Analyzing the Gravity Field of the Southern Desert of Iraq with its Possible Geological Implications Using Multi-Bidimensional Empirical Mode Decomposition Technique

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Al-Bahadily, Ali M. Al-Rahim This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-2849255/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 The Southern Desert of Iraq covers a vast region in southwest Iraq. The stratigraphic column comprises relatively thick sedimentary strata, which overlay a Neoproterozoic basement and dip gently towards the northeast. The ground surface is depicted by intensive karst forms of variable dimensions, especially within carbonate rocks of the Dammam Formation (Middle-Upper Eocene). In the present study, we use the Bidimensional Empirical Mode Decomposition technique for analyzing the gravity field into multi-residual fields and one regional. Analyzing and interpreting the resultant fields utilizing the geological data are the aims of this study. A free download MATLAB code is applied to the gravity data of the Southern Desert which is designed to separate the two-dimensional gridded gravity map into three residual maps and a regional one. These maps may reflect depths at different levels; shallow, intermediate, deep, and near the Moho discontinuity, respectively. According to the available information about the geology of the area, the residual maps can be interpreted in terms of shallow-depth geological structures, which have an economic interest in hydrocarbon exploration, intra-basement structures, and variation in the density of the basement terranes. The regional map, however, is interpreted to be related to a deep-seated gravity source most likely near the Moho. Further, the results illustrate an obvious relation between some of the gravity positives, in the first residual map, and the drilled exploration wells. This suggests a delineation of newly prospected structural highs. In addition, the second residual map shows gravity negatives that probably delineate basement basins/sub-basins. Geophysics Southern Desert of Iraq separation geological structures gravity interpretations Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction The study area is the Southern Desert which lies in the southwestern region of Iraq (Fig. 1 ). The area is smoothly elevated westwards from an altitude of 20 m to 400 m, where older rock units are exposed in the west. Seismic reflection survey faces a serious problem in discovering deep subsurface due to, partly, energy attenuation caused by extensive karst phenomena (Mohammed 2006 ). The deepest borehole, lies in the eastern part, shows that the U. Paleozoic rocks are found at a depth of 5.5 km. The Precambrian basement rocks, however, have not been reached by drilling yet. The Southern Desert includes several significant oilfields within Cretaceous formations, such as Khidhr Almaa in the south and Diwan, and Samawa in the east. The observed gravity field, as for other potential fields, is an accumulative sum of all effects of gravity sources lying between the center of the earth and the measuring station. Therefore, regardless of noise effects, the responses of gravity sources at different depth levels are combined to form a single observed gravity field. There is a need to take advantage of various methods of gravity field separation, especially since a lot of information about the subsurface is still unknown. This study is the first study that deals with analyzing the gravity field of the Southern Desert. Many field separation techniques, in the time and frequency domains, have been used in the geophysical literature to decompose the gravity field into a regional field, which usually reflects deep sources, and a residual field that reflects local or shallow sources. The accuracy of each technique depends on several factors including the geological setting, nature of anomalies, and noise level. Applying more than one separation technique and comparing the obtained results is desirable (Hinze et al. 2013 ) that can be integrated with geological information for the validity of the interpretation results. The Empirical Mode Decomposition (EMD) technique is one of the potential field separation techniques that works in the time domain. Al-Rahim ( 2016 ) applied the technique to the gravity data of Iraq to separate the gravity field into four components; three residuals and one regional indicating its preference over the polynomial regression technique. This contribution aims to analyze the gravity field of the Southern Desert into its main residual components utilizing the M-BEMD technique and present their geophysical meaning within a reasonable geological frame. This may move the geological view of the Southern Desert a step forward. 2. Geological Background The study area has a position within the Inner part of the Arabian Platform (Fouad 2015 ) which is tectonically stable (Buday and Jassim 1984 ). The area, according to the concepts of foreland basin systems (e.g. Catuneanu 2004 ), is associated with the evolution of the easterly located Mesopotamian Foredeep Basin along the Abu Jir fault system. This tectonic evolution led to the formation of two phases of plateaus (Ma’allah 2009) owing to enhanced fracture systems within the carbonate rock units and the onset of the karst system. The karst can be seen throughout the area within the exposed carbonate rocks of the Dammam Formation (M. – U. Eocene). The stratigraphic unite of the Southern Desert is shown in Fig. 2 . At a relatively shallow depth in the upper crust, there are many geological structural highs that have been targeted for hydrocarbon exploration since the seventies of the last century. These structures were initially explored by utilizing gravity survey data followed by seismic reflection surveys. ِAdditionally, all the exploration wells are drilled within the Phanerozoic cover and the depth range of target structures is between 1587–5483 m (Table 1 ). The Paleozoic in the study area is a complete petroleum system and offers potential for hydrocarbon exploration (Aqrawi, 1998). Table 1 Total depth of some exploration wells in the Southern Desert. No. ID Total depth in m (b.s.l) 1 SA1 3792 2 Si1 4127 3 Sw1 1587 4 Ubaid1 1603 5 Dn1 5483 Depth-to-basement was firstly estimated in a regional scale by the C.G.G (1974) between 5 and 8 km. 4. Gravity Data The national gravity survey provides coverage across the entire Iraq territory except for the highly folded zone and was jointly acquired by the Iraq Petroleum Company (IPC) and the Iraq Geological Survey (GEOSURV). The gravity coverage of the SD was initially surveyed by IPC in 1945. In the 1984, it was compiled with the other regions of the Iraq territory to produce the unified Bouguer gravity map of Iraq (Al-Kadhimi et al. 1984 ). The data have since been reprocessed and put in Geosoft database format as fully terrain-corrected Complete Bouguer products by GEOSURV and GETECH in 2011. The total station count is 121,119. The Southern Desert is covered by NS- and EW-oriented profiles with a profile spacing that varies from 4.0 to 5.5 km and a station spacing that ranges between a minimum of 0.5 km to ~ 1.0 km. The fieldwork procedure was carried out using a loop technique. Using Shuttle Radar Topography Mission (SRTM) satellite topography (Farr et al. 2007 ), the isostatic residual gravity field is calculated for the Complete Bouguer anomaly data, utilizing the Airy model and assuming isostatic equilibrium across the Inner Platform. A decompensative anomaly (DA) map, which is the product of differences between two grids; the isostatic residual and its 40 km upward continuation (Cordell et al. 1991 ), is obtained for the study area (Fig. 3 ). The DA map represents the gravity effects of the upper and middle crust. 3. Multi-bidimensional Empirical Mode Decomposition Technique The EMD technique, which was suggested by Huang et al. 1998 , has been used to analyze (decompose) a 1D non-stationary geophysical signal in a process called sifting into a trend called residue and intrinsic mode functions (IMF)s. Kim and Oh ( 2009 ) gave a useful example of applying the EMD to a synthetic time-series signal, X(t), and explained the process of sifting and the results. The signal, shown in Fig. 2 A, is initially composed of summing four sinusoidal functions that can be decomposed into its components by the process of sifting through three steps illustrated by Huang et al. ( 1998 ). In the first step is to recognize the local extrema of X(t) (see Fig. 2 B(a)), and produce two functions named the upper and lower envelopes through interpolation of local highs and local lows, respectively (see Fig. 2 B(b)). The second step is to take their mean which produces a lower component of frequencies than the initial signal as illustrated in Fig. (2B(c)). Then subtraction mean of the envelope from X(t), hence, the high-frequency content is isolated as shown in Fig. 2 B(d). A periodic signal is defined by Huang et al. ( 1998 ) as an Intrinsic Mode Function (IMF) if it meets two states; first, the number of highs varies from the number of zero crossings by 1, and second, the local mean = 0. If the states of IMF are not met after a repetition of the above-mentioned process, the same process is employed on the remaining wave as presented in Fig. 2 d-f until the attributes of IMF are met. Actually, with repeated sifting, the low-amplitude riding signals can be recovered, and the sifting works for eliminating the overriding different wave frequencies and makes the resultant signals analogous (Huang et al. 1998 ). The technique has been extended to cover 2D (grid) called Bidimensional Empirical Mode Decomposition (BEMD) used in image processing, texture analysis, and gravity data separation (Huang et al. 2010 ). The technique is applied to the gravity data of the Southern Desert utilizing a MATLAB function prepared by Sasikanth (code retrieved in 2021). Application the code allows decomposition of the observed field into three residual 2D maps called IMF1-3 and one 2D regional map called residue; therefore, this technique is called here Mulit-Bidimentional Empirical Mode Decomposition (M-BEMD). Results of Applying M-BEMD Technique The DA grid has been decomposed into four components utilizing the BEMD algorithm. Three components are intrinsic mode functions, 1IMF, 2IMF, and 3IMF and the fourth component is a residue. The three IMFs represent the residual fields at different depth levels; shallow (1IMF), intermediate (2IMF), and deep (3IMF), whilst the residue represents the regional field at a deeper level that cannot further be decomposed. Anomalies in the IMF1, IMF2, IMF3, and the residue maps are respectively shown in Fig. 4 a, b, c, and d. Figure 4 a-d shows that some anomalies in the IMFs go on from a deeper level to a shallower level i.e. from the basement to the upper sedimentary cover or from lower sedimentary layers to upper layers indicating their deep roots, for example, the area outlined by the black box. 5. Discussion Analyzing the gravity field of the Southern Desert by using the M-BEMD technique is a separation method based on the main wavelength bands that are dominated the field. The IMF1,2, and 3 could be representative of three wavelength bands; short, intermediate, and long, respectively. According to the general relation between the wavelength and depth, the IMF1 map (Fig. 4 a), reflects the shorter wavelength band that can be isolated using the MATLAB algorithm. This band is supposed to be at shallow depths within the upper part of the sedimentary cover and it reflects the gravity effects at this depth level. No wavelength shorter than that appears in the IMF1, which may reflect a shallower depth close to the ground surface (near-surface density inhomogeneity) can be detected. This is a limitation of this technique/algorithm since the density variations resulting from relatively small-scale karst forms are most probably not included in the IMF1. However, karst forms are often complicated and have different sizes and shapes (Sissakian et al. 2013 ; Al-Bahadily et al. 2022) and could be extended for long distances following the dominant regional fracture systems. Figures (5) shows an image of a large karst form located on the southern edge of Salman Depression; the largest depression in the study area close to its central part (Fig. 1 ). Hence, the karst forms that have regional scale are implied in the IMF1 anomalies. The drilled hydrocarbon boreholes are superimposed on the IMF1 map (and also other analyzed maps) where a clear relationship between these boreholes and positive gravity residuals, which could be interpreted as structural highs, is noticed. This may confirm that the IMF1 anomalies are reflected from relatively shallow depths in the upper crust (see depths in Table 1 ). Additionally, it shows that the tectonic stresses resulting from the Arabian-Eurasian (Iranian part) plate’s collision have influenced the upper part of the sedimentary cover of the Southern Desert. In the IMF2 map (Fig. 4 b), the intermediate wavelength band is represented and the gravity anomalies are related to deeper sources more likely are an expression of the basement surface. This may be evident from the density of zero contours (white-colored lines) which appear less than in IMF1 indicating broader and deeper anomaly sources. Some boreholes still have relation with gravity highs suggesting deep-seated source roots for these sources whereas others are not. The amplitudes of the anomalies are higher than in IMF1 that reflects the distribution of relatively high-density masses that almost existed in basement structures. The IMF3 map (Fig. 4 c) displays anomalies of long wavelength band. It is expected to be related to the density distribution of deep basement terranes. Moreover, these anomalies reflect basement lithological variations since the amplitude values are relatively the highest among other IMFs (IMF1 and IMF2). In this case, a nearly NS trending high-density basement terrane is clearly shown (delineated by white color contours in Fig. 4 c). The residue map (Fig. 4 d) expresses the deepest level which can not be defined in terms of wavelength-related structure, i.e. needs a larger area to be analyzed, and it represents the more regional gravity field that ends the analyzing process. The residue map indicates that some of the deep gravity sources have not been removed from the DA map when the 40 km upward-continuation filtering has been employed. This simply may be revealed from the rule of the width of an anomaly equals three times its depth (Fig. 4 d, the positive anomaly). The boreholes have almost no direct relation to the anomalies that appear in Fig. 4 c and d and they are posted for comparison with the IMF1 and IMF2 maps (Fig. 4 a and b). As mentioned earlier, the M-BEMD technique isolates the gravity anomalies according to their wavelengths, however, anomalies are normally of broadband wavelengths that can be separated into more than one IMF. Accordingly, we may notice that some anomalies exist in two IMF maps for example, the anomaly area outlined by the black box in Fig. 4 . Additionally, the occurrence of geological structures, shown in IMF1, which are targets of hydrocarbon prospecting, refers to the tectonic stresses affecting the area including the sedimentary strata. 6. Conclusions The gravity field of the Southern Desert of Iraq has been analyzed into three residual fields and one regional utilizing the M-BEMD technique. These fields could be useful in assisting in the qualitative interpretation stage and could be linked with any quantitative geophysical work in the area. The three fields reflect different wavelength bands that may be classified into short-, intermediate-, and long- wavelength bands. Further, they could coincide with geological structures at shallow depths in the upper crust, upper basement surface relief (structures), and lithological variations in the deep basement terranes. The regional, however, may express the deeper part most likely at a depth level near the Moho. The positive anomalies in the short wavelength band map show a clear relation with the previously drilled hydrocarbon wells indicating good isolation for the geological structures and allowing for discovering new prospective hydrocarbon reservoirs. The map of anomalies in the intermediate band could reflect basement topography and show prospected regions of the distribution of basins/sub-basins. A broad nearly NS trending positive anomaly is a distinctive long band that could represent relatively high-density rocks of basic origin. Declarations Acknowledgments We would like to express our thanks to the Iraq Geological Survey (GEOSURV) for its role in providing the necessary data for this study. Competing interests: The authors declare no competing interests. References Al-Bahadily HA, Al-Rahim AM, Long AJ (2022a) Postulated Precambrian Basement of the Iraq Southern Desert: A new look utilizing magnetic data. Mediterranean Geosciences Union Annual Meeting (MedGU-21) , Extended abstract (in press). Al-Bahadily HA, Long AJ, Al-Rahim AM (2022b) Determination of Karst Terrane and Defining Deep Structure by Gravity, Southern Desert, Iraq. Mediterranean Geosciences Union Annual Meeting (MedGU-21) , Extended abstract no. 89 (in press). Al-Kadhimi JAM, Fattah AS, Abbas MJ (1984) Unified Bouguer gravity data of Iraq, GEOSURV Library , Baghdad, Iraq. Al-Rahim AM (2016) Separating the gravity field of Iraq by using bidimensional empirical mode decomposition technique. Arab J Geosci 9:43. Buday T, Jassim SZ (1984) Geological map of Iraq 1:1000,000 Scale Series, sheet No. 2, Tectonic Map of Iraq. Publication of GEOSURV , Baghdad, Iraq. Catuneanu O (2004) Retroarc foreland systems––evolution through time Geological Society of Africa Presidential Review. Journal of African Earth Sciences 38 (7): 225–242. C.G.G. (Compagnie General de Geophysique) (1974) Aeromagnetic and Aerospectrometric survey of Iraq. GEOSURV Library , rep. no. 2642. Cordell L, Zorin Y, Keller G (1991) The decompensative gravity anomaly and deep structure of the region of the Rio Grande Rift, JGR , 96 (B4):6557–6568. Farr TG, Rosen PA, Caro E, Crippen R, Duren R, Hensley S, Kobrick M, Paller M, Rodriguez E, Roth L, Seal D, Shaffer S, Shimada J, Umland J, Werner M, Oskin M, Burbank D, Alsdorf D (2007) The Shuttle Radar Topography Mission, Rev. Geophys. , 45: RG2004. Fouad SF (2015) Tectonic Map of Iraq, scale 1: 1000 000, 3rd edit., Iraqi Bull. Geol. Min . 11:1–7. GEOSURV, GETECH Group plc. (2011) Aeromagnetic and gravity data for Iraq; reprocessing, compilation and databasing the aeromagnetic and gravity data of Iraq. GEOSURV Library . rep. no. G1116. Hinze W, Von Frese, R., Saad, A. (2013). Gravity data processing. In Gravity and Magnetic Exploration: Principles, Practices, and Applications (pp. 122–174). Cambridge: Cambridge University Press. doi: 10.1017/CBO9780511843129.007 . Huang N E, Shen Z, Long SR, Wu MC, Shih HH, Zheng Q, Yen N-C, Tung CC, Liu HH (1998) The empirical mode decomposition and the Hilbert spectrum for nonlinear and nonstationary time series analysis. Proc R Soc Lond A 454:903–993. Huang JN, Zhao BB, Chen YQ, Zhao PD (2010) Bidimensional empirical mode decomposition (BEMD) for extraction of gravity anomalies associated with gold mineralization in the Tongshi gold field, western Shangdong uplifted block, eastern China. Computers & Geosciences 36(7):987–995. Kim D, Oh H-S (2009) EMD: a package for empirical mode decomposition and Hilbert spectrum. R Journal 1(1):40–64. Jassim SZ “Late Precambrian development of Arabian Plate” Geology of Iraq. Edited by SZ Jassim and JC Goff (2006) Dolin, Prague, pp. 27–31. Jassim SZ, Buday T “Tectonic Framework.” Geology of Iraq. Edited by SZ Jassim, JC Goff (2006) Dolin, Prague, pp. 45–56. Ma’ala KhA (2009) Geology of Iraqi Southern Desert: Geomorphology. Iraqi Bull. Geol. Min. Special Issue:7–33. Melo FF, Barbosa Valé CF (2020) Reliable Euler deconvolution estimates throughout the vertical derivatives of the total-field anomaly, Computers and Geosciences. 138, 10443. Mohammed SAG (2006) Megaseismic section across the northeastern slope of the Arabian Plate, Iraq. GeoArabia,11(4):77–90. Sasikanth (2021) Bidimensional Emperical Mode Decomposition (BEMD) ( https://www.mathworks.com/matlabcentral/fileexchange/28761-bi-dimensional-emperical-mode-decomposition-bemd ), MATLAB Central File Exchange. Retrieved July 23, 2021. Sissakian VK, Mahmoud AA, Awad AM (2013) Genesis and age determination of Al-Salman Depression, South Iraq. Iraqi Bulletin of Geology and Mining . 9 (1):1–19. Tamar-Agha MY, Al-Sagri KhEA (2015) Shading further lights on the Upper Cretaceous –Neogene subsurface lithostratigraphy of the Southwestern Iraq. Journal of Science, 56(1C):798–827. 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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-2849255","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":194198812,"identity":"6572a346-177e-4a59-928e-4ecf6bec8ca5","order_by":0,"name":"Hayder A. Al-Bahadily","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABCUlEQVRIiWNgGAWjYBACAyCWALMOAHHiPxsgydh4gHgtD9jSQFoaiNfC+IDtMFw7TmDOfsbwxsc9DPJ8t5ufPUjgOW+3tv0w0JYam2hcWix7cowtZzxjMJx555i5QYLE7eRtZxKBWo6l5TbgctiBHDNpngMMjBtuJJhJJBjcTjY7ANTC2HAYt5bzb8yk/xxgsN9wI/2bRELCuWSz8w8JaLkBtAXo3cQNQIZEwoEDdmY3CNly41mxZc8BieSZN3LKJBIbkhPMbgBtScDnl/PJG2/8OGBj23cjfZvkzwY7e7Pz6Q8ffKixwamFgYEDETUgkAhWmYBTOQiwP0Dh2uNVPApGwSgYBSMSAABckWrIFgqo6QAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0003-1970-5863","institution":"Iraq Geological Survey","correspondingAuthor":true,"prefix":"","firstName":"Hayder","middleName":"A.","lastName":"Al-Bahadily","suffix":""},{"id":194198813,"identity":"01253fc6-9710-4009-92a9-8281d1bf863a","order_by":1,"name":"Ali M. Al-Rahim","email":"","orcid":"https://orcid.org/0000-0002-6182-5976","institution":"University of Baghdad","correspondingAuthor":false,"prefix":"","firstName":"Ali","middleName":"M.","lastName":"Al-Rahim","suffix":""}],"badges":[],"createdAt":"2023-04-22 19:44:31","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-2849255/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-2849255/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":36297259,"identity":"f5f50afd-38bc-4476-992c-e613bdb2c898","added_by":"auto","created_at":"2023-04-25 22:49:40","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":558204,"visible":true,"origin":"","legend":"\u003cp\u003eLocation map of the Iraq Southern Desert (study area) shows the main valleys\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-2849255/v1/40989dcadc7b55fa696c3313.png"},{"id":36297262,"identity":"68d2ff41-42f3-4e7e-9e71-1eac2cb1a37b","added_by":"auto","created_at":"2023-04-25 22:49:40","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":346621,"visible":true,"origin":"","legend":"\u003cp\u003eStratigraphy of the Southern Desert deduced from boreholes intersection (after Tamar Agha and Al-Sagri 2015). TMS is Tectonostratigraphic Megasequence. The slash lines indicate a time gap.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-2849255/v1/b854197544b920392b551326.jpg"},{"id":36297261,"identity":"547a80ad-8f31-4351-86fe-32faa7819668","added_by":"auto","created_at":"2023-04-25 22:49:40","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":601880,"visible":true,"origin":"","legend":"\u003cp\u003eFig 2. Application of Empirical Mode Decomposition (EMD) technique on a time series function that decomposes the function, by a process of sifting, into its components. (A) A sinusoidal function; X(t) having 4 components. (B) Steps of the sifting process. (C) Results of implementing the EMD on the data in (A) (after Kim and Oh 2009).\u003c/p\u003e","description":"","filename":"21.jpg","url":"https://assets-eu.researchsquare.com/files/rs-2849255/v1/5208adef342ce91eb61e606b.jpg"},{"id":36297639,"identity":"44fc4f1e-a92a-4fa8-83b7-f591c79f63df","added_by":"auto","created_at":"2023-04-25 22:57:40","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":496795,"visible":true,"origin":"","legend":"\u003cp\u003eFig 3. Decompensative Anomaly (DA) map of the Southern Desert. The gravity field has been decomposed into three residuals and one regional that are utilized in geological interpretation (Al-Kadhimi et al. 1984; GEOSURV and GETECH 2011).\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-2849255/v1/2d67ff32c2ec2637b773419f.jpg"},{"id":36297640,"identity":"6dcd8958-d555-4f49-9ade-c67f06ef6eaa","added_by":"auto","created_at":"2023-04-25 22:57:40","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1635760,"visible":true,"origin":"","legend":"\u003cp\u003eFig 4. Implement of M-BEMD on the gravity data of the study area. (a) IMF1, (b) IMF2, (c) IMF3, (d) a residue. IMFs from 1 to 3 represent residual fields at different depths; shallow, intermediate, and deep, respectively. The residue represents the regional field that can not be further decomposed. White contours have a zero value.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-2849255/v1/a2087ee8e33c39318b6bc1bc.jpg"},{"id":36297264,"identity":"f3c77842-b298-4e9c-ad88-35d44d7b7771","added_by":"auto","created_at":"2023-04-25 22:49:40","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":284416,"visible":true,"origin":"","legend":"\u003cp\u003eFig 5. Image of a karst feature in the southern part of Salman Depression close to the central part of the Southern Desert within the carbonate rocks of the Dammam Formation (after Sissakian et al. 2013).\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-2849255/v1/2c74f36974de6d67cbb5acd8.jpg"},{"id":36297641,"identity":"8e9c10a6-d7e9-4a71-9952-0f6489864437","added_by":"auto","created_at":"2023-04-25 22:57:46","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1501131,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-2849255/v1/8ded1df7-3727-4866-aed2-a23f06164b23.pdf"}],"financialInterests":"","formattedTitle":"\u003cp\u003e\u003cstrong\u003eAnalyzing the Gravity Field of the Southern Desert of Iraq with its Possible Geological Implications Using Multi-Bidimensional Empirical Mode Decomposition Technique\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe study area is the Southern Desert which lies in the southwestern region of Iraq (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The area is smoothly elevated westwards from an altitude of 20 m to 400 m, where older rock units are exposed in the west. Seismic reflection survey faces a serious problem in discovering deep subsurface due to, partly, energy attenuation caused by extensive karst phenomena (Mohammed \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). The deepest borehole, lies in the eastern part, shows that the U. Paleozoic rocks are found at a depth of 5.5 km. The Precambrian basement rocks, however, have not been reached by drilling yet. The Southern Desert includes several significant oilfields within Cretaceous formations, such as Khidhr Almaa in the south and Diwan, and Samawa in the east.\u003c/p\u003e \u003cp\u003eThe observed gravity field, as for other potential fields, is an accumulative sum of all effects of gravity sources lying between the center of the earth and the measuring station. Therefore, regardless of noise effects, the responses of gravity sources at different depth levels are combined to form a single observed gravity field. There is a need to take advantage of various methods of gravity field separation, especially since a lot of information about the subsurface is still unknown. This study is the first study that deals with analyzing the gravity field of the Southern Desert.\u003c/p\u003e \u003cp\u003eMany field separation techniques, in the time and frequency domains, have been used in the geophysical literature to decompose the gravity field into a regional field, which usually reflects deep sources, and a residual field that reflects local or shallow sources. The accuracy of each technique depends on several factors including the geological setting, nature of anomalies, and noise level. Applying more than one separation technique and comparing the obtained results is desirable (Hinze et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) that can be integrated with geological information for the validity of the interpretation results. The Empirical Mode Decomposition (EMD) technique is one of the potential field separation techniques that works in the time domain. Al-Rahim (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2016\u003c/span\u003e) applied the technique to the gravity data of Iraq to separate the gravity field into four components; three residuals and one regional indicating its preference over the polynomial regression technique.\u003c/p\u003e \u003cp\u003eThis contribution aims to analyze the gravity field of the Southern Desert into its main residual components utilizing the M-BEMD technique and present their geophysical meaning within a reasonable geological frame. This may move the geological view of the Southern Desert a step forward.\u003c/p\u003e"},{"header":"2. Geological Background","content":"\u003cp\u003eThe study area has a position within the Inner part of the Arabian Platform (Fouad \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e) which is tectonically stable (Buday and Jassim \u003cspan class=\"CitationRef\"\u003e1984\u003c/span\u003e). The area, according to the concepts of foreland basin systems (e.g. Catuneanu \u003cspan class=\"CitationRef\"\u003e2004\u003c/span\u003e), is associated with the evolution of the easterly located Mesopotamian Foredeep Basin along the Abu Jir fault system. This tectonic evolution led to the formation of two phases of plateaus (Ma\u0026rsquo;allah 2009) owing to enhanced fracture systems within the carbonate rock units and the onset of the karst system. The karst can be seen throughout the area within the exposed carbonate rocks of the Dammam Formation (M. \u0026ndash; U. Eocene). The stratigraphic unite of the Southern Desert is shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\n\u003cp\u003eAt a relatively shallow depth in the upper crust, there are many geological structural highs that have been targeted for hydrocarbon exploration since the seventies of the last century. These structures were initially explored by utilizing gravity survey data followed by seismic reflection surveys. ِAdditionally, all the exploration wells are drilled within the Phanerozoic cover and the depth range of target structures is between 1587\u0026ndash;5483 m (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). The Paleozoic in the study area is a complete petroleum system and offers potential for hydrocarbon exploration (Aqrawi, 1998).\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab1\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eTotal depth of some exploration wells in the Southern Desert.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eNo.\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eID\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eTotal depth in m (b.s.l)\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eSA1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e3792\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eSi1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e4127\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eSw1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e1587\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eUbaid1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e1603\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDn1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e5483\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/div\u003e\n\u003cp\u003eDepth-to-basement was firstly estimated in a regional scale by the C.G.G (1974) between 5 and 8 km.\u003c/p\u003e"},{"header":"4. Gravity Data","content":"\u003cp\u003eThe national gravity survey provides coverage across the entire Iraq territory except for the highly folded zone and was jointly acquired by the Iraq Petroleum Company (IPC) and the Iraq Geological Survey (GEOSURV). The gravity coverage of the SD was initially surveyed by IPC in 1945. In the 1984, it was compiled with the other regions of the Iraq territory to produce the unified Bouguer gravity map of Iraq (Al-Kadhimi et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e1984\u003c/span\u003e). The data have since been reprocessed and put in Geosoft database format as fully terrain-corrected Complete Bouguer products by GEOSURV and GETECH in 2011. The total station count is 121,119. The Southern Desert is covered by NS- and EW-oriented profiles with a profile spacing that varies from 4.0 to 5.5 km and a station spacing that ranges between a minimum of 0.5 km to ~\u0026thinsp;1.0 km. The fieldwork procedure was carried out using a loop technique.\u003c/p\u003e \u003cp\u003eUsing Shuttle Radar Topography Mission (SRTM) satellite topography (Farr et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2007\u003c/span\u003e), the isostatic residual gravity field is calculated for the Complete Bouguer anomaly data, utilizing the Airy model and assuming isostatic equilibrium across the Inner Platform. A decompensative anomaly (DA) map, which is the product of differences between two grids; the isostatic residual and its 40 km upward continuation (Cordell et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e1991\u003c/span\u003e), is obtained for the study area (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The DA map represents the gravity effects of the upper and middle crust.\u003c/p\u003e"},{"header":"3. Multi-bidimensional Empirical Mode Decomposition Technique","content":"\u003cp\u003eThe EMD technique, which was suggested by Huang et al. \u003cspan class=\"CitationRef\"\u003e1998\u003c/span\u003e, has been used to analyze (decompose) a 1D non-stationary geophysical signal in a process called sifting into a trend called residue and intrinsic mode functions (IMF)s. Kim and Oh (\u003cspan class=\"CitationRef\"\u003e2009\u003c/span\u003e) gave a useful example of applying the EMD to a synthetic time-series signal, X(t), and explained the process of sifting and the results. The signal, shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eA, is initially composed of summing four sinusoidal functions that can be decomposed into its components by the process of sifting through three steps illustrated by Huang et al. (\u003cspan class=\"CitationRef\"\u003e1998\u003c/span\u003e). In the first step is to recognize the local extrema of X(t) (see Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eB(a)), and produce two functions named the upper and lower envelopes through interpolation of local highs and local lows, respectively (see Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eB(b)). The second step is to take their mean which produces a lower component of frequencies than the initial signal as illustrated in Fig.\u0026nbsp;(2B(c)). Then subtraction mean of the envelope from X(t), hence, the high-frequency content is isolated as shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eB(d). A periodic signal is defined by Huang et al. (\u003cspan class=\"CitationRef\"\u003e1998\u003c/span\u003e) as an Intrinsic Mode Function (IMF) if it meets two states; first, the number of highs varies from the number of zero crossings by 1, and second, the local mean\u0026thinsp;=\u0026thinsp;0. If the states of IMF are not met after a repetition of the above-mentioned process, the same process is employed on the remaining wave as presented in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ed-f until the attributes of IMF are met. Actually, with repeated sifting, the low-amplitude riding signals can be recovered, and the sifting works for eliminating the overriding different wave frequencies and makes the resultant signals analogous (Huang et al. \u003cspan class=\"CitationRef\"\u003e1998\u003c/span\u003e).\u003c/p\u003e\n\u003cp\u003eThe technique has been extended to cover 2D (grid) called Bidimensional Empirical Mode Decomposition (BEMD) used in image processing, texture analysis, and gravity data separation (Huang et al. \u003cspan class=\"CitationRef\"\u003e2010\u003c/span\u003e).\u003c/p\u003e\n\u003cp\u003eThe technique is applied to the gravity data of the Southern Desert utilizing a MATLAB function prepared by Sasikanth (code retrieved in 2021). Application the code allows decomposition of the observed field into three residual 2D maps called IMF1-3 and one 2D regional map called residue; therefore, this technique is called here Mulit-Bidimentional Empirical Mode Decomposition (M-BEMD).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults of Applying M-BEMD Technique\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe DA grid has been decomposed into four components utilizing the BEMD algorithm. Three components are intrinsic mode functions, 1IMF, 2IMF, and 3IMF and the fourth component is a residue. The three IMFs represent the residual fields at different depth levels; shallow (1IMF), intermediate (2IMF), and deep (3IMF), whilst the residue represents the regional field at a deeper level that cannot further be decomposed. Anomalies in the IMF1, IMF2, IMF3, and the residue maps are respectively shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ea, b, c, and d. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ea-d shows that some anomalies in the IMFs go on from a deeper level to a shallower level i.e. from the basement to the upper sedimentary cover or from lower sedimentary layers to upper layers indicating their deep roots, for example, the area outlined by the black box.\u003c/p\u003e"},{"header":"5. Discussion","content":"\u003cp\u003eAnalyzing the gravity field of the Southern Desert by using the M-BEMD technique is a separation method based on the main wavelength bands that are dominated the field. The IMF1,2, and 3 could be representative of three wavelength bands; short, intermediate, and long, respectively. According to the general relation between the wavelength and depth, the IMF1 map (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ea), reflects the shorter wavelength band that can be isolated using the MATLAB algorithm. This band is supposed to be at shallow depths within the upper part of the sedimentary cover and it reflects the gravity effects at this depth level. No wavelength shorter than that appears in the IMF1, which may reflect a shallower depth close to the ground surface (near-surface density inhomogeneity) can be detected. This is a limitation of this technique/algorithm since the density variations resulting from relatively small-scale karst forms are most probably not included in the IMF1. However, karst forms are often complicated and have different sizes and shapes (Sissakian et al. \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e; Al-Bahadily et al. 2022) and could be extended for long distances following the dominant regional fracture systems. Figures\u0026nbsp;(5) shows an image of a large karst form located on the southern edge of Salman Depression; the largest depression in the study area close to its central part (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). Hence, the karst forms that have regional scale are implied in the IMF1 anomalies.\u003c/p\u003e\n\u003cp\u003eThe drilled hydrocarbon boreholes are superimposed on the IMF1 map (and also other analyzed maps) where a clear relationship between these boreholes and positive gravity residuals, which could be interpreted as structural highs, is noticed. This may confirm that the IMF1 anomalies are reflected from relatively shallow depths in the upper crust (see depths in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). Additionally, it shows that the tectonic stresses resulting from the Arabian-Eurasian (Iranian part) plate\u0026rsquo;s collision have influenced the upper part of the sedimentary cover of the Southern Desert.\u003c/p\u003e\n\u003cp\u003eIn the IMF2 map (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eb), the intermediate wavelength band is represented and the gravity anomalies are related to deeper sources more likely are an expression of the basement surface. This may be evident from the density of zero contours (white-colored lines) which appear less than in IMF1 indicating broader and deeper anomaly sources. Some boreholes still have relation with gravity highs suggesting deep-seated source roots for these sources whereas others are not. The amplitudes of the anomalies are higher than in IMF1 that reflects the distribution of relatively high-density masses that almost existed in basement structures.\u003c/p\u003e\n\u003cp\u003eThe IMF3 map (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ec) displays anomalies of long wavelength band. It is expected to be related to the density distribution of deep basement terranes. Moreover, these anomalies reflect basement lithological variations since the amplitude values are relatively the highest among other IMFs (IMF1 and IMF2). In this case, a nearly NS trending high-density basement terrane is clearly shown (delineated by white color contours in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ec).\u003c/p\u003e\n\u003cp\u003eThe residue map (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ed) expresses the deepest level which can not be defined in terms of wavelength-related structure, i.e. needs a larger area to be analyzed, and it represents the more regional gravity field that ends the analyzing process.\u003c/p\u003e\n\u003cp\u003eThe residue map indicates that some of the deep gravity sources have not been removed from the DA map when the 40 km upward-continuation filtering has been employed. This simply may be revealed from the rule of the width of an anomaly equals three times its depth (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ed, the positive anomaly).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe boreholes have almost no direct relation to the anomalies that appear in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ec and d and they are posted for comparison with the IMF1 and IMF2 maps (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ea and b).\u003c/p\u003e\n\u003cp\u003eAs mentioned earlier, the M-BEMD technique isolates the gravity anomalies according to their wavelengths, however, anomalies are normally of broadband wavelengths that can be separated into more than one IMF. Accordingly, we may notice that some anomalies exist in two IMF maps for example, the anomaly area outlined by the black box in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e. Additionally, the occurrence of geological structures, shown in IMF1, which are targets of hydrocarbon prospecting, refers to the tectonic stresses affecting the area including the sedimentary strata.\u003c/p\u003e"},{"header":"6. Conclusions","content":"\u003cp\u003eThe gravity field of the Southern Desert of Iraq has been analyzed into three residual fields and one regional utilizing the M-BEMD technique. These fields could be useful in assisting in the qualitative interpretation stage and could be linked with any quantitative geophysical work in the area. The three fields reflect different wavelength bands that may be classified into short-, intermediate-, and long- wavelength bands. Further, they could coincide with geological structures at shallow depths in the upper crust, upper basement surface relief (structures), and lithological variations in the deep basement terranes. The regional, however, may express the deeper part most likely at a depth level near the Moho. The positive anomalies in the short wavelength band map show a clear relation with the previously drilled hydrocarbon wells indicating good isolation for the geological structures and allowing for discovering new prospective hydrocarbon reservoirs. The map of anomalies in the intermediate band could reflect basement topography and show prospected regions of the distribution of basins/sub-basins. A broad nearly NS trending positive anomaly is a distinctive long band that could represent relatively high-density rocks of basic origin.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAcknowledgments\u003c/h2\u003e \u003cp\u003eWe would like to express our thanks to the Iraq Geological Survey (GEOSURV) for its role in providing the necessary data for this study.\u003c/p\u003e\n\u003cp\u003eCompeting interests: The authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAl-Bahadily HA, Al-Rahim AM, Long AJ (2022a) Postulated Precambrian Basement of the Iraq Southern Desert: A new look utilizing magnetic data. \u003cem\u003eMediterranean Geosciences Union Annual Meeting (MedGU-21)\u003c/em\u003e, Extended abstract (in press).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAl-Bahadily HA, Long AJ, Al-Rahim AM (2022b) Determination of Karst Terrane and Defining Deep Structure by Gravity, Southern Desert, Iraq. \u003cem\u003eMediterranean Geosciences Union Annual Meeting (MedGU-21)\u003c/em\u003e, Extended abstract no. 89 (in press).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAl-Kadhimi JAM, Fattah AS, Abbas MJ (1984) Unified Bouguer gravity data of Iraq, \u003cem\u003eGEOSURV Library\u003c/em\u003e, Baghdad, Iraq.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAl-Rahim AM (2016) Separating the gravity field of Iraq by using bidimensional empirical mode decomposition technique. 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Computers \u0026amp; Geosciences 36(7):987\u0026ndash;995.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKim D, Oh H-S (2009) EMD: a package for empirical mode decomposition and Hilbert spectrum. R Journal 1(1):40\u0026ndash;64.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJassim SZ \u0026ldquo;Late Precambrian development of Arabian Plate\u0026rdquo; Geology of Iraq. Edited by SZ Jassim and JC Goff (2006) Dolin, Prague, pp.\u0026nbsp;27\u0026ndash;31.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJassim SZ, Buday T \u0026ldquo;Tectonic Framework.\u0026rdquo; Geology of Iraq. Edited by SZ Jassim, JC Goff (2006) Dolin, Prague, pp.\u0026nbsp;45\u0026ndash;56.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMa\u0026rsquo;ala KhA (2009) Geology of Iraqi Southern Desert: Geomorphology. Iraqi Bull. Geol. Min. Special Issue:7\u0026ndash;33.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMelo FF, Barbosa Val\u0026eacute; CF (2020) Reliable Euler deconvolution estimates throughout the vertical derivatives of the total-field anomaly, Computers and Geosciences. 138, 10443.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMohammed SAG (2006) Megaseismic section across the northeastern slope of the Arabian Plate, Iraq. GeoArabia,11(4):77\u0026ndash;90.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSasikanth (2021) Bidimensional Emperical Mode Decomposition (BEMD) (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.mathworks.com/matlabcentral/fileexchange/28761-bi-dimensional-emperical-mode-decomposition-bemd\u003c/span\u003e\u003cspan address=\"https://www.mathworks.com/matlabcentral/fileexchange/28761-bi-dimensional-emperical-mode-decomposition-bemd\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e), MATLAB Central File Exchange. Retrieved July 23, 2021.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSissakian VK, Mahmoud AA, Awad AM (2013) Genesis and age determination of Al-Salman Depression, South Iraq. \u003cem\u003eIraqi Bulletin of Geology and Mining\u003c/em\u003e. 9 (1):1\u0026ndash;19.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTamar-Agha MY, Al-Sagri KhEA (2015) Shading further lights on the Upper Cretaceous \u0026ndash;Neogene subsurface lithostratigraphy of the Southwestern Iraq. Journal of Science, 56(1C):798\u0026ndash;827.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"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":"Southern Desert of Iraq, separation, geological structures, gravity interpretations","lastPublishedDoi":"10.21203/rs.3.rs-2849255/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-2849255/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe Southern Desert of Iraq covers a vast region in southwest Iraq. The stratigraphic column comprises relatively thick sedimentary strata, which overlay a Neoproterozoic basement and dip gently towards the northeast. The ground surface is depicted by intensive karst forms of variable dimensions, especially within carbonate rocks of the Dammam Formation (Middle-Upper Eocene). In the present study, we use the Bidimensional Empirical Mode Decomposition technique for analyzing the gravity field into multi-residual fields and one regional. Analyzing and interpreting the resultant fields utilizing the geological data are the aims of this study. A free download MATLAB code is applied to the gravity data of the Southern Desert which is designed to separate the two-dimensional gridded gravity map into three residual maps and a regional one. These maps may reflect depths at different levels; shallow, intermediate, deep, and near the Moho discontinuity, respectively. According to the available information about the geology of the area, the residual maps can be interpreted in terms of shallow-depth geological structures, which have an economic interest in hydrocarbon exploration, intra-basement structures, and variation in the density of the basement terranes. The regional map, however, is interpreted to be related to a deep-seated gravity source most likely near the Moho. Further, the results illustrate an obvious relation between some of the gravity positives, in the first residual map, and the drilled exploration wells. This suggests a delineation of newly prospected structural highs. In addition, the second residual map shows gravity negatives that probably delineate basement basins/sub-basins.\u003c/p\u003e","manuscriptTitle":"Analyzing the Gravity Field of the Southern Desert of Iraq with its Possible Geological Implications Using Multi-Bidimensional Empirical Mode Decomposition Technique","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-04-25 22:49:35","doi":"10.21203/rs.3.rs-2849255/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":"f74be059-8126-431e-9a6c-b6eef7188250","owner":[],"postedDate":"April 25th, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":20923365,"name":"Geophysics"}],"tags":[],"updatedAt":"2023-04-25T22:49:35+00:00","versionOfRecord":[],"versionCreatedAt":"2023-04-25 22:49:35","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-2849255","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-2849255","identity":"rs-2849255","version":["v1"]},"buildId":"J0_U0BvcaRcwD8yVFaRlm","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}