaEII0KxwRVS0fAkM2JyggkKFhcYGRolJicoKSo0NTY3ODk6Q0RFRkdISUpTVFVWV1hZWmNkZWZnaGlqc3R1dnd4eXqDhIWGh4iJipKTlJWWl5iZmqKjpKWmp6ipqrKztLW2t7i5usLDxMXGx8jJytLT1NXW19jZ2uHi4+Tl5ufo6erx8vP09fb3+Pn6/8QAHwEAAwEBAQEBAQEBAQAAAAAAAAECAwQFBgcICQoL/8QAtREAAgECBAQDBAcFBAQAAQJ3AAECAxEEBSExBhJBUQdhcRMiMoEIFEKRobHBCSMzUvAVYnLRChYkNOEl8RcYGRomJygpKjU2Nzg5OkNERUZHSElKU1RVVldYWVpjZGVmZ2hpanN0dXZ3eHl6goOEhYaHiImKkpOUlZaXmJmaoqOkpaanqKmqsrO0tba3uLm6wsPExcbHyMnK0tPU1dbX2Nna4uPk5ebn6Onq8vP09fb3+Pn6/9oADAMBAAIRAxEAPwD6RooooAKKKKACsbxZq9xovhu6udOg+06i6+VY24xmaduEXkjjPJ9ACe1bNcLqPi3wz/wsFodc8QaTYLoSDy4bu9iiZriVeXwxB+WM4B7+a3pSavoNaam54I8Sp4u8FabrSrskuYR58f8AzzlX5ZF/BgRVSTU21n4ivoKH/Q9JtEu7tf8AnrNIxESn2AR2I7kp6Vx/gDxBo2n/ABZ8Q+HNF1ex1DTdY/4nFibO6SZY5TxPHlWOCSA4HpmtvwgJE+L/AI/Wf7zGweM7v+WfkkDj6hv1q73altpf9LfJ/kTsmu39fivzND4oapqGi/D2/v8ARdQmsNRiKLatDHG5lldgiRlZFYEFmHQA+4rb8PWGpado8UOtavNq16QGluJYoo/mwMhVjRQFznGcnnrXn3xD8XeHrnx94X8NX2t6bBBa3x1HUmuLpFWHyUJijYk4DM7A4POBW3q/jy11vTNc0/wBdw6zqVrpU1wJrGUSpFIQREoZchnY5IAORt56jOfNaDl/Vkv+H+4q15Jf1q/+G+82Lzx54bsb6S1uNS+aGYQTzRwSSQW8hIASWZVMcbZI4dgeRUuq+MtE0fUv7Pu7maS9Efmvb2lpNcyRx/33WJWKL7tgV5rcDS9Z+Fem/D/wFKmoT3yRQ30sR3fYk3Bp5Zz/AASE7vlbDFj04pt/qFr4e+IniOKy8UJ4cg1XyUmv9S09p0eZY9pENxuWNNo4IkJw2cLiras7ev8AX/B17CTTV1/X9dj0DVPFekah4G1fVtB8R27RWVs8r3unTRTmEqu/GCGXOB0I71yumWvjO/8AB1ksnjnUovFV3pf24W/2OxMEbcYVl8jcASwX73UMe2KzPHd54W8M+AfD/wAPrHWbNLbUJ7aGR7m7QlbPf5kkztkABtpGeAS3HTje0PU/h3pPjOKDwNJo02oaxGlubXRTHsRIy7vK5jyq4Vu+CSAPorJydtr2+5f8FfcxXaSvvv8Ae1/kzc8WXr+F4tO18y5SK5gtNSY8LLDIwj3kDgFXZWB7DcO9dXXCfGvcfg7ryxnEjRxqnOPmMqAfrXb24dbaISnLhAGPvjmhap+v9f15j2t/W3/D/gSUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAV554iFhefGbRHmtIpZdFsJLppEiDTPJKTHDEDjOMCZsZwMbjgDNeh15rpdhf2V9448d3Gn3suozNJb6dZCBt5ht1KoVTGSZGBIOOQRjrzLdnftd/p9+o7XVu9l/XyO08N+IrXxPpJv7OGeAJPLbyQzhd8ckblGU7WZTyDyCRVSX4g+DLeZ4Z/F2hRSxsVdH1OEMrA4IILcGovhzojeHfh7pOnSpIs6Q77gyLhnlclnYg8jLEnnB9QDxUstl4zaZzBr+hJEWOxX0OZmVc8AkXYyffA+lXJWdiU7q5o6Tr+j6/FJLoWrWOpxxNtkezuUmCH0JUnBrQrP0mHWIYpBrt/Y3khb921nZPbBR6ENLJk++RWX/wi+r/9D34g/wC/Gn//ACLSGdJXPXely2PjaLxBaRtLHc2osb6NBlgFctFKB32lnUjrhwf4aZ/wi+r/APQ9+IP+/Gn/APyLR/wi+r/9D34g/wC/Gn//ACLR1uHSx0lFc3/wi+r/APQ9+IP+/Gn/APyLR/wi+r/9D34g/wC/Gn//ACLQB0UieZGyEkBgRlTgj6Vx2keEPEGiaLDoVl4js20iCPyIxPpO+5WLpjzPNEZIHcxH3Bq//wAIvq//AEPfiD/vxp//AMi0xfDepu7onj7XmZCA6iHTyVyM8/6LxxSsO5s6LpFpoGh2Wk6cpW1soVhiDHJ2qMc+9Xq5v/hF9X/6HvxB/wB+NP8A/kWmDw5qbStEvj/XjIgBZBDp+VBzgkfZe+D+VU227sRN4k0qTxFdafprIy2MF1Fe3jsvEgjbdHGPUlwpPoFIP3hXQ1zf/CL6v/0PfiD/AL8af/8AItdBbRPBaxRSzyXLxoFaaUKHkIGCzbQFyepwAPQCl0sBJRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQByPiLWXufHGi+EbaQoLuGW+vmU4b7PHgBAQcje7AE/3VYd8h/iDwdc69JKW8R6ro9vDGEs4tKufs6xYHLvgfOc8bSduFHGSazNVtZNP+Peg6vIcW2o6PcaWpPQSq4nC+gJUMR3Ow0eMvFe3V20CXRPEM+nbAb25sNInmWcH/lijquMEfeYHodo5JKgFXQb/AF/WPghY+IbyVf8AhI7WyluYLgKAJ9hYpuA6pKipuH+1kYIGO28Oa3B4k8M6drVoMQ39sk6rnJXcoJU+4PH4VkTeI4ZPh1qmstpt1plpb2k5jt763MMhREIGYjgrkggDuMHvT/hvpFzoPwz8P6ZfrsubexjEqf3GIyV+ozj8KAOmooooAKKKKACiiigDmvHXiG70Dw3dvo8KT6q1tLJbRuflQIu5pH/2V4+pKjvUvhHWZLz4caNrWt3cYkl0yG6u7mTbGoJjDO5xhVHU9gKwfGWieIotJ8Uajba1pn2e5sZR5VxpckkscSxH92sguFUc7jnZ1bnOBVLwxq58P/A/QJ9fjh1dp7O1i0+ytbNg0zmNTFEQWcM2Rkv8o4zgYpR2l8vxvp/X+Q2tV8/0/r+mSSfH/wCGUcjI3idSVJBK2Vww49CI8H6ipdS+J8MfiXwyNLjNxoGqMkd1fshQRPOpNsMMAwLbSTkcBlJ6jOTd+IbLwz44sNP8RPLJLpOlS6tOYYGZJLmZm82XcflRUUSAbiOJNoycCotT1DwX4h+GeqaZqHjHw9FqusBryWQarD+6uuGjAO4cR7Y0B7hOepoukubt/m0/ydvl3C13b+tr3/Ff0j0Hxp4gPhbwVqutLH5slnbs8UZ/jfog/FiKsaFZHR/DltDcO806Qh7mbaWeaUjLuQOpLZOB9BXlmu+JH8d/swy6ujq91DHCb5VO4eZDMhl6E8YUt9CK9W1nWINF8M32sTEGGztXuTg9QqlsD64py9xSf9f0/wBBR97lX9dPy/UzP+E/8ODRJtWe8njtbeSSOXzLGdZIzHjfmIpvAXIy23A7mqnjvUV0TS7DxVauNtjdQid0GfNtZXVJFPqBuVx7oK4LUNFn0X4NaXod9Oy6v4su4YLuQL8yLM5mmQDqcKZB3JLH1rrvjHbj/hTWr2VsuDIkFvAgB5ZpUVVH4kU2mn5ppfPS/wCf5hGzaXR/l0/X8DvutFR26NFbRRudzKgUn1IFSUPcSd1dhRRRSGFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAVr6wt9StvJu03KHV0I4ZHU5VlPYg8g1YRSsaqzFyAAWbGW9zjilooAqX2mwaiYReBpIoZBL5JPyO6kFSw77SMgdM4PUDFuiigAooooAKKKKACiiigAooooAKKKKAIL6yg1LT7ixvYxLb3MTQyoejIwwR+Rqn4ftbzTtHh06/bzms1EEdzuyZ0UYVyOzYxn3zjitOijYArF1nSH1zUdPiuV2afY3CXj8j9/KnMa4/uq2HOe6qBnnG1RR1uAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAFFFFABRRRQAUUUUAf/Z\"\u003e\u003c/div\u003e\n \u003c/div\u003e\n \u003cp\u003ewhere \u003cimg src=\"data:image/jpeg;base64,/9j/4AAQSkZJRgABAQEAYABgAAD/4RD6RXhpZgAATU0AKgAAAAgABAE7AAIAAAAQAAAISodpAAQAAAABAAAIWpydAAEAAAAgAAAQ0uocAAcAAAgMAAAAPgAAAAAc6gAAAAgAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAFNhY2hpbiBNYWhhcm51cgAABZADAAIAAAAUAAAQqJAEAAIAAAAUAAAQvJKRAAIAAAADMTIAAJKSAAIAAAADMTIAAOocAAcAAAgMAAAInAAAAAAc6gAAAAgAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAADIwMjI6MDY6MDIgMTQ6MTE6MTkAMjAyMjowNjowMiAxNDoxMToxOQAAAFMAYQBjAGgAaQBuACAATQBhAGgAYQByAG4AdQByAAAA/+ELImh0dHA6Ly9ucy5hZG9iZS5jb20veGFwLzEuMC8APD94cGFja2V0IGJlZ2luPSfvu78nIGlkPSdXNU0wTXBDZWhpSHpyZVN6TlRjemtjOWQnPz4NCjx4OnhtcG1ldGEgeG1sbnM6eD0iYWRvYmU6bnM6bWV0YS8iPjxyZGY6UkRGIHhtbG5zOnJkZj0iaHR0cDovL3d3dy53My5vcmcvMTk5OS8wMi8yMi1yZGYtc3ludGF4LW5zIyI+PHJkZjpEZXNjcmlwdGlvbiByZGY6YWJvdXQ9InV1aWQ6ZmFmNWJkZDUtYmEzZC0xMWRhLWFkMzEtZDMzZDc1MTgyZjFiIiB4bWxuczpkYz0iaHR0cDovL3B1cmwub3JnL2RjL2VsZW1lbnRzLzEuMS8iLz48cmRmOkRlc2NyaXB0aW9uIHJkZjphYm91dD0idXVpZDpmYWY1YmRkNS1iYTNkLTExZGEtYWQzMS1kMzNkNzUxODJmMWIiIHhtbG5zOnhtcD0iaHR0cDovL25zLmFkb2JlLmNvbS94YXAvMS4wLyI+PHhtcDpDcmVhdGVEYXRlPjIwMjItMDYtMDJUMTQ6MTE6MTkuMTE4PC94bXA6Q3JlYXRlRGF0ZT48L3JkZjpEZXNjcmlwdGlvbj48cmRmOkRlc2NyaXB0aW9uIHJkZjphYm91dD0idXVpZDpmYWY1YmRkNS1iYTNkLTExZGEtYWQzMS1kMzNkNzUxODJmMWIiIHhtbG5zOmRjPSJodHRwOi8vcHVybC5vcmcvZGMvZWxlbWVudHMvMS4xLyI+PGRjOmNyZWF0b3I+PHJkZjpTZXEgeG1sbnM6cmRmPSJodHRwOi8vd3d3LnczLm9yZy8xOTk5LzAyLzIyLXJkZi1zeW50YXgtbnMjIj48cmRmOmxpPlNhY2hpbiBNYWhhcm51cjwvcmRmOmxpPjwvcmRmOlNlcT4NCgkJCTwvZGM6Y3JlYXRvcj48L3JkZjpEZXNjcmlwdGlvbj48L3JkZjpSREY+PC94OnhtcG1ldGE+DQogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIAogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIAogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIAogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIAogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIAogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIAogICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgCiAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAKICAgICAgICAgICAgICAgICAgICAgICAgICAgIDw/eHBhY2tldCBlbmQ9J3cnPz7/2wBDAAcFBQYFBAcGBQYIBwcIChELCgkJChUPEAwRGBUaGRgVGBcbHichGx0lHRcYIi4iJSgpKywrGiAvMy8qMicqKyr/2wBDAQcICAoJChQLCxQqHBgcKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKioqKir/wAARCAAlAFUDASIAAhEBAxEB/8QAHwAAAQUBAQEBAQEAAAAAAAAAAAECAwQFBgcICQoL/8QAtRAAAgEDAwIEAwUFBAQAAAF9AQIDAAQRBRIhMUEGE1FhByJxFDKBkaEII0KxwRVS0fAkM2JyggkKFhcYGRolJicoKSo0NTY3ODk6Q0RFRkdISUpTVFVWV1hZWmNkZWZnaGlqc3R1dnd4eXqDhIWGh4iJipKTlJWWl5iZmqKjpKWmp6ipqrKztLW2t7i5usLDxMXGx8jJytLT1NXW19jZ2uHi4+Tl5ufo6erx8vP09fb3+Pn6/8QAHwEAAwEBAQEBAQEBAQAAAAAAAAECAwQFBgcICQoL/8QAtREAAgECBAQDBAcFBAQAAQJ3AAECAxEEBSExBhJBUQdhcRMiMoEIFEKRobHBCSMzUvAVYnLRChYkNOEl8RcYGRomJygpKjU2Nzg5OkNERUZHSElKU1RVVldYWVpjZGVmZ2hpanN0dXZ3eHl6goOEhYaHiImKkpOUlZaXmJmaoqOkpaanqKmqsrO0tba3uLm6wsPExcbHyMnK0tPU1dbX2Nna4uPk5ebn6Onq8vP09fb3+Pn6/9oADAMBAAIRAxEAPwD6RooJCqSxwBySe1edeFvGuo33xJvNP1QImlaxaC+8PsD9+KM7HyfVhtkA5wrfgBauwbK56BdXMFlaS3N3KsMEKF5JHOAqgZJJpbeb7RbpKI3jDjIWRcMB2yO306+tcd46vDP4k8I+HQcR6pqLTXC4zvit0Mu0+xcR5/LvXa0dL/1/X+QPe39f1oFFebfDPTW1DV9e8RNq+sXVl/ak1tplvcarcSwpFH8jNsZyGy+/G7OABjFdTqfjC0stYfSNPsr3WdUiiE01pp6oWgQ9C7yOiKT2UtuPUA0aWT7q/wCodWu3/DHQUVy8nxC0FPCVn4gWSeS3vpRb21ukJM8s5Yr5ITrvDKwI6DB5xzTrDxzZXXiBdBvtN1TTNXeMTLaXFr5v7okgSGSAyRquQR8zjnjuKdtbCvY6aqt9qMGnCFrsskUsgi83HyozHChj2yeAemSB3FeNeF9Q8P6nrmtLeeKtUvJrrXGstK0qPxNdLKkSkKz7Vm3bSQ7Zb+FRjrXpNl4SNv4FvvD2paheaolytyhnu7hppfLkZtg3tzlVKj6io5rR5vK/4J2/Eq3vcvn/AMC/4HTUVy3wz1+bxP8ADXRdVun8y5lt9k7/AN6RCUY/iVJ/GitJLlbRKd0SeOr57XQUtUhv2S/mW2nlsbOa4eGE5MjbYlZgSoKg44Zge1cR8RNUt77TtG1PwppOuyax4evI7izgXw9exiSLhZYQzQYAZPcfdFeuUVK0++5X9feedeLVZ/id8OdZVJEheW7t2WVCrKZbfcoIOCD8hGDzXSeN9fuPD3hW8udPsL+/1BoXW0gsrOW4Zpdp252Kdoz3OB+NXPEehpr+lrb+Z5NxBPHdWs+3PlTRsGVsdxkYI7gkd60LZ5ZLaNrmIQzEfPGG3BT3we49Dx9B0pSXNFx/qz/4NwTtJP8Ar+tjzjwx4ii8LfDvSdG0zRtfvtVit44vLfQ7uFDO/wB5nkeNVVQ7Es2emetR6Fcar4Wh8SWy6Ff33ijUdTnuIpUtHFtcBjiFjPzGiKgXKltwwcAk8+oUVUtW33/4D/QlaJLseQat4V/sHwH4e8O2UVxqviHTLhdQkm0x1FzbFmdpbhFfCsCxZVV8Bvcrinwa9pGj6br+r6RB4l1jxnNaiNodQ0yU3qZDeUnlxxKiRbgTuUBSR1JxXean4RivtdOtWGq6jo+ovAtvLPYtGRNGpJVWSVHQ4LNg7QeTzVzSdBh0q4mu3ubm/v7hFSa9u2UyOqklVwoVFA3HhVAySTzzUvVNPS//AA2ny/qxWzXW3/D6/O557omraZ4e+H2gWa6D4j1TU9IjWWOBNAu4y9yyMrku8QUDMj5Offnv6hG8kdgr3pjEqxAzFAQobHzYz2zmpqy/ENldaro82mWjeSLxTDNcZGYozw5A7sVJA7A8npgubck7bsUVa1+hy/wVtHtfhLpLygqbozXQB7LJK7r+hFFdvaWsFjZQ2lpGsUEEaxxRqMBVAwAPwFFVJpvTYSvu9yWiiipGFFFFABRRRQAUUUUAFFFFABRRRQB//9k=\"\u003e\u0026nbsp;is the variation of the logarithm of the energy spectrum; \u0026nbsp;the interval of frequency. These depths permit to constrain the 2D1/2 modeling and assimilate the geological structures to the reality. The average error on each gravity profile is estimated at 5% of the obtained depth (Bouba et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e; Nnangue et al. \u003cspan class=\"CitationRef\"\u003e2000\u003c/span\u003e).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv class=\"Section3\" id=\"Sec10\"\u003e\n \u003ch2\u003e3.2.2. 2D1/2 Modelling\u003c/h2\u003e\n \u003cp\u003eThe Modeling consists to calculate the theoretical anomaly from simple shape of the structure of model and to compare it to observed anomaly. The best obtained model is that which corresponds to the structure whose calculated anomaly is assimilated to the observed anomaly by adjustment (Poudjom-Djomani \u003cspan class=\"CitationRef\"\u003e1993\u003c/span\u003e). In this part, 2D1/2 modeling is obtained by using Grav2DC software based to algorithm of (Cooper \u003cspan class=\"CitationRef\"\u003e2004\u003c/span\u003e; Talwani et al. \u003cspan class=\"CitationRef\"\u003e1959\u003c/span\u003e). This modeling was carried out by taking into account the depths calculated by spectral analysis, the geology of the region and the density contrast of the anomalies sources. The density contrast is calculated from the formula, \u003cem\u003eC\u003csub\u003ei\u003c/sub\u003e = d\u003csub\u003e0\u003c/sub\u003e - d\u003csub\u003ei\u003c/sub\u003e\u003c/em\u003e where \u003cem\u003ed\u003csub\u003e0\u003c/sub\u003e = 2.65g/cm\u003csup\u003e3\u003c/sup\u003e\u003c/em\u003e is the average density of the granites, \u003cem\u003ed\u003csub\u003ei\u003c/sub\u003e\u003c/em\u003e is the average density of the ith formation (Noutchogwe et al. \u003cspan class=\"CitationRef\"\u003e2006\u003c/span\u003e).\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"4. Results","content":"\u003cdiv class=\"Section2\" id=\"Sec12\"\u003e\n \u003ch2\u003e4.1. Presentation of New Residual Bouguer Anomaly map\u003c/h2\u003e\n \u003cp\u003eThe residual anomaly map presented in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e shows two anomaly sectors: positive sector and negative sector.\u003c/p\u003e\n \u003cp\u003eThe first sector is located in west of Garoua, northeast of the study area and east of Dourbey. The values of anomalies are between (0 to 15mGal). It would be due to the presence of heavy rocks in granitic environment. The analyze of this map also shows another positive sector which extend from Bib\u0026eacute;mi to L\u0026eacute;r\u0026eacute; in Chad and include the Mayo Oulo-L\u0026eacute;re sedimentary basin which is located inside positive anomaly zone (15 to 35mGal). These anomalies show that the Mayo Oulo-L\u0026eacute;r\u0026eacute; basin does not have the morphology of sedimentary basin. It would correspond to a lake basin with a spectacular rise of heavy rocks probably basaltics.\u003c/p\u003e\n \u003cp\u003eThe second sector is constituted of negative anomalies. These anomalies are located in south of Garoua and around Dourbey where the Babouri-Figuil sedimentary basin is located. The values of these anomalies are between \u0026minus;\u0026thinsp;15 and \u0026minus;\u0026thinsp;5mGal. This could correspond to the sedimentary deposits of the Garoua trough in general and the Babouri-Figuil basin in particular. This basin constituted essentially of sandstone would be linked to the Benue trough. The Analysis of the map shows also another negative sector located in south of L\u0026eacute;r\u0026eacute; on Cameroon-Chad border. In this sector the minimum value of anomalies is -25mgal. This would indicate the presence of weak formations compared to the surrounding formations.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv class=\"Section2\" id=\"Sec13\"\u003e\n \u003ch2\u003e4.2. Estimation of Mean Depth of Density Interfaces\u003c/h2\u003e\n \u003cp\u003eIn this part, we used the spectral analysis to determine the depths of geological structures source of anomalies. Six profiles P1, P2, P3, P4, P5 and P6 have been traced on densified residual Bouguer anomaly map. P1, P2 and P3 were plotted on Babouri-Figuil sedimentary basin and P4, P5 and P6 on Mayo-Oulo-L\u0026eacute;r\u0026eacute; sedimentary basin. All these profiles are executed perpendicularly to the main elongation of the structure to be studied. When we plot the energy spectrum logarithm as a function of frequency, the spectral curve presents two characteristic slopes. The first slope located in the low frequencies corresponds to the deep structures. The second slope which represents the high frequencies corresponds to the bodies near surface.\u003c/p\u003e\n \u003cp\u003eIn Babouri-Figuil sedimentary basin, two major discontinuities have been obtained by spectral analysis on profiles P1, P2 and P3 (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eThe first discontinuity corresponds to deep structures with depths estimated at 4.70km, 4.55km and 5.46km respectively for profiles P1, P2 and P3. These depths could correspond to the sediment-granite contact zone. The second discontinuity is associated with bodies near surface. The estimated depths are: 1.48km, 1.44km and 1.58km respectively for profiles P1, P2 and P3. The average value of depth in this basin is around 1.50km. This result agrees with those obtained by (Schowoerer 1965; Ndjeng and Brunet \u003cspan class=\"CitationRef\"\u003e1998\u003c/span\u003e). According to these authors the depth of the sedimentary series does not exceed 1500m. Therefore the boundary between the lower crust and the upper crust of Babouri-Figuil sedimentary basin would be shallow.\u003c/p\u003e\n \u003cp\u003eIn Mayo-Oulo-L\u0026eacute;r\u0026eacute; sedimentary basin, two major discontinuities have been obtained on profiles P4, P5 and P6 (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eThe first discontinuity possesses the following depths 4.27km, 4.62km and 5.32km. These depths could correspond to the crust-mantle interface. The second discontinuity presents the following depths 1.48km, 1.54km and 1.72km. These depths are associated with intracrustal structures with an average depth of 1.55 km. This value probably corresponds to the near surface layer. It indicates that the Mayo Oulo-L\u0026eacute;r\u0026eacute; basin would be deeper than that of Babouri-Figuil.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv class=\"Section2\" id=\"Sec14\"\u003e\n \u003ch2\u003e4.3. Density and Density Contrast of Structures\u003c/h2\u003e\n \u003cp\u003eTo determine the characteristics and shapes of geological structures of suspected bodies in Babouri-Figuil and Mayo oulo-L\u0026eacute;r\u0026eacute; sedimentary basins, six profiles were modelized. P1, P2 and P3 of SE-NW direction were modelized in Babouri-Figuil sedimentary basin and P4, P5 and P6 of SW-NE direction in Mayo Oulo-L\u0026eacute;r\u0026eacute;. The average densities of sediments, granites and basaltic rocks present in the study area are respectively: 2.45g/cm\u003csup\u003e3\u003c/sup\u003e; 2.65g/cm\u003csup\u003e3\u003c/sup\u003e; 3g/cm\u003csup\u003e3\u003c/sup\u003e (Telord et al.1990). The corresponding density contrasts are respectively: -0.2g/cm\u003csup\u003e3\u003c/sup\u003e, 0g/cm\u003csup\u003e3\u003c/sup\u003e and 0.3g/cm\u003csup\u003e3\u003c/sup\u003e. In Babouri-Figuil sedimentary basin, we obtain three models of structures corresponding to profiles P1, P2 and P3. These models are constituted of two formations of different density contrast (Fig. \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003e- The first formation has density contrast and density respectively \u0026minus;\u0026thinsp;0.2g/cm\u003csup\u003e3\u003c/sup\u003e and 2.45g/cm\u003csup\u003e3\u003c/sup\u003e. This formation is present throughout the profile. Its depth varies and reaches a spectacular value of 5km, this formation would probably be responsible for a vast zone of negative Bouguer anomaly observed in the sedimentary basin. The density contrast associated with this formation permits to identify along the continental sediments.\u003c/p\u003e\n \u003cp\u003e- The second formation with density of 2.65g/cm\u003csup\u003e3\u003c/sup\u003e is associated to granites. It constitutes the substratum of the basin and it is presented as a rooted structure that extends to great depth.\u003c/p\u003e\n \u003cp\u003eIn Mayo Oulo-L\u0026eacute;r\u0026eacute; sedimentary basin, we obtain three models corresponding to profiles P4, P5 and P6. These models are constituted of three formations of different density contrast (Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003e- The first formation of density contrast \u0026minus;\u0026thinsp;0.2g/cm\u003csup\u003e3\u003c/sup\u003e has an average density of 2.45g/cm\u003csup\u003e3\u003c/sup\u003e. It is associated with continental sediments. This formation is present throughout the profile. It depth varies and reach a maximum depth of 3km.\u003c/p\u003e\n \u003cp\u003e- The second formation with an average density of 2.65g/cm\u003csup\u003e3\u003c/sup\u003e is associated to granites. The depth is an extension of this formation probably constitutes the substratum of the basin.\u003c/p\u003e\n \u003cp\u003e- The third formation with density contrast of +\u0026thinsp;0.3g/cm\u003csup\u003e3\u003c/sup\u003e has an average density of 2.95g/cm\u003csup\u003e3\u003c/sup\u003e. It is associated with basaltic rocks. To the SW of the profile, these basalts are near surface. The roof of this formation is decreasing and stabilizes at 1.5km. This roof drops to a depth of 3km to the NE of the profile. This formation would be formed during the cooling of magma inside the earth\u0026apos;s surface during the volcanic eruption.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"5. Discussion","content":"\u003cp\u003eEmpirical method of Zeng allows us to determine a regional anomaly which presents the best resemblance to the prolonged Bouguer anomaly at optimum altitude. This method testifies that the residual map of order 4 used in this work is an appropriate one. Negative anomalies observed on this residual map are due to the sedimentary cover while positive anomalies can be explained by the presence of basaltic rocks that were brought up tectonically to the surface. According to the spectral analysis, the depth in the negative anomaly (Babouri-Figuil) and positive anomaly (Mayo Oulo-L\u0026eacute;r\u0026eacute;) is very close. This is because the two basins are similar and shallow. The mean depths of Babouri-Figuil and Mayo Oulo-L\u0026eacute;r\u0026eacute; sedimentary basins were 1.50km and 1.55km respectively. These results agree with those obtained by (Ntsama 2013). According to these authors, Mayo Oulo-L\u0026eacute;r\u0026eacute; and Babouri-Figuil are small shallow Cretaceous basins filled with continental sediments and which depths do not exceed 1600m. For 2.5D subsurface modeling, the structure of the Babouri-Figuil and Mayo Oulo-L\u0026eacute;r\u0026eacute; presents many similarities in the composition of the upper crust when we observe profile P1 to P6. Some constraints and other geological considerations linked with the tectonic features of these basins were combined to build an accurate model for each profile. These constraints have been adopted to build the model corresponding to each anomaly such as the densities of anomalous masses. Densities have been either superior or inferior to the enclosing bed density, which was supposed to have homogenous mean density of 2.67g/cm\u003csup\u003e3\u003c/sup\u003e for the Babouri-Figuil and Mayo Oulo-L\u0026eacute;r\u0026eacute;. The mean densities of rocks present in the study area like granites, basaltics rocks and sedimentary formations were respectively supposed to be 2.65; 3; 2.45 g/cm\u003csup\u003e3\u003c/sup\u003e (Telford et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e1990\u003c/span\u003e; Zanga-Amougou et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). The interpretation of these models showed the presence of granites, basaltic rocks and sedimentary covers. Sedimentary formations have variable thickness with the maximum of about 5km found in Babouri-Figuil and around 3km in Mayo Oulo-L\u0026eacute;r\u0026eacute; sedimentary basin. The outflows of these sediments confirm the hypothesis showed in geological map. The following formation is constituted of granites. These granites are very abundant in the study area and their thickness are increasing in Babouri-Figuil and decreasing in Mayo Oulo-L\u0026eacute;r\u0026eacute; sedimentary basin. This could indicate that the uplift of granites is most significant in Babouri-Figuil. These models showed also basaltic rocks that generate positive residual anomaly. The origin of these rocks is found at great depth; it has cooled down and could not reach the earth\u0026rsquo;s surface. These results are compatible with the findings of (Kamguia et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2005\u003c/span\u003e) and the scheme proposed by (Ndjeng et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e1988\u003c/span\u003e) to explain the mechanism of magmatologic establishment of lavas in the Babouri-Figuil and Mayo-Oulo-L\u0026eacute;r\u0026eacute;.\u003c/p\u003e"},{"header":"6. Conclusions","content":"\u003cp\u003eThis work is based on the analysis and interpretation of combined gravity data of Babouri-Figuil and Mayo Oulo-L\u0026eacute;r\u0026eacute; sedimentary basins. The obtained new gravity anomaly map shows different geological structures partially or totally masked by the sedimentary cover. This map shows strong link between positive anomalies with basaltic rise and between negative anomalies with sedimentary deposits. For the choice of the residual anomaly we used the empirical method of Zeng. This method shows that the residual Bouguer anomaly map of order 4 is the best for an interpretation of crustal structures. The spectral analysis carried out in Babouri-Figuil and Mayo Oulo-L\u0026eacute;r\u0026eacute; sedimentary basins permit to determine the major discontinuities. The mean values of 1.50 km and 1.55 km are the new depth values obtained for future studies in these basins. The 2.5D modeling of the sources of residual anomalies highlights the structures having different densities or densities contrast. The various models show that Babouri-Figuil sedimentary basin is constituted of continental sediment which is situated on granitic environnement. The Mayo Oulo-L\u0026eacute;r\u0026eacute; sedimentary basin is constituted of sediments, basaltic rocks and granitic basement. For the future investigation we will use the 3D inversion, Horizontal Gradient Analysis and Euler deconvolution methods to improve and consolidate our results.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eEGM2008\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eEarth Gravitational Model 2008\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eORSTOM\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eOffice de Recherche Scientifique et Technique d\u0026rsquo;Outre Mer\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eBGI\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eBureau Gravim\u0026eacute;trique International\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eNGIA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eNational Geospatial-Intelligence Agency\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eUSA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eUnited States of America\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eICGEM\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eInternational Centre for Global Earth Models\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe would like to acknowledge the National Ge\u0026shy;ospatial-Intelligence Agency (NGIA) of USA and Bureau Gravimetrique International (BGI)\u0026nbsp;for compiling and making available the dataset used in this work.\u0026nbsp;Most of the figures in the paper were produced using Generic Mapping Tools software developed by Wessel and Smith for Exploration Geophysics. We also thank the anonymous reviewers for their helpful suggestions and comments.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eBS, AB, VO and LY designed the study area, proposed the methodology, analyzed and interpreted the gravity data by using various advanced processing techniques in consultation with JK and EMD. The manuscript was jointly prepared by BS, AB, VO, LY, JK and EMD.\u0026nbsp;All authors realized maps, discussed the results and contributed to the writing of the manuscript. All authors read and approved the final version of manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was supported by the personal fund of the authors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe terrestrial gravity and EGM2008 data use in this study are available respectively, at the BGI (Bureau Gravim\u0026eacute;trique International): https://bgi.obs-mip.fr/dataproducts/ and ICGEM (International Centre for Global Earth Models): http://icgem.gfz-potsdam.de/home\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors reveal that there are no conflicts of interest regarding the publication of this paper.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAbate Essi JM, Marcel J, Diab DA, Yene Atangana JQ, Abossolo Angue M, Mvondo Ondoa J (2019) Gravity Modeling of the Au-U Mineralized Crust at the North-Central Cameroon Illustrating Crutal Permeability. Nat Resour Res 29:473\u0026ndash;497. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s11053-019-09506-4\u003c/span\u003e\u003cspan address=\"10.1007/s11053-019-09506-4\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAbate Essi JM, Marcel J, Yene Atangana JQ, Diab AA, Dassou Fita E, Mbossi EF, Mvondo Ondoa J, Penaye J (2017) Interpretation of gravity data derived from the Earth Gravitational Model EGM2008 in the Center-North Cameroon: structural and mining implications. Arab J Geosci 10(130):1\u0026ndash;13. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://doi.org/10.1007/s12517-017-2919-y\u003c/span\u003e\u003cspan address=\"10.1007/s12517-017-2919-y\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAbdelrahman EM, Bayoumi AI, Abdelhady YE, Gobashi MM, El-Araby HM (1989) Gravity interpretation using correlation factors between successive least-squares residual anomalies. Geophysics 54(12):1521\u0026ndash;1663. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://doi.org/10.1190/1.1442629\u003c/span\u003e\u003cspan address=\"10.1190/1.1442629\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAbubakar AJ, Hashim M, Beiranvand AP (2018) Identification of hydrothermal alteration minerals associated with geothermal system using ASTER and Hyperion satellite data: a case study from Yankari Park, NE Nigeria. Geocarto Int 34(6):597\u0026ndash;625. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1080/10106049.2017.1421716\u003c/span\u003e\u003cspan address=\"10.1080/10106049.2017.1421716\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAllix P, Grosdidier E, Jardin\u0026eacute; S, Legoux O, Popoff M (1989) ) D\u0026eacute;couverte d\u0026rsquo;Aptien sup\u0026eacute;rieur \u0026agrave; Albien inf\u0026eacute;rieur dat\u0026eacute; par des microfossiles dans la s\u0026eacute;rie d\u0026eacute;tritique cr\u0026eacute;tac\u0026eacute;e du foss\u0026eacute; de la B\u0026eacute;nou\u0026eacute; (Nig\u0026eacute;ria). C R Acad Sci Paris 2(292):1291\u0026ndash;1295\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAllix P, Popoff M (983) Le Cr\u0026eacute;tac\u0026eacute; inf\u0026eacute;rieur de la partie nord-orientale du foss\u0026eacute; de la B\u0026eacute;nou\u0026eacute; (Nig\u0026eacute;ria): un exemple de relation \u0026eacute;troite entre tectonique et s\u0026eacute;dimentation. Bull. Rech. Explor. Prod. Elf-Aquitaine 7: 349\u0026ndash;359\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBessong M (2012) Pal\u0026eacute;oenvironnements et diagen\u0026egrave;se dans un r\u0026eacute;servoir gr\u0026eacute;seux d\u0026rsquo;\u0026acirc;ge cr\u0026eacute;tac\u0026eacute; du foss\u0026eacute; de la B\u0026eacute;nou\u0026eacute; au Nord Cameroun: les gr\u0026egrave;s de Garoua. Th\u0026egrave;se de Doctorat, Universit\u0026eacute; de Poitiers\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBonvalot S, Balmino G, Briais A, Kuhn M, Peyrefitte A, Vales N, Biancale R, Gabalda G, Moreaux G, Reinquin F, Sarrailh M (2012) WORLD GRAVITY MAP 1ST EDITION. Bureau Gravimetric international\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBouba A, Kamguia J, Tabod CT, Yap L, Nouayou R, Kande HL, Oyoa V (2017) Subsurface Structural Mapping Using Combined Terrestrial and Grace Gravity Data of the Adamawa Plateau (North-Cameroon). Int J G\u0026eacute;osciences 8(7):869\u0026ndash;887. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.4236/ijg.2017.87050\u003c/span\u003e\u003cspan address=\"10.4236/ijg.2017.87050\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBrunet M, Dejax J, Brillanceau A, Congleton J, Downs W, Duperon-Laudoueneix M, Eisenmann V, Flanagan K, Flynn L, Heintz E, Hell J, Jacobs L, Jehenne Y, Ndjeng E, Mouchelin G, Pilbeam D (1988) Mise en \u0026eacute;vidence d\u0026rsquo;une s\u0026eacute;dimentation pr\u0026eacute;coce d\u0026rsquo;\u0026acirc;ge Barr\u0026eacute;mien dans le foss\u0026eacute; de la B\u0026eacute;nou\u0026eacute; en Afrique occidentale (Bassin du Mayo Oulo L\u0026eacute;r\u0026eacute;, Cameroun), en relation avec l\u0026rsquo;ouverture de l\u0026rsquo;Atlantique Sud. C R Acad Sci Paris 306(II):1125\u0026ndash;1130\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eColin JP, Brunet M, Congleton JD, Dejax J, Flynn LJ (1992) Ostracodes lacustres des bassins d\u0026rsquo;\u0026acirc;ge cr\u0026eacute;tac\u0026eacute; inf\u0026eacute;rieur du Nord Cameroun: Hamakoussou, Koum et Babouri-Figuil. Revue paleobiol 11(2):357\u0026ndash;372\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCooper GRJ (2004) Euler deconvolution applied to potential field gradients. Explor Geophys 35:165\u0026ndash;170. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1071/EG04165\u003c/span\u003e\u003cspan address=\"10.1071/EG04165\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDanra Moh Guela GB, Tchameni R, Daouda D, Fosso Tchunte PM, Aw\u0026eacute; S, Biss\u0026eacute;gu\u0026eacute; JC (2019) Geological Mapping of the Panafrican Mokong Gneisess and Granitoides (Far North Cameroon): Contribution of Semi-automatic Processing from Landsat 8 OLI/TIRS Images. J Geosci Geomatics 7(2):80\u0026ndash;87. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.12691/jgg-7-2-4\u003c/span\u003e\u003cspan address=\"10.12691/jgg-7-2-4\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDejax J, Michard JG, Brunet M, et Hell J (1989) Empreintes de pas de Dinosauriens dat\u0026eacute;es du Cr\u0026eacute;tac\u0026eacute; inf\u0026eacute;rieur dans le bassin de Babouri-Figuil (foss\u0026eacute; de la B\u0026eacute;nou\u0026eacute;, Cameroun). J Geol Paleontology 1781:85\u0026ndash;108\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDimitriadis K, Tselentis GA, Thanassoulas (1987) Comput Geosci 13(5):549\u0026ndash;560. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/0098-3004(87)90056-2\u003c/span\u003e\u003cspan address=\"10.1016/0098-3004(87)90056-2\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. A basic program for 2-D spectralanalysis of gravity data and source-depth estimation\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFarhi W, Boudella A, Saibi H, Bounif MOA (2016) Integration of magnetic, gravity, and well data in imaging subsurface geology in the Ksar Hirane region (Laghouat, Algeria). J Afr Earth Sc 124:63\u0026ndash;74. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jafrearsci.2016.09.013\u003c/span\u003e\u003cspan address=\"10.1016/j.jafrearsci.2016.09.013\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGerard et Griveau (1972) Interpr\u0026eacute;tation quantitative en Gravim\u0026eacute;trie ou en Magn\u0026eacute;tisme \u0026agrave; partir de la carte transform\u0026eacute;e de gradient vertical. Geophys Prospect 20(2):459\u0026ndash;481. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/j.1365-2478.1972.tb00648.x\u003c/span\u003e\u003cspan address=\"10.1111/j.1365-2478.1972.tb00648.x\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGuiraud R, Maurin JC (1991) Le rifting en Afrique au Cr\u0026eacute;tac\u0026eacute; inf\u0026eacute;rieur: synth\u0026egrave;se structurale, mise en \u0026eacute;vidence de deux \u0026eacute;tapes dans la gen\u0026egrave;se des bassins, relations avec les ouvertures oc\u0026eacute;aniques p\u0026eacute;ri-africaines. Bull de Soci\u0026eacute;t\u0026eacute; G\u0026eacute;ologique de France 162(5):811\u0026ndash;823. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.2113/gssgfbull.162.5.811\u003c/span\u003e\u003cspan address=\"10.2113/gssgfbull.162.5.811\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJitendra V, Pala SK (2015) Geological mapping of Jharia Coalfield, India using GRACE EGM2008 gravity data: a vertical derivative approach. Geocarto Int 30(4):388\u0026ndash;401. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1080/10106049.2014.905637\u003c/span\u003e\u003cspan address=\"10.1080/10106049.2014.905637\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKamguia J, Manguelle-Dicoum E, Tabod CT, Tadjou JM (2005) Geological models deduced from gravity data in the Garoua basin, Cameroon. J Geophys Eng 2(2):147\u0026ndash;152. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1088/1742-2132/2/2/009\u003c/span\u003e\u003cspan address=\"10.1088/1742-2132/2/2/009\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKamguia J, Tabod CT, Nouayou R, Tadjou JM, Manguelle-Dicoum E, Kande HL (2007) The local geoid model of Cameroon CGM05. Nordic J Surveying Real Estate Res 4(2):7\u0026ndash;23. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://journal.fi/njs/article/view/1658\u003c/span\u003e\u003cspan address=\"https://journal.fi/njs/article/view/1658\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLouis P (1970) Contribution g\u0026eacute;ophysique \u0026agrave; la connaissance du bassin du lac Tchad. M\u0026eacute;moire OSTROM Paris 12:1\u0026ndash;311\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNdjeng E (1992) Etudes de la s\u0026eacute;dimentation et du mod\u0026egrave;le g\u0026eacute;odynamique de deux bassins du Cr\u0026eacute;tac\u0026eacute; inf\u0026eacute;rieur du Cameroun: Babouri-Figuil et Mayo Oulo-L\u0026eacute;r\u0026eacute;. Th\u0026egrave;se Doctorat \u0026egrave;s Sciences, Universit\u0026eacute; de Yaound\u0026eacute;\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNdjeng E (1994) Pole des caract\u0026egrave;res exoscopiques des grains de quartz des gr\u0026egrave;s de Garoua sur l\u0026rsquo;interpr\u0026eacute;tation du palo\u0026eacute;oenvironnement du bassin de la B\u0026eacute;nou\u0026eacute; du Cr\u0026eacute;tac\u0026eacute; sup\u0026eacute;rieur.Ann. Fac. Sci HS Chim. Sci. Nat73\u0026ndash;82\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNdjeng E, Brunet M (1998) Mod\u0026egrave;le d\u0026rsquo;\u0026eacute;volution g\u0026eacute;odynamique de deux bassins de l\u0026rsquo;Hauterivien\u0026ndash;Barr\u0026eacute;mien du Nord-Cameroun: les bassins de Babouri-Figuil et du Mayo Oulo-L\u0026eacute;r\u0026eacute; (Foss\u0026eacute; de la B\u0026eacute;nou\u0026eacute;). G\u0026eacute;oscience au Cameroun, pp 163\u0026ndash;165\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNdjeng E, Mouchelin G, Pilbeam D (1988) Mise en \u0026eacute;vidence d\u0026rsquo;une s\u0026eacute;dimentation pr\u0026eacute;coce d\u0026rsquo;\u0026acirc;ge Barr\u0026eacute;mien dans le foss\u0026eacute; de la B\u0026eacute;nou\u0026eacute; en Afrique occidentale (Bassin du Mayo Oulo L\u0026eacute;r\u0026eacute;, Cameroun), en relation avec l\u0026rsquo;ouverture de l\u0026rsquo;Atlantique Sud. C R Acad Sci Paris 306(II):1125\u0026ndash;1130\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNnangue JM, Ngako V, Fairhead JD, Ebinger CJ (2000) Depths to density discontinuities beneath the Adamawa plateau region, Central Africa, from spectral analyses of new and existing gravity data. J Afr Earth Sc 30(4):887\u0026ndash;901. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/S0899-5362(00)00058-0\u003c/span\u003e\u003cspan address=\"10.1016/S0899-5362(00)00058-0\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNoutchogwe TC, Tabod CT, Manguelle-Dicoum E (2006) A gravity study of the crust beneath the Adamawa fault zone, west central Africa. J Geophys Eng 3(1):82\u0026ndash;89. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1088/1742-2132/3/1/009\u003c/span\u003e\u003cspan address=\"10.1088/1742-2132/3/1/009\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNtsama Atangana JA (2013) Magn\u0026eacute;tostratigraphie et s\u0026eacute;dimentologie des formations cr\u0026eacute;tac\u0026eacute;esn des bassins s\u0026eacute;dimentaires d'Hamakoussou et du Mayo Oulo-L\u0026eacute;r\u0026eacute; au Nord-Cameroun (Foss\u0026eacute; de la B\u0026eacute;nou\u0026eacute;). Th\u0026egrave;se de Doctorat, Universit\u0026eacute; de Poitiers\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePalvis NK, Holmes SA, Kenyon SC, Factor JK (2008) An Eath Gravitational Model to degree 2160: EGM2008. Presented at the EGU General Assembly, Vienna, Austria, April 13 2008\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePalvis NK, Holmes SA, Kenyon SC, Factor JK (2012) The development and evaluation of the earth gravitational model 2008 (EGM2008). J Geophys Res 117(B4):1\u0026ndash;38. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1029/2011JB008916\u003c/span\u003e\u003cspan address=\"10.1029/2011JB008916\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePoudjom-Djomani YH (1993) Apport de la gravim\u0026eacute;trie \u0026agrave; l\u0026rsquo;\u0026eacute;tude de la lithosph\u0026egrave;re continentale et implications g\u0026eacute;odynamiques: \u0026eacute;tude d\u0026rsquo;un bombement intraplaque: le massif de l\u0026rsquo;Adamaoua (Cameroun). Th\u0026egrave;se de Doctorat, Universit\u0026eacute; de Paris Sud, Centre d\u0026rsquo;Orsay, p 294\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSaibi H, Nishijima J, Aboud E, Ehara S (2006) Euler deconvolution of gravity data in geothermal reconnaissance; the Obama geothermal area, Japan. J Explor Geophys Japan (Butsuri-Tansa) 59(3):275\u0026ndash;282. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3124/segj.59.275\u003c/span\u003e\u003cspan address=\"10.3124/segj.59.275\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTalwani M, Worzel JL, Landisman M (1959) Rapid gravity computations for two-dirnensional bodies with application to the Mendocino Submarine fracture zone. J Geoplqs Res 64(1):49\u0026ndash;59. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1029/JZ064i001p00049\u003c/span\u003e\u003cspan address=\"10.1029/JZ064i001p00049\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTelford WM, Geldart LP, Sheriff RE, Keys DA (1990) Applied Geophysics, 4th edition of National Conference on geophysics, Cambridge University Press. Cambridge United Kingdom, 860 p\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eToushmalani R, Saibi H (2015) Fast 3D inversion of gravity data using Lanczos bidiagonalization method. Arab J Geosci 8(7):4969\u0026ndash;4981. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi: 10.1007/s12517-014-1534-4\u003c/span\u003e\u003cspan address=\"https://doi: 10.1007/s12517-014-1534-4\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWeiyong Y, Rummel R (2013) A comparison of GOCE gravitational models with EGM2008. J Geodyn 73:14\u0026ndash;22. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jog.2013.10.004\u003c/span\u003e\u003cspan address=\"10.1016/j.jog.2013.10.004\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWessel P, Smith WHF (1995) New version of Generic Mapping Tools released. Eos Trans Am Geophys Union 76:329. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps:/doi.org/10.1029/95EO00198\u003c/span\u003e\u003cspan address=\"10.1029/95EO00198\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZanga-Amougou A, Ndougsa-Mbarga T, Meying A, Layu Yufenyu D, Bikoro-Bi-Alou M, Manguelle-Dicoum E (2013) 2.5D Modeling of Crustal Structures along the Eastern Cameroon and Western Central African Republic Derived from Finite Element and Spectral Analysis Methods. Geophysica 49(1):75\u0026ndash;97\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZeng H, Xu D, Tan H (2007) A model study for estimating optimum upward continuation height for gravity separation with application to a Bouguer gravity anomaly over a mineral deposit, Jilin province, northeast china. Geophysics 72(4):47\u0026ndash;71. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1190/1.2719497\u003c/span\u003e\u003cspan address=\"10.1190/1.2719497\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"EGM2008 model, Bouguer anomaly, Sedimentary basins, Residual anomaly, Empirical method, Spectral analysis, 2.5D modeling","lastPublishedDoi":"10.21203/rs.3.rs-1664918/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-1664918/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn this work, the crustal structure study of Babouri-Figuil and Mayo Oulo-L\u0026eacute;r\u0026eacute; sedimentary basins was carried out through the interpretation of gravity data. These data were obtained by combining to the terrestrial gravity data those obtained from EGM2008 model. The Analysis of the terrestrial Bouguer anomaly maps revealed negative and positive anomalies. Negative anomalies would be the signature of sedimentary basins while positive anomalies would be attributed to basaltic rocks under granitic environment. To isolate anomalies due to deep structures from those due to near surface structures, we used the empirical method. This method testifies that the residual map of order 4 is an appropriate one. In order to conduct the quantitative interpretation of the combined gravity data, six profiles were drawn on the residual Bouguer anomaly map and therefore were interpreted using spectral analysis and 2.5D modeling methods. The results indicate that the mean depths of mass sources near surface of Babouri-Figuil and Mayo Oulo-L\u0026eacute;r\u0026eacute; sedimentary basins were 1.50km and 1.55km respectively. Moreover, Babouri-Figuil is constituted of two formations of different density contrast while Mayo Oulo-L\u0026eacute;r\u0026eacute; shows three formations. These models helped us to clarify the geological structure of the study area. The results of the present study allow greater understanding the sedimentary basin thickness.\u003c/p\u003e","manuscriptTitle":"Gravity Study of the Crust beneath the Babouri-Figuil and Mayo Oulo-Léré Sedimentary Basins, North Cameroon and South Chad","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2022-06-02 14:26:36","doi":"10.21203/rs.3.rs-1664918/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"7bea7ce2-7c46-471c-b945-7d57a536bd38","owner":[],"postedDate":"June 2nd, 2022","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2022-10-29T13:44:24+00:00","versionOfRecord":[],"versionCreatedAt":"2022-06-02 14:26:36","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-1664918","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-1664918","identity":"rs-1664918","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}