Petrological and Geotechnical Assessment of Siluro-Devonian Reef Complexes in the Peshawar Basin, Pakistan: Implications for Sustainable Resource and Geoheritage Management

Petrological and Geotechnical Assessment of Siluro-Devonian Reef Complexes in the Peshawar Basin, Pakistan: Implications for Sustainable Resource and Geoheritage Management | 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 Petrological and Geotechnical Assessment of Siluro-Devonian Reef Complexes in the Peshawar Basin, Pakistan: Implications for Sustainable Resource and Geoheritage Management Sayad Hussain, Khalid Latif, Waqas Ahmed, Biao Shu, Jehanzeb Khan, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7496598/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 02 Apr, 2026 Read the published version in Carbonates and Evaporites → Version 1 posted 13 You are reading this latest preprint version Abstract The Nowshera Reef and Ghundai Sar Formation of the Peshawar Basin, Pakistan, represent rare Siluro-Devonian reef complexes that preserve key transitions in Paleozoic carbonate platform evolution. This study provides the first integrated assessment of their petrography, diagenesis, and engineering properties to inform both geoheritage conservation and resource management. Field observations reveal fore-reef, reef-core, and back-reef facies hosting diverse fossils-honeycomb corals, stromatoporoids, crinoids, and graptolites-within limestones and dolostones affected by dolomitization, micritization, and cementation. Microscopic analysis confirms calcite-dominated fabrics with localized dolomitization, syntaxial overgrowths, and neomorphic textures. Mechanical testing shows moderately strong rock properties, with uniaxial compressive strength ranging from 19 to 58 MPa and tensile strength from 4 to 14 MPa. Nowshera Reef exhibits slightly higher strength and lower abrasion than the Ghundai Sar Formation, attributed to denser cementation and lower porosity. However, both formations exhibit strength and durability metrics comparable to other Silurian reefs globally, such as those in Estonia, where quarrying pressures have prompted preservation efforts. Despite moderate suitability as aggregate sources, the scientific value of these fossil-rich carbonates outweighs their economic use. Given ongoing degradation due to unregulated extraction, the study recommends prioritizing alternative lithologies for construction and formally designating these reef complexes as protected geoheritage sites. Peshawar Basin Silurian-Devonian Nowshera Formation Ghundai Sar Formation Engineering Properties Geoheritage Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1 Introduction The Siluro-Devonian reef complexes of the Peshawar Basin, Pakistan, are globally significant geoheritage sites that preserve an exceptional record of Paleozoic marine ecosystems and carbonate platform evolution. Nowshera reef (NR) is believed to be a unique instance of a complex reef deposit, covering all ideal morphological parts of a reef system (Mawson et al., 2003 ). These successions, particularly the Nowshera Reef and the Ghundai Sar Formation, capture the transition from microbial-dominated to metazoan-rich reef ecosystems, a pivotal interval in the history of marine biodiversity and Paleozoic carbonate platform development (James and Wood 2010). Regionally, they represent some of the few well-preserved Paleozoic reef complexes along the northern Gondwanan margin, offering critical insights into ancient reef-building processes and paleoenvironmental conditions within the Tethyan realm. The Nowshera Reef (NR) and Ghundai Sar Formation (GS) exhibit the facies of mature carbonate platforms, including fore-reef, reef-core, and back-reef deposits, along with reef breccias and fossiliferous limestones (Teichert and Stauffer 1965 ; Stauffer 1968 ; Khan 1969 ; Mawson et al. 2003 ). Their diverse fossil assemblages-corals, brachiopods, crinoids, and conodonts-enable precise biostratigraphic age constraints of Silurian to Early-Middle Devonian (Shah 2009 ; Talent and Mawson 1979 ) and suggest potential correlation with coeval limestones in Afghanistan, indicating regional continuity in reef development across northern Gondwana (Yaseen et al. 2019 ). These well-exposed outcrops thus constitute unparalleled natural laboratories for investigating reef evolution, paleoecology, and sedimentary dynamics. Despite their scientific and educational significance, these reefs face increasing threats from urbanization, infrastructure development, and uncontrolled quarrying for construction materials. Remote sensing and field observations over the past two decades document the progressive destruction of outcrops, eroding both their scientific value and geotourism potential. Early investigations provided only reconnaissance-level mapping, basic stratigraphy, and paleontological descriptions (Coulson 1936 ; Stauffer 1968 ; Barnett et al. 1966 ; Talent and Mawson 1979 ; Shah 2009 ), leaving major gaps in the understanding of their petrology, diagenetic evolution, and engineering behaviour (Price and De Freitas 1995 ; Tugrul and Gurpinar 1997 ). The described carbonate bodies represent the first Palaeozoic reefs discovered in Pakistan and contain a fossil fauna that is entirely new to Pakistan. Life changed so much during the Palaeozoic era that many of the organisms that lived during the later Palaeozoic were much closer to those of today. The available literature on the areas only manifests the stratigraphy of the siluro-devonian reef complexes, which lacks important of paleontological and diagenetic information and stratigraphic details of the Ghundai Sar formation are not well-documented and need further investigation. This study provides the first integrated geological, petrographic, and geotechnical assessment of the Nowshera Reef (NR) and Ghundai Sar Formation (GS). It characterizes the petrological and diagenetic features of the reefal carbonates and evaluates how these attributes influence their geotechnical behavior. The study further quantifies their mechanical properties through uniaxial compressive strength (UCS), uniaxial tensile strength (UTS), Los Angeles abrasion, and aggregate impact tests, and assesses their geotechnical suitability for construction applications, while recommending alternative aggregate sources to support geoheritage conservation. This integrated approach provides a foundation for balancing sustainable resource utilization with the preservation of Pakistan’s unique Siluro-Devonian reef complexes. 2 Geology of the Study Area 2.1 Systematic literature review Teichert and Stauffer (1965) contributed to the faunal description of the Siluro-Devonian rocks of the Nowshera area and reported them to belong to the Silurian-Devonian period. Based on conodonts evidence, a similar age was determined for these rocks by Barnett et al. (1966). However, the correlation and stratigraphy of different carbonates and clastic sediments created some uncertainty. The formation was later described in detail by Stauffer (1968) and by Ali and Anwar (1969), who interpreted these rocks as part of a Reefal complex. The current work offers significant of the target Silurian-Devonian reef complexes, it is primary outcome is the classification of these reefal complexes on the basis of outcrop-scale structure, an integrated approach-incorporating, meso-, and micro-level investigation will help biogenic components and diagenetic feature of the study area. Furthermore petrographical and geotechnical investigation of these reefs will facilitate regional comparison of aggregate and dimension stone resources with other formations. 2.2 Location and Basin Context The study area is situated in the Peshawar Basin of Khyber Pakhtunkhwa, northwestern Pakistan, along the northern margin of Gondwana. The Peshawar Basin is 8300 kilometers an intramontane depression bounded by the Main Boundary Thrust to the south and the Main Mantle Thrust to the north, and it preserves a thick Paleozoic to Cenozoic sedimentary succession (Pogue 1986; Kazmi and Jan 1997). Within this basin, the Nowshera Reef and the Ghundai Sar Formation represent two well-preserved Siluro-Devonian reef complexes (Fig. 1). These outcrops are among the few remaining Paleozoic reefal successions in the region and provide valuable records of early reef-building processes and shallow-marine depositional environments (Yaseen et al. 2019). Both the Ghundai Sar Formation and Nowshera Reef are dominated by calcite, dolomite, and abundant fossil fragments, reflecting complex depositional and diagenetic histories. Fig. 1 and Fig. 2 summarizes the spatial distribution of these reef complexes relative to major lithological units and fault systems in the Peshawar Basin. 2.3 Nowshera Reef The Nowshera Reef occurs about 3.5 km north of Nowshera city (34°01'44"N, 71°59'54"E) and extends laterally for approximately 20 km across isolated hills. It comprises fossiliferous limestone, dolomitic to marbleized limestone, calcareous quartzite, and minor argillite (Table 1). Stauffer (1968) subdivided the reef into a central reef-core unit and marginal reef breccias composed of fossil debris. These deposits form the youngest Paleozoic strata in this part of the basin and are unconformably overlain by the Jafar Kandao Formation near Swabi. Age interpretations, based on conodont and macrofossil assemblages, indicate an Early Devonian (Lochkovian) age (Talent and Mawson 1979; Shah 2009). Table 1 presents representative field photographs and (Fig. 2) lithological details of the Nowshera Formation. 2.4 Ghundai Sar Formation The Ghundai Sar Formation is located north of Jamrud Fort along the Warsak Canal and is similarly assigned a Siluro-Devonian age. The reef complex strikes east west and dips northward, forming a prominent isolated hill complex. Khan (1969) subdivided the formation into four lithological units: (i) grey to yellowish-grey dolomitized quartzite, (ii) talus and reef breccia, (iii) crinoidal limestone interbedded with phyllites, and (iv) a reef-core unit. These units collectively record dynamic shallow-marine depositional and diagenetic conditions during reef development. Table 2 present field photographs and lithological details of the Ghundai Sar Formation. 3 Methodology This study adopted a comprehensive methodology that integrated detailed field investigations with laboratory-based petrographic and geotechnical analyses. Fieldwork was carried out across the Siluro-Devonian reef complexes to document their structural, stratigraphic, and facies characteristics and to collect fresh, undeformed samples for subsequent testing. A total of 52 representative rock samples were collected from larger outcrops of the Nowshera Reef and Ghundai Sar Formation in the Peshawar Basin. Of these, 44 hand specimens (approximately 0.5 kg each) were designated for thin-section petrography, while larger bulk blocks, measuring 2-2.5 feet in length and 0.5-1 foot in thickness, were extracted for coring and mechanical testing. All samples were systematically labelled and transported to the National Centre of Excellence in Geology (NCEG), University of Peshawar, for further analyses. Field observations were conducted at both macro- and meso-scales. At the macro-scale, emphasis was placed on mapping large-scale structural features of the reef bodies, documenting their lateral continuity, and establishing stratigraphic relationships with adjacent lithologies. At the meso-scale, internal architectural features were examined, focusing on the constituents of the reef complexes, their vertical and lateral facies relationships, and other intermediate-scale characteristics that could influence mechanical behaviour. These observations were used to guide the sampling strategy and provided the contextual framework for laboratory interpretations. Laboratory investigations were divided into petrographic and geotechnical components, for Petrographic analysis preparation of thin sections from 52 samples for microscopic study, which were examined under a Nikon LV100ND Polarizing Microscope at NCEG to determine mineralogy, textural attributes, porosity types, and diagenetic features such as dolomitization, cementation, and recrystallization. For geotechnical testing, 14 cores were drilled from the bulk blocks using a Universal Coring drill Machine, including six cores (GS1-GS6) from the Ghundai Sar Formation and eight cores (NR1-NR8) from the Nowshera Reef (Fig. 5 ). Physical property tests, including water absorption, specific gravity, and porosity measurements, were performed on the cores sample, followed by mechanical strength tests such as uniaxial compressive strength (UCS) and uniaxial tensile strength (UTS). Additionally, Los Angeles Abrasion (LAA) and Aggregate Impact Value (AIV) tests were conducted to evaluate aggregate durability. All sample preparation and testing procedures strictly adhered to ASTM International standards (1971, 1986, 2006, 2009, 2016). Field observations, petrographic results, and geotechnical data were integrated to interpret the diagenetic history and engineering properties of the studied reef complexes. This combined dataset allowed for the establishment of robust correlations between depositional fabrics, diagenetic modifications, and the mechanical performance of the carbonate rocks. The results of these analyses, along with their implications for dimension stone and aggregate resource potential, are presented in the subsequent sections of this manuscript. 4 Results 4.1 Macroscopic Analysis The Ghundai Sar Formation and Nowshera Reef exhibit pronounced diagenetic alterations, including dolomitization, neomorphism, cementation, micritization, dissolution, and compaction, which have modified the original depositional fabrics. Both formations are primarily composed of limestone, dolomite, and subordinate quartzite, and host a diverse suite of fossils such as corals, crinoids, stromatoporoids, graptolites, bryozoans, gastropods, and cephalopods (Fig. 3 ). Fossilized honeycomb corals (favositids) are particularly abundant in the Ghundai Sar Formation and indicate a middle Silurian to lower Devonian age, while the occurrence of graptolites with variable branching morphologies suggests deposition in relatively deeper fore-reef settings. Crinoids, represented by stem fragments and isolated ossicles, are common in both formations and reflect periodic reefal environmental conditions. Stromatoporoids, preserved in the Nowshera Reef, are laminated calcified sponges that served as major reef-building organisms during the Middle Ordovician to Late Devonian and are characterized by well-developed laminae, pillars, and galleries (Fig. 3 ). Other faunal elements include coiled gastropods and cephalopods, bryozoans forming delicate colonial frameworks, and mollusks with diverse shell morphologies (Fig. 3 ). These fossil assemblages provide important paleoecological information on the zonation of ancient reef ecosystems, with stromatoporoids and corals dominating reef-core facies and crinoids and graptolites being more prevalent in deeper fore-reef environments. 4.2 Microscopic Analysis Petrographic analysis shows that the reef complexes are dominated by coarse-grained calcite and dolomite (Fig. 4 ). Calcite occurs as anhedral to subhedral crystals with characteristic rhombohedral cleavage and pearly-gray interference colors under cross-polarized light, while dolomite appears as both primary grains and secondary replacement phases displaying perfect rhombohedral cleavage. Extensive micritization is evident, with algal-bored grains enclosed by micritic envelopes indicative of shallow marine phreatic conditions. Dissolution features are common in shoal and foreshore facies, generating secondary porosity through selective leaching of unstable grains. Cementation occurs in multiple forms, including syntaxial overgrowths on echinoderm fragments, granular and drusy mosaic cements, and late-stage blocky calcite cements that occlude remaining pore spaces. Neomorphic recrystallization and dolomitization locally obscure primary textures, forming mosaics ranging from microcrystalline to coarsely crystalline dolomite. Microfacies analysis demonstrates clear relationships between depositional environment, fossil assemblages, and diagenetic overprint. Reef-core facies display the highest biological framework development and marine cementation, whereas back-reef and lagoonal deposits exhibit stronger evidence of meteoric diagenesis. These petrographic characteristics, combined with the fossil assemblages, indicate the complex interplay of biological, sedimentological, and diagenetic processes that shaped the present-day fabrics of the studied carbonate rocks. 4.3 Geotechnical Properties Geotechnical testing reveals distinct contrasts between the Ghundai Sar Formation (GS) and the Nowshera Reef (NR) in porosity, strength, and durability (Table 3 ). Water absorption and porosity are consistently low in GS (0.08–0.14% and 0.21–0.38%), reflecting its dense, uniform fabric, whereas NR exhibits slightly higher and more variable values (0.10–0.33% and 0.29–0.93%). Both formations have specific gravity values above 2.73, with NR reaching 2.86, confirming their suitability for structural and dimension stone use. Uniaxial compressive strength (UCS) according with (ASTM: D2938–95) ranges from 19.8–35.9 MPa in GS and 19.1–58.2 MPa in NR, with the highest values in NR5 and NR6. Uniaxial tensile strength (UTS) (ASTM: D3967–16) shows a similar trend: GS ranges 3.84–13.26 MPa, while NR reaches 5.51–13.85 MPa. These results indicate that NR locally attains higher strength due to better cementation and partial dolomitization. Durability indices confirm moderate wear resistance. Los Angeles abrasion (LAA) and Aggregate Impact Values (AIV) are 27-27.2% and 24.3-24.76% for GS, versus 23.1–23.3% and 21.02–22.4% for NR, indicating that NR is slightly more resistant to mechanical wear. These findings suggest both formations are technically suitable for construction applications, with NR providing occasional high-strength blocks appropriate for dimension stone. Property distributions and formation variability are illustrated in Fig. 6 A-I. Table 3 Summary of geotechnical properties of the Ghundai Sar Formation and Nowshera Reef. Formation Sample UCS(Mpa) UTS(Mpa) LAA(%) AIV(%) WA(%) SG(g/cm³) n (%) D2938-95 D3967-16 C131-14 C125 C97-02 C830-00 GS1 27.4 7.93 0.08 2.730 0.22 GS2 25.0 13.26 0.08 2.730 0.21 GS3 25.0 9.32 0.13 2.735 0.34 Ghundai Sar GS4 19.8 6.51 0.12 2.736 0.32 GS5 32.6 7.50 0.08 2.736 0.21 GS6 35.9 3.84 0.14 2.787 0.38 Average Min-Max 27.62 19.8–35.9 8.06 3.84–13.26 27-27.2% 24.3-24.76% 0.105 0.08–0.14 2.742 2.730–2.787 0.28 0.21–0.38 NR1 32.5 12.86 0.17 2.847 0.49 NR2 19.1 13.85 0.18 2.848 0.50 NR3 32.0 10.22 0.33 2.834 0.93 Nowshera Reef NR4 34.2 8.17 0.31 2.847 0.88 NR5 58.2 8.48 0.18 2.809 0.51 NR6 49.0 5.51 0.2 2.856 0.56 NR7 36.4 9.32 0.1 2.788 0.29 NR8 25.5 10.54 0.17 2.858 0.48 Average Min-Max 35.86 19.1–58.2 9.86 5.51–13.85 23.1–23.3% 21.02–22.4% 0.205 0.10–0.33 2.835 2.788–2.858 0.58 0.29–0.93 WA = water absorption; Gs = specific gravity; n = porosity; UCS = uniaxial compressive strength; UTS = uniaxial tensile strength; LAA = Los Angeles abrasion; AIV = aggregate impact value. 5 Discussion Petrographic and physico-mechanical analysis indicates that the Ghundai Sar Formation (GS) and Nowshera Reef (NR) are medium- to coarse-grained carbonate rocks composed primarily of calcite and dolomite. Under plane-polarized light, calcite appears mostly anhedral to subhedral with cloudy to clear textures, low to moderate relief, and rhombohedral cleavage. Dolomite occurs as high-relief, fine- to coarse-grained colorless crystals with perfect rhombohedral cleavage. Both formations exhibit pervasive diagenetic overprinting, including micritization, dissolution, cementation, neomorphism, and localized dolomitization-features that influence porosity and mechanical performance. Void-filling cements manifest as syntaxial overgrowths, granular mosaics, and coarse blocky calcite, often enhancing fabric strength through pore occlusion. Fossil assemblages include honeycomb corals (favositids), crinoids, stromatoporoids, graptolites, bryozoans, gastropods, and cephalopods, with their distribution reflecting reef zonation. Stromatoporoids and corals dominate reef core facies, while crinoids and graptolites are more common in fore-reef and back-reef environments. These faunal assemblages confirm the Siluro-Devonian age and add substantial scientific value, warranting geoheritage designation. The depositional environment of the Nowshera Reef and Ghundai Sar Formation are interpreated as a shallow marine reefal system and an outer-shelf to basinal system, respectively (Stauffer, 1968 ; Khan et al.,1989), interpretive diagram of depositional environments is shown in Fig. 6 , (this study; modified after Wilson, 1975 ; James and Kendall, 1992 ). The fossils of Nowshera reef, stromatolites highlight both biological activity and open marine connection, the depositional setting reflect a shallow, tropical carbonates reef system influenced by both biological construction and early diagenesis. The Ghundai Sar formation therefore represent a carbonates outer shelf slope basinal system, where the presence of graptolite confirms depostion in open marine condition with connection to deeper basins. The formations are classified as moderately strong (ISRM 1981), with NR exhibiting higher UCS (mean: 35.9 MPa; peak: 58.2 MPa) and UTS (9.9 MPa) than GS (UCS: 27.6 MPa; UTS: 8.1 MPa). Durability indices such as Los Angeles abrasion (NR: 23.3%; GS: 27.2%) and impact value (NR: 21.0; GS: 24.8%) show that both satisfy general construction specifications, though NR offers better performance. Specific gravity values of 2.835 g/cm³ for NR and 2.742 g/cm³ for GS further reflect denser fabrics in NR. However, field observations during sample preparation revealed flaky and elongated fragments in both formations, suggesting potential issues with particle shape that could affect performance as high-grade aggregate. 5.1 Relationships Between Petrography and Physico-Mechanical Properties Mechanical behavior correlates closely with petrographic attributes. Denser fabrics-marked by micritic envelopes, tight cementation, and dolomitized zones-tend to yield higher UCS and UTS values. Scatter plots (Fig. 7 A-C) illustrate negative correlations between UCS and both porosity and water absorption, while a positive correlation exists between UCS and UTS. Bar charts and boxplots (Fig. 7 D-I) confirm that NR has a broader range in UCS and porosity than GS, reflecting lithofacies heterogeneity. Statistical testing shows that UCS in NR is about 30% higher than in GS. A two-sample t-test (t = 1.65, p = 0.1293) indicates that this difference is not statistically significant at the 95% confidence level. Similarly, UTS values are higher in NR (9.87 MPa vs. 8.06 MPa; t = 1.11, p = 0.2818) but again not significant. In contrast, porosity differences are statistically significant (NR mean: 0.58%; GS: 0.28%; t = 3.47, p = 0.0052), attributed to fossil dissolution and secondary porosity in NR’s heterogeneous facies. Dense boundstone fabrics in reef-core samples (e.g., NR5) yield UCS values above 50 MPa, while GS consists largely of uniform micritic to packstone textures with moderate sparry cementation and minimal dolomitization, yielding UCS ~ 25–35 MPa. These trends are consistent with carbonate literature, where diagenetic evolution, cementation, and fabric control strength and durability (Choquette and Pray 1970; Shakoor and Bonelli 1991 ; Bell 2007 ; Lucia 2007; Baechle et al. 2008). Even where direct linear correlations are weak, facies-based differences emphasize the predictive value of microstructural interpretation in geomechanical behaviour and resource evaluation. 5.2 Geotechnical Suitability and Conservation Both GS and NR are mechanically serviceable as construction aggregates, yet they are not optimal when compared to other regional carbonate formations. Table 4 shows that the Kohat (KF) and Shekhan (SF) formations outperform NR and GS with higher UCS (> 39 MPa), lower abrasion and impact values (≈ 20% and 11–16%, respectively), and comparable porosity and absorption. While NR and GS meet general specifications, their mechanical variability and visual degradation (flaky fragments) raise concerns for high-performance use. From a conservation perspective, NR and GS are exceptional fossiliferous reef complexes with complete reef-core, fore-reef, and back-reef facies preserved. Field observations and Landsat imagery (2005–2022) reveal ongoing excavation and reef depletion (Fig. 8 ), posing imminent risk to this rare geological archive. As global awareness of fossil reef preservation grows, it is recommended that mining be redirected toward mechanically superior but geologically less significant formations such as KF and SF. This dual strategy supports both sustainable development and preservation of Pakistan’s mid-Paleozoic geological heritage Table 4 Comparison of Geotechnical properties of ccurrent study with previous studies Geotechnical Properties This Study (GS) (NR) Asif et al. 2022 (WL) (SF) (KF) Sarfaraz et al. 2021 (MF) (ML) Ullah et al. 2020 (LL) (SH) (SSF) Rehman et al. 2020 (SSF) (KW) Anjum et al. 2018 (KL) Naeem et al. 2014 (ML) (KW) LAA(%) 27.2 23.3 23.37 22.90 19.99 25.12 16.93 23.88–24.38 14.08–16.53 14.81–16.92 27.10 20.86 26.65 23.93–25.12 14.93–15.85 AIV(%) 24.76 21.02 16.80 14.80 14.48 20.75 22.03 13.70–15.37 11.80–14.90 11.38–12.08 14.09 14.89 _ - 15.36–16.01 11.40–12.71 UCS(MPa) 27.62 35.86 - 93.35 69.31 - - - - - - - 19.86–39.08 - - UTS (MPa) 8.06 9.86 - - - - - - - - - - - - - WA(%) 0.105 0.205 0.48 0.72 0.64 0.65 0.68 0.98–1.36 0.25–0.58 0.38–1.04 0.81 0.89 0.68 0.94–1.61 0.60–0.69 SG (g/cm³) 2.74 2.83 2.70 2.70 2.71 2.76 2.63 2.70–2.78 2.60–2.64 2.61–2.66 2.68 2.73 2.72 2.60–2.63 2.72–2.77 n (%) 0.28 0.58 - 2.43 2.43 - - 2.33–2.69 1.14–1.44 1.04–1.61 - - - 2.31–2.98 1.76–2.12 GS = Ghundai Sar Formation; NR = Nowshera Reef; WL = Wargal limestone; SF = Shekhan Formation; KF = Kohat Formation; MF = Muzaffarabad formation; ML = Margalla Hill limestone; LL = Lockhart limestone; SH = Shekhai Formation; SSF = Samana Suk Formation; KW = Kawagarh Formation; KL = Khyber limestone. Geotechnical properties: LAA = Los Angeles abrasion; AIV = Aggregate impact value; UCS = Uniaxial compressive strength; UTS = Uniaxial (Brazilian) tensile strength; WA = Water absorption; SG = Specific gravity; n = Aggregate porosity. 5.3 Global Context: Comparison with Silurian-Devonian Reef Complexes The Paleozoic reef complexes in Pakistan host a rich and diverse fossil fauna, with ages constrained to the Silurian-Early Middle Devonian based on biostratigraphic evidence (Shah 2009 ; Talent and Mawson 1979 ). Their faunal composition suggests possible correlation with coeval Paleozoic limestones in Afghanistan, indicating broader regional continuity in reef development along the northern Gondwanan margin. The geological and mechanical characteristics of NR and GS align with mid-Paleozoic reef systems globally. In the Canning Basin (Western Australia), reef-core limestones exhibit early cementation and porosity occlusion similar to NR, while dolomitized back-reef zones show increased heterogeneity in porosity and strength. Banks Island reefs (Arctic Canada) also consist of low-porosity, tightly cemented limestones, with weaker zones linked to fossil abundance and fracturing. In the U.S. Midwest, Silurian reef complexes such as Thornton Reef were initially exploited as aggregate sources but later designated as geoheritage sites due to their paleontological significance (Mikulic and Kluessendorf 2023). These reefs showed mechanical heterogeneity, with dolomitized portions being more suitable for construction use. Similarly, Saaremaa Island in Estonia has proposed legal protection for Silurian reef cliffs with unique fossil content (Vinn et al., 2024 ). Lithuanian Silurian reef studies further emphasize the limitations of such diagenetically hardened limestones for reservoir or engineering purposes due to low matrix porosity (Kaminskaite-Baranauskiene et al. 2024 ). These global analogues demonstrate a consistent pattern: Silurian-Devonian reefs are mechanically heterogeneous, diagenetically altered, and of high scientific value. As such, international best practices increasingly promote geoheritage designation and restrict quarrying in such formations an approach also recommended here for the NR and GS reef systems. 6 Conclusions This study presents the first integrated petrographic and geotechnical characterization of the Siluro-Devonian reef complexes of the Peshawar Basin, focusing on the Nowshera Reef (NR) and Ghundai Sar Formation (GS). The study has several conclusions. First, these reefal limestones, dominated by calcite and dolomite with distinct facies architectures and diagenetic overprints (micritization, dolomitization, and cementation), preserve a rich Siluro-Devonian fossil assemblage including stromatoporoids, honeycomb corals, bryozoans, and crinoids. The Nowshera Reef is one of the few intact mid-Paleozoic reef systems on the northern Gondwanan margin. The study documents facies-specific variation in diagenetic textures and early cementation, offering rare paleoenvironmental insights from Pakistan. Second, mechanical characterization revealed that NR exhibits higher strength and porosity variability (UCS: 19–58 MPa, avg. 35.9 MPa; porosity up to 0.93%) than GS (UCS: 19.8–35.9 MPa, avg. 27.6 MPa; porosity up to 0.38%). The mean UCS of NR is ~ 30% higher than GS, a difference that is not statistically significant (p = 0.1293) but consistent with petrographic evidence of greater cementation and dolomite content. These results align with international data on Silurian-Devonian reefs, which often show moderate strength and fabric-controlled heterogeneity (e.g., Canning Basin, Banks Island, Illinois Thornton Reef). The flaky particle shape and moderate abrasion resistance (LAA ~ 23–27%) limit their utility for high-performance construction applications. Third, while the geotechnical properties of NR and GS meet general construction standards, they are not exceptional. Comparisons with younger Pakistani formations (e.g., Kohat and Shekhan formations with UCS > 39 MPa) indicate that stronger, more durable aggregate alternatives exist. This supports the argument that quarrying these globally significant reefs for average-quality aggregate is scientifically unsound. Fourth, landsat imagery (2005–2022) and field observations reveal accelerating degradation of reef outcrops from unregulated extraction. Given their fossil richness, paleoenvironmental importance, and rarity, NR and GS merit formal geoheritage designation. Their conservation would align Pakistan with global best practices (e.g., protection of Silurian reefs in Estonia and USA) and fill a national void in formally recognized geoheritage sites. Fifth, this study offers a replicable model for evaluating geologically significant sites facing extraction pressures. By combining petrographic, mechanical, and sustainability analyses, it demonstrates how to inform conservation policy with empirical data. The dataset is also relevant to researchers studying carbonate reservoir analogues or Paleozoic reef evolution globally. 7 Recommendations NR and GS should be nominated for national geoheritage status to ensure long-term preservation, supported by educational and legislative outreach. Prioritize the use of Kohat, Shekhan, and Margalla Hill formations as construction aggregates, given their superior mechanical properties and lower heritage value. Implement zoning regulations and incentives to steer construction projects away from geoheritage site Declarations Competing Interests The authors declare no competing financial or non-financial interests related to this work. Author Contribution All authors have equally contributions. Acknowledgement The authors gratefully acknowledge the National Centre of Excellence in Geology (NCEG), University of Peshawar, for providing funding and laboratory facilities. References Anjum MN, Ali N, Rehman ZU, Ghayas M, Ahmad W (2018) Rock aggregate potential of the limestone units in the Khyber Formation, Khyber ranges, Pakistan. Int J Econ Environ Geol 9(4):15–22 Asif AR, Islam L, Ahmed W, Sajid M, Qadir A, Ditta A (2022) Exploring the potential of Eocene carbonates through petrographic, geochemical, and geotechnical analyses for the utilization as aggregate for engineering structure. Arab J Geosci 15:1105. [https://doi.org/10.1007/s12517-022-10115-2] Ali, KA, Anwar, J (1969) Stratigraphic studies of the Nowshera reef complex, Nowshera Tehsil, West Pakistan. Geol Bull Univ Peshawar 4:33-43 ASTM (1971) D-2938. Standard test method for unconfined compressive strength of intact rock core specimens. American Society for Testing and Materials, Philadelphia, Pennsylvania, USA ASTM (1986) D-3976. Standard test method for splitting tensile strength of intact rock core specimens. American Society for Testing and Materials, Philadelphia, Pennsylvania, USA ASTM (2006) C-131. Standard test method for resistance to degradation of small-size coarse aggregate by abrasion and impact in the Los Angeles Machine. American Society for Testing and Materials ASTM (2009) C-97. Standard test methods for absorption and bulk specific gravity of dimension stone. American Society for Testing and Materials ASTM (2016) C-830. Standard test methods for apparent porosity, liquid absorption, apparent specific gravity, and bulk density of refractory shapes by vacuum pressure. American Society for Testing and Materials Barnett SG, Kohut JJ, Rust CC, Sweet WC (1966) Conodonts from Nowshera Reef limestone (uppermost Silurian or lowermost Devonian) West Pakistan. J Paleontol 40:435–438 Bell FG (2007) Engineering geology, 2nd edn. Butterworth-Heinemann, Oxford Coulson AL (1936) Marble of the North-West Frontier Province. Rec Geol Surv India 3:328–344 D’Andrea DV, Fischer RL, Fogelson DE (1965) Prediction of compressive strength of rock from other properties. US Bur Mines Rep Invest 6702 ISRM (International Society for Rock Mechanics) (1981) Rock characterization, testing and monitoring. In: Brown ET (ed) ISRM suggested methods. Pergamon, Oxford James, NP, Kendall AC (1992) Introduction to carbonate and evaporite facies models. In Walker RG, James (Eds) Facies models: Response to sea level change. Geological Association o Canada Kaminskaite-Baranauskiene I, Cichon-Pupienis A, Makauskas P (2024) Silurian barrier reef in Lithuania: Reservoir properties and low enthalpy geothermal heat potential. Heliyon 10(4)\:e26360. [https://doi.org/10.1016/j.heliyon.2024.e26360] Kazmi AH, Jan MQ (1997) Geology and tectonics of Pakistan. Graphic Publishers, Karachi, 554 p Khan MA (1969) Siluro-Devonian Reef Complex of Ghundai Sar and vicinity, Jamrud, Khyber Agency. Geol Bull Univ Peshawar 4:33–43 Khan SR, Kakar DM, Jan MR, Din M, Ahmed I (1989) Stratigraphy and structure of the Peshawar basin, Pakistan. Geol Bull Univ Peshawar, 22(1), 1-15 Mawson R, Talent JA, Molloy P, Simpson AJ (2003) Siluro-Devonian (Pridoli–Lochkovian and early Emsian) conodonts from the Nowshera area, Pakistan: implications for the mid-Palaeozoic stratigraphy of the Peshawar Basin. Courier Forsch Senckenberg 245:83–105 Mikulic DG, Kluessendorf J (2024) Geoheritage and geoconservation in the American Midwest: Silurian reefs of the Milwaukee–Chicago region. In: Clary RM, Pyle EJ, Andrews WM (eds) Geology’s significant sites and their contributions to geoheritage. Geological Society, London, Special Publications, 543:135–148. [https://doi.org/10.1144/SP543-2023-51] Naeem M, Khalid P, Sanaullah M, Din ZU (2014) Physio-mechanical and aggregate properties of limestones from Pakistan. Acta Geod Geophys 49:369–380. [https://doi.org/10.1007/s40328-014-0054-8] Pogue KR, Hussain A (1986) New light on stratigraphy of Nowshera area and the discovery of early to middle Ordovician trace fossils in NWFP Pakistan. Geol Surv Pak Inf Release 135:15 Price DG, De Freitas MH (1995) Engineering geology: principles and practices. Springer-Verlag, Berlin Heidelberg Rehman G, Zhang G, Rahman MU, Rahman NU, Usman T, Imraz M (2020) The engineering assessments and potential aggregate analysis of Mesozoic carbonates of Kohat Hills range, KP, Pakistan. Acta Geod Geophys 55:477–493. [https://doi.org/10.1007/s40328-020-00301-9] Sarfraz Y, Basharat M, Riaz MT, Khan MA, Shahzad A, Ahmed KS (2021) Evaluation of physicomechanical properties of crushed rock aggregates: a case study from the Sub-Himalaya, Pakistan. Acta Montan Slovaca 26(3):375–384. [https://doi.org/10.46544/AMS.v26i3.07] Shah SMI (2009) Stratigraphy of Pakistan. Mem Geol Surv Pak 12:138 Shakoor A, Bonelli RE (1991) Relationship between petrographic characteristics, engineering index properties, and mechanical properties of selected sandstones. Bull Int Assoc Eng Geol 1:55–71. [https://doi.org/10.1007/BF02590228] Stauffer KW (1968) Siluro-Devonian Reef complex near Nowshera, West Pakistan. Geol Soc Am Bull 79:1131–1350. [https://doi.org/10.1130/0016-7606(1968)79\[1131\:SRcNW\]2.0.CO;2] Talent JA, Mawson R (1979) Paleozoic–Mesozoic biostratigraphy of Pakistan in relation to biogeography and the coalescence of Asia. In: Farah A, DeJong KA (eds) Geodynamics of Pakistan. Geological Survey of Pakistan, Quetta, pp 81–102 Teichert C, Stauffer KW (1965) Paleozoic reef discovery in Pakistan. Geol Surv Pak 14:3 Tugrul A, Gurpinar O (1997) The effect of chemical weathering on the engineering properties of Eocene basalts in north-eastern Turkey. Environ Eng Geosci 3:225–234. [https://doi.org/10.2113/gseegeosci.3.2.225] Ullah R, Ullah S, Rehman N, Ali F, Asim M, Tahir M, Ullah S, Muhammad S (2020) Aggregate suitability of the Late Permian Wargal Limestone at Kafar Kot Chashma Area, Khisor Range, Pakistan. Int J Econ Environ Geol 11(1):89–94. [https://doi.org/10.46660/ijeeg.Vol11.Iss1.2020.418] Vinn O, Wilson MA, Isakar M, Toom U (2024) Two high value geoheritage sites on Sõrve Peninsula (Saaremaa Island, Estonia): a window to the unique Late Silurian fauna. Geoheritage 16(2):53–68. [https://doi.org/10.1007/s12371-024-00957-7] Wilson JL (1975) Carbonate facies in geologic history. Springer-Verlag, Berlin Yaseen M, Mukhtiar G, Muhammad NA, Sajid M, Irfan Ullah J, Mubbashir M, Emad Ullah, Waqas M (2019) A Novel Approach to Evaluate, Highlight, and Conserve the Geologically Significant Geoheritage Sites from the Peshawar Basin, Khyber Pakhtunkhwa, Pakistan: Insights into Their Geoscientific, Educational, and Social Importance. Geoheritage 4:1461-1474. Tables Table 1 and 2 are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files Table1and2.docx Cite Share Download PDF Status: Published Journal Publication published 02 Apr, 2026 Read the published version in Carbonates and Evaporites → Version 1 posted Editorial decision: Revision requested 19 Nov, 2025 Reviews received at journal 13 Nov, 2025 Reviews received at journal 12 Nov, 2025 Reviews received at journal 10 Nov, 2025 Reviewers agreed at journal 30 Oct, 2025 Reviewers agreed at journal 30 Oct, 2025 Reviewers agreed at journal 29 Oct, 2025 Reviews received at journal 22 Sep, 2025 Reviewers agreed at journal 21 Sep, 2025 Reviewers invited by journal 09 Sep, 2025 Editor assigned by journal 09 Sep, 2025 Submission checks completed at journal 01 Sep, 2025 First submitted to journal 30 Aug, 2025 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. 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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-7496598","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":514420243,"identity":"2c651e9c-6f17-4289-ae00-a4d0dfa0ead8","order_by":0,"name":"Sayad Hussain","email":"","orcid":"","institution":"Central South University","correspondingAuthor":false,"prefix":"","firstName":"Sayad","middleName":"","lastName":"Hussain","suffix":""},{"id":514420245,"identity":"97bfc1c2-b1b6-4107-b81a-eef5cb7a1d6b","order_by":1,"name":"Khalid Latif","email":"","orcid":"","institution":"University of 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Ullah","lastName":"Hashmi","suffix":""},{"id":514420255,"identity":"84c610a4-7b84-4c4d-ae24-1ff544edd335","order_by":7,"name":"Zakir Ullah","email":"","orcid":"","institution":"University of Peshawar","correspondingAuthor":false,"prefix":"","firstName":"Zakir","middleName":"","lastName":"Ullah","suffix":""}],"badges":[],"createdAt":"2025-08-30 16:53:20","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7496598/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7496598/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s13146-026-01262-w","type":"published","date":"2026-04-02T15:58:14+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":91538753,"identity":"8268c71d-1076-4500-9e6b-788e96d6bec4","added_by":"auto","created_at":"2025-09-17 13:34:32","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":646488,"visible":true,"origin":"","legend":"\u003cp\u003eGeological Map of the northwest Pakistan illustrating the distribution of major lithological unit, reef complex, rocks units and fault system, (modified after Ahmad et al. 2013).\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7496598/v1/67c593aec90cf1205f44f8d6.png"},{"id":91538751,"identity":"a9016e43-58c7-4d6f-a6be-89d4bf15ba65","added_by":"auto","created_at":"2025-09-17 13:34:32","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":550534,"visible":true,"origin":"","legend":"\u003cp\u003e(A) History of stratigraphic columns nomenclature for the eastern Peshawar basin, northern Pakistan: (B) correlation of composite stratigraphic columns for a selected area of the Piggyback basins (modified after Pogue and Hussain, 1986).\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7496598/v1/eef6c4b47574855a644ca879.png"},{"id":91538752,"identity":"9ae0abad-0a76-48f1-aa75-5460a06ffeca","added_by":"auto","created_at":"2025-09-17 13:34:32","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1656784,"visible":true,"origin":"","legend":"\u003cp\u003eField photographs showing representative fossiliferous textures from the Nowshera Reef and Honeycombs coral from Ghundai Sar.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-7496598/v1/6bf79b30eab36b173d9b4fd1.png"},{"id":91539913,"identity":"a5bba705-8340-4c76-ad3b-8a23107987e5","added_by":"auto","created_at":"2025-09-17 13:42:32","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1792193,"visible":true,"origin":"","legend":"\u003cp\u003ePetrographic features of the Ghundai Sar Formation (GS) and Nowshera Reef (NR).\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-7496598/v1/6e0f67a73032ee3d92c12a22.png"},{"id":91538755,"identity":"a0956bfe-ec13-4251-b57e-cec8e94e0b58","added_by":"auto","created_at":"2025-09-17 13:34:32","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1115853,"visible":true,"origin":"","legend":"\u003cp\u003e(A) Bulk sample under core drilling machine; (B,D\u0026amp;C,E) core samples of Ghundai Sar and Nowshera reef for UCS; (F,H\u0026amp;G,I) core samples of Ghundai Sar and Nowshera Reef for UTS before and after loading.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-7496598/v1/4153a04d6175666fc464b043.png"},{"id":91538764,"identity":"c85144f5-63e3-4d40-9333-c091e2b48420","added_by":"auto","created_at":"2025-09-17 13:34:32","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":1003969,"visible":true,"origin":"","legend":"\u003cp\u003eDraw a depositional environment of the Ghundai Sar and Nowshera Reef based on literature, where NR represent shallow marine, while GS reflect an outer shelf to deep marine.\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-7496598/v1/a8ee5471368483614bde2b51.png"},{"id":91538757,"identity":"9a744798-f4f0-484e-b831-e1eb3fca44d5","added_by":"auto","created_at":"2025-09-17 13:34:32","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":122406,"visible":true,"origin":"","legend":"\u003cp\u003eGeotechnical properties of the Ghundai Sar Formation (GS, blue) and Nowshera Reef (NR, orange): (A-C) Scatter plots of UCS vs. porosity, water absorption, and UTS; (D-E) Bar charts of LAA and AIV; (F-I) Boxplots of UCS, UTS, porosity, and water absorption.\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-7496598/v1/d909d5882903d93240611f47.png"},{"id":91539914,"identity":"f9d49818-ed64-44a0-b70f-4b514f643faf","added_by":"auto","created_at":"2025-09-17 13:42:32","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":1929609,"visible":true,"origin":"","legend":"\u003cp\u003eSeries of Landsatimages (yellow line show excavation from 2005 to 2022), while right side images show quarrying of the Nowshera Reef.\u003c/p\u003e","description":"","filename":"floatimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-7496598/v1/31834558bb2633085ec419e2.png"},{"id":106344363,"identity":"44b138a7-25ac-4faf-902b-7b183fee8307","added_by":"auto","created_at":"2026-04-07 16:13:50","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":9441049,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7496598/v1/71e24c8f-586e-4477-be8e-3feefdeb335c.pdf"},{"id":91538758,"identity":"914c1849-5e13-4cc5-97a6-63d7db0db898","added_by":"auto","created_at":"2025-09-17 13:34:32","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":2789612,"visible":true,"origin":"","legend":"","description":"","filename":"Table1and2.docx","url":"https://assets-eu.researchsquare.com/files/rs-7496598/v1/ae02fb65bea139699f002cd7.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Petrological and Geotechnical Assessment of Siluro-Devonian Reef Complexes in the Peshawar Basin, Pakistan: Implications for Sustainable Resource and Geoheritage Management","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eThe Siluro-Devonian reef complexes of the Peshawar Basin, Pakistan, are globally significant geoheritage sites that preserve an exceptional record of Paleozoic marine ecosystems and carbonate platform evolution. Nowshera reef (NR) is believed to be a unique instance of a complex reef deposit, covering all ideal morphological parts of a reef system (Mawson et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). These successions, particularly the Nowshera Reef and the Ghundai Sar Formation, capture the transition from microbial-dominated to metazoan-rich reef ecosystems, a pivotal interval in the history of marine biodiversity and Paleozoic carbonate platform development (James and Wood 2010). Regionally, they represent some of the few well-preserved Paleozoic reef complexes along the northern Gondwanan margin, offering critical insights into ancient reef-building processes and paleoenvironmental conditions within the Tethyan realm.\u003c/p\u003e\u003cp\u003eThe Nowshera Reef (NR) and Ghundai Sar Formation (GS) exhibit the facies of mature carbonate platforms, including fore-reef, reef-core, and back-reef deposits, along with reef breccias and fossiliferous limestones (Teichert and Stauffer \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e1965\u003c/span\u003e; Stauffer \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e1968\u003c/span\u003e; Khan \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1969\u003c/span\u003e; Mawson et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). Their diverse fossil assemblages-corals, brachiopods, crinoids, and conodonts-enable precise biostratigraphic age constraints of Silurian to Early-Middle Devonian (Shah \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Talent and Mawson \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e1979\u003c/span\u003e) and suggest potential correlation with coeval limestones in Afghanistan, indicating regional continuity in reef development across northern Gondwana (Yaseen et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). These well-exposed outcrops thus constitute unparalleled natural laboratories for investigating reef evolution, paleoecology, and sedimentary dynamics.\u003c/p\u003e\u003cp\u003eDespite their scientific and educational significance, these reefs face increasing threats from urbanization, infrastructure development, and uncontrolled quarrying for construction materials. Remote sensing and field observations over the past two decades document the progressive destruction of outcrops, eroding both their scientific value and geotourism potential. Early investigations provided only reconnaissance-level mapping, basic stratigraphy, and paleontological descriptions (Coulson \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e1936\u003c/span\u003e; Stauffer \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e1968\u003c/span\u003e; Barnett et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1966\u003c/span\u003e; Talent and Mawson \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e1979\u003c/span\u003e; Shah \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2009\u003c/span\u003e), leaving major gaps in the understanding of their petrology, diagenetic evolution, and engineering behaviour (Price and De Freitas \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Tugrul and Gurpinar \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e1997\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe described carbonate bodies represent the first Palaeozoic reefs discovered in Pakistan and contain a fossil fauna that is entirely new to Pakistan. Life changed so much during the Palaeozoic era that many of the organisms that lived during the later Palaeozoic were much closer to those of today. The available literature on the areas only manifests the stratigraphy of the siluro-devonian reef complexes, which lacks important of paleontological and diagenetic information and stratigraphic details of the Ghundai Sar formation are not well-documented and need further investigation.\u003c/p\u003e\u003cp\u003eThis study provides the first integrated geological, petrographic, and geotechnical assessment of the Nowshera Reef (NR) and Ghundai Sar Formation (GS). It characterizes the petrological and diagenetic features of the reefal carbonates and evaluates how these attributes influence their geotechnical behavior. The study further quantifies their mechanical properties through uniaxial compressive strength (UCS), uniaxial tensile strength (UTS), Los Angeles abrasion, and aggregate impact tests, and assesses their geotechnical suitability for construction applications, while recommending alternative aggregate sources to support geoheritage conservation. This integrated approach provides a foundation for balancing sustainable resource utilization with the preservation of Pakistan\u0026rsquo;s unique Siluro-Devonian reef complexes.\u003c/p\u003e"},{"header":"2 Geology of the Study Area","content":"\u003ch2\u003e2.1 Systematic literature review\u003c/h2\u003e\n\u003cp\u003eTeichert and Stauffer (1965) contributed to the faunal description of the Siluro-Devonian rocks of the Nowshera area and reported them to belong to the Silurian-Devonian period. Based on conodonts evidence, a similar age was determined for these rocks by Barnett et al. (1966). However, the correlation and stratigraphy of different carbonates and clastic sediments created some uncertainty. The formation was later described in detail by Stauffer (1968) and by Ali and Anwar (1969), who interpreted these rocks as part of a Reefal complex.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe current work offers significant of the target Silurian-Devonian reef complexes, it is primary outcome is the classification of these reefal complexes on the basis of outcrop-scale structure, an integrated approach-incorporating, meso-, and micro-level investigation will help biogenic components and diagenetic feature of the study area. Furthermore petrographical and geotechnical investigation of these reefs will facilitate regional comparison of aggregate and dimension stone resources with other formations.\u003c/p\u003e\n\u003ch2\u003e2.2 Location and Basin Context\u003c/h2\u003e\n\u003cp\u003eThe study area is situated in the Peshawar Basin of Khyber Pakhtunkhwa, northwestern Pakistan, along the northern margin of Gondwana. The Peshawar Basin is 8300 kilometers an intramontane depression bounded by the Main Boundary Thrust to the south and the Main Mantle Thrust to the north, and it preserves a thick Paleozoic to Cenozoic sedimentary succession (Pogue 1986; Kazmi and Jan 1997). Within this basin, the Nowshera Reef and the Ghundai Sar Formation represent two well-preserved Siluro-Devonian reef complexes (Fig. 1). These outcrops are among the few remaining Paleozoic reefal successions in the region and provide valuable records of early reef-building processes and shallow-marine depositional environments (Yaseen et al. 2019).\u003c/p\u003e\n\u003cp\u003eBoth the Ghundai Sar Formation and Nowshera Reef are dominated by calcite, dolomite, and abundant fossil fragments, reflecting complex depositional and diagenetic histories. Fig. 1 and Fig. 2 summarizes the spatial distribution of these reef complexes relative to major lithological units and fault systems in the Peshawar Basin.\u003c/p\u003e\n\u003ch2\u003e2.3 Nowshera Reef\u003c/h2\u003e\n\u003cp\u003eThe Nowshera Reef occurs about 3.5 km north of Nowshera city (34\u0026deg;01\u0026apos;44\u0026quot;N, 71\u0026deg;59\u0026apos;54\u0026quot;E) and extends laterally for approximately 20 km across isolated hills. It comprises fossiliferous limestone, dolomitic to marbleized limestone, calcareous quartzite, and minor argillite (Table 1). Stauffer (1968) subdivided the reef into a central reef-core unit and marginal reef breccias composed of fossil debris. These deposits form the youngest Paleozoic strata in this part of the basin and are unconformably overlain by the Jafar Kandao Formation near Swabi. Age interpretations, based on conodont and macrofossil assemblages, indicate an Early Devonian (Lochkovian) age (Talent and Mawson 1979; Shah 2009). Table 1 presents representative field photographs and (Fig. 2) lithological details of the Nowshera Formation.\u003c/p\u003e\n\u003ch2\u003e2.4 Ghundai Sar Formation\u003c/h2\u003e\n\u003cp\u003eThe Ghundai Sar Formation is located north of Jamrud Fort along the Warsak Canal and is similarly assigned a Siluro-Devonian age. The reef complex strikes east west and dips northward, forming a prominent isolated hill complex. Khan (1969) subdivided the formation into four lithological units: (i) grey to yellowish-grey dolomitized quartzite, (ii) talus and reef breccia, (iii) crinoidal limestone interbedded with phyllites, and (iv) a reef-core unit. These units collectively record dynamic shallow-marine depositional and diagenetic conditions during reef development. Table 2 present field photographs and lithological details of the Ghundai Sar Formation.\u003c/p\u003e"},{"header":"3 Methodology","content":"\u003cp\u003eThis study adopted a comprehensive methodology that integrated detailed field investigations with laboratory-based petrographic and geotechnical analyses. Fieldwork was carried out across the Siluro-Devonian reef complexes to document their structural, stratigraphic, and facies characteristics and to collect fresh, undeformed samples for subsequent testing. A total of 52 representative rock samples were collected from larger outcrops of the Nowshera Reef and Ghundai Sar Formation in the Peshawar Basin. Of these, 44 hand specimens (approximately 0.5 kg each) were designated for thin-section petrography, while larger bulk blocks, measuring 2-2.5 feet in length and 0.5-1 foot in thickness, were extracted for coring and mechanical testing. All samples were systematically labelled and transported to the National Centre of Excellence in Geology (NCEG), University of Peshawar, for further analyses.\u003c/p\u003e\u003cp\u003eField observations were conducted at both macro- and meso-scales. At the macro-scale, emphasis was placed on mapping large-scale structural features of the reef bodies, documenting their lateral continuity, and establishing stratigraphic relationships with adjacent lithologies. At the meso-scale, internal architectural features were examined, focusing on the constituents of the reef complexes, their vertical and lateral facies relationships, and other intermediate-scale characteristics that could influence mechanical behaviour. These observations were used to guide the sampling strategy and provided the contextual framework for laboratory interpretations.\u003c/p\u003e\u003cp\u003eLaboratory investigations were divided into petrographic and geotechnical components, for Petrographic analysis preparation of thin sections from 52 samples for microscopic study, which were examined under a Nikon LV100ND Polarizing Microscope at NCEG to determine mineralogy, textural attributes, porosity types, and diagenetic features such as dolomitization, cementation, and recrystallization. For geotechnical testing, 14 cores were drilled from the bulk blocks using a Universal Coring drill Machine, including six cores (GS1-GS6) from the Ghundai Sar Formation and eight cores (NR1-NR8) from the Nowshera Reef (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Physical property tests, including water absorption, specific gravity, and porosity measurements, were performed on the cores sample, followed by mechanical strength tests such as uniaxial compressive strength (UCS) and uniaxial tensile strength (UTS). Additionally, Los Angeles Abrasion (LAA) and Aggregate Impact Value (AIV) tests were conducted to evaluate aggregate durability. All sample preparation and testing procedures strictly adhered to ASTM International standards (1971, 1986, 2006, 2009, 2016).\u003c/p\u003e\u003cp\u003eField observations, petrographic results, and geotechnical data were integrated to interpret the diagenetic history and engineering properties of the studied reef complexes. This combined dataset allowed for the establishment of robust correlations between depositional fabrics, diagenetic modifications, and the mechanical performance of the carbonate rocks. The results of these analyses, along with their implications for dimension stone and aggregate resource potential, are presented in the subsequent sections of this manuscript.\u003c/p\u003e"},{"header":"4 Results","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e4.1 Macroscopic Analysis\u003c/h2\u003e\u003cp\u003eThe Ghundai Sar Formation and Nowshera Reef exhibit pronounced diagenetic alterations, including dolomitization, neomorphism, cementation, micritization, dissolution, and compaction, which have modified the original depositional fabrics. Both formations are primarily composed of limestone, dolomite, and subordinate quartzite, and host a diverse suite of fossils such as corals, crinoids, stromatoporoids, graptolites, bryozoans, gastropods, and cephalopods (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Fossilized honeycomb corals (favositids) are particularly abundant in the Ghundai Sar Formation and indicate a middle Silurian to lower Devonian age, while the occurrence of graptolites with variable branching morphologies suggests deposition in relatively deeper fore-reef settings. Crinoids, represented by stem fragments and isolated ossicles, are common in both formations and reflect periodic reefal environmental conditions. Stromatoporoids, preserved in the Nowshera Reef, are laminated calcified sponges that served as major reef-building organisms during the Middle Ordovician to Late Devonian and are characterized by well-developed laminae, pillars, and galleries (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Other faunal elements include coiled gastropods and cephalopods, bryozoans forming delicate colonial frameworks, and mollusks with diverse shell morphologies (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). These fossil assemblages provide important paleoecological information on the zonation of ancient reef ecosystems, with stromatoporoids and corals dominating reef-core facies and crinoids and graptolites being more prevalent in deeper fore-reef environments.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e4.2 Microscopic Analysis\u003c/h2\u003e\u003cp\u003ePetrographic analysis shows that the reef complexes are dominated by coarse-grained calcite and dolomite (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Calcite occurs as anhedral to subhedral crystals with characteristic rhombohedral cleavage and pearly-gray interference colors under cross-polarized light, while dolomite appears as both primary grains and secondary replacement phases displaying perfect rhombohedral cleavage. Extensive micritization is evident, with algal-bored grains enclosed by micritic envelopes indicative of shallow marine phreatic conditions. Dissolution features are common in shoal and foreshore facies, generating secondary porosity through selective leaching of unstable grains. Cementation occurs in multiple forms, including syntaxial overgrowths on echinoderm fragments, granular and drusy mosaic cements, and late-stage blocky calcite cements that occlude remaining pore spaces. Neomorphic recrystallization and dolomitization locally obscure primary textures, forming mosaics ranging from microcrystalline to coarsely crystalline dolomite. Microfacies analysis demonstrates clear relationships between depositional environment, fossil assemblages, and diagenetic overprint. Reef-core facies display the highest biological framework development and marine cementation, whereas back-reef and lagoonal deposits exhibit stronger evidence of meteoric diagenesis. These petrographic characteristics, combined with the fossil assemblages, indicate the complex interplay of biological, sedimentological, and diagenetic processes that shaped the present-day fabrics of the studied carbonate rocks.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e4.3 Geotechnical Properties\u003c/h2\u003e\u003cp\u003eGeotechnical testing reveals distinct contrasts between the Ghundai Sar Formation (GS) and the Nowshera Reef (NR) in porosity, strength, and durability (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Water absorption and porosity are consistently low in GS (0.08\u0026ndash;0.14% and 0.21\u0026ndash;0.38%), reflecting its dense, uniform fabric, whereas NR exhibits slightly higher and more variable values (0.10\u0026ndash;0.33% and 0.29\u0026ndash;0.93%). Both formations have specific gravity values above 2.73, with NR reaching 2.86, confirming their suitability for structural and dimension stone use.\u003c/p\u003e\u003cp\u003eUniaxial compressive strength (UCS) according with (ASTM: D2938\u0026ndash;95) ranges from 19.8\u0026ndash;35.9 MPa in GS and 19.1\u0026ndash;58.2 MPa in NR, with the highest values in NR5 and NR6. Uniaxial tensile strength (UTS) (ASTM: D3967\u0026ndash;16) shows a similar trend: GS ranges 3.84\u0026ndash;13.26 MPa, while NR reaches 5.51\u0026ndash;13.85 MPa. These results indicate that NR locally attains higher strength due to better cementation and partial dolomitization.\u003c/p\u003e\u003cp\u003eDurability indices confirm moderate wear resistance. Los Angeles abrasion (LAA) and Aggregate Impact Values (AIV) are 27-27.2% and 24.3-24.76% for GS, versus 23.1\u0026ndash;23.3% and 21.02\u0026ndash;22.4% for NR, indicating that NR is slightly more resistant to mechanical wear. These findings suggest both formations are technically suitable for construction applications, with NR providing occasional high-strength blocks appropriate for dimension stone. Property distributions and formation variability are illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eA-I.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eSummary of geotechnical properties of the Ghundai Sar Formation and Nowshera Reef.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"9\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFormation\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSample\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eUCS(Mpa)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eUTS(Mpa)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eLAA(%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" 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colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e2.736\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.21\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eGS6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e35.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.84\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e2.787\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.38\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAverage\u003c/p\u003e\u003cp\u003eMin-Max\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e27.62\u003c/p\u003e\u003cp\u003e19.8\u0026ndash;35.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e8.06\u003c/p\u003e\u003cp\u003e3.84\u0026ndash;13.26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e27-27.2%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e24.3-24.76%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.105\u003c/p\u003e\u003cp\u003e0.08\u0026ndash;0.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e2.742\u003c/p\u003e\u003cp\u003e2.730\u0026ndash;2.787\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.28\u003c/p\u003e\u003cp\u003e0.21\u0026ndash;0.38\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNR1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e32.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e12.86\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e2.847\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.49\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNR2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e19.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e13.85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e2.848\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.50\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNR3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e32.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10.22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e2.834\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.93\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNowshera Reef\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNR4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e34.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e8.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e2.847\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.88\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNR5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e58.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e8.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e2.809\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.51\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNR6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e49.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e2.856\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.56\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNR7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e36.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e9.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e2.788\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.29\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNR8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e25.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10.54\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e2.858\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.48\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAverage\u003c/p\u003e\u003cp\u003eMin-Max\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e35.86\u003c/p\u003e\u003cp\u003e19.1\u0026ndash;58.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e9.86\u003c/p\u003e\u003cp\u003e5.51\u0026ndash;13.85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e23.1\u0026ndash;23.3%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e21.02\u0026ndash;22.4%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.205\u003c/p\u003e\u003cp\u003e0.10\u0026ndash;0.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e2.835\u003c/p\u003e\u003cp\u003e2.788\u0026ndash;2.858\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.58\u003c/p\u003e\u003cp\u003e0.29\u0026ndash;0.93\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eWA\u0026thinsp;=\u0026thinsp;water absorption; Gs\u0026thinsp;=\u0026thinsp;specific gravity; n\u0026thinsp;=\u0026thinsp;porosity; UCS\u0026thinsp;=\u0026thinsp;uniaxial compressive strength; UTS\u0026thinsp;=\u0026thinsp;uniaxial tensile strength; LAA\u0026thinsp;=\u0026thinsp;Los Angeles abrasion; AIV\u0026thinsp;=\u0026thinsp;aggregate impact value.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"5 Discussion","content":"\u003cp\u003ePetrographic and physico-mechanical analysis indicates that the Ghundai Sar Formation (GS) and Nowshera Reef (NR) are medium- to coarse-grained carbonate rocks composed primarily of calcite and dolomite. Under plane-polarized light, calcite appears mostly anhedral to subhedral with cloudy to clear textures, low to moderate relief, and rhombohedral cleavage. Dolomite occurs as high-relief, fine- to coarse-grained colorless crystals with perfect rhombohedral cleavage. Both formations exhibit pervasive diagenetic overprinting, including micritization, dissolution, cementation, neomorphism, and localized dolomitization-features that influence porosity and mechanical performance. Void-filling cements manifest as syntaxial overgrowths, granular mosaics, and coarse blocky calcite, often enhancing fabric strength through pore occlusion.\u003c/p\u003e\u003cp\u003eFossil assemblages include honeycomb corals (favositids), crinoids, stromatoporoids, graptolites, bryozoans, gastropods, and cephalopods, with their distribution reflecting reef zonation. Stromatoporoids and corals dominate reef core facies, while crinoids and graptolites are more common in fore-reef and back-reef environments. These faunal assemblages confirm the Siluro-Devonian age and add substantial scientific value, warranting geoheritage designation.\u003c/p\u003e\u003cp\u003eThe depositional environment of the Nowshera Reef and Ghundai Sar Formation are interpreated as a shallow marine reefal system and an outer-shelf to basinal system, respectively (Stauffer, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e1968\u003c/span\u003e; Khan et al.,1989), interpretive diagram of depositional environments is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, (this study; modified after Wilson, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e1975\u003c/span\u003e; James and Kendall, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e1992\u003c/span\u003e). The fossils of Nowshera reef, stromatolites highlight both biological activity and open marine connection, the depositional setting reflect a shallow, tropical carbonates reef system influenced by both biological construction and early diagenesis. The Ghundai Sar formation therefore represent a carbonates outer shelf slope basinal system, where the presence of graptolite confirms depostion in open marine condition with connection to deeper basins.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe formations are classified as moderately strong (ISRM 1981), with NR exhibiting higher UCS (mean: 35.9 MPa; peak: 58.2 MPa) and UTS (9.9 MPa) than GS (UCS: 27.6 MPa; UTS: 8.1 MPa). Durability indices such as Los Angeles abrasion (NR: 23.3%; GS: 27.2%) and impact value (NR: 21.0; GS: 24.8%) show that both satisfy general construction specifications, though NR offers better performance. Specific gravity values of 2.835 g/cm\u0026sup3; for NR and 2.742 g/cm\u0026sup3; for GS further reflect denser fabrics in NR. However, field observations during sample preparation revealed flaky and elongated fragments in both formations, suggesting potential issues with particle shape that could affect performance as high-grade aggregate.\u003c/p\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e5.1 Relationships Between Petrography and Physico-Mechanical Properties\u003c/h2\u003e\u003cp\u003eMechanical behavior correlates closely with petrographic attributes. Denser fabrics-marked by micritic envelopes, tight cementation, and dolomitized zones-tend to yield higher UCS and UTS values. Scatter plots (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eA-C) illustrate negative correlations between UCS and both porosity and water absorption, while a positive correlation exists between UCS and UTS. Bar charts and boxplots (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eD-I) confirm that NR has a broader range in UCS and porosity than GS, reflecting lithofacies heterogeneity.\u003c/p\u003e\u003cp\u003eStatistical testing shows that UCS in NR is about 30% higher than in GS. A two-sample t-test (t\u0026thinsp;=\u0026thinsp;1.65, p\u0026thinsp;=\u0026thinsp;0.1293) indicates that this difference is not statistically significant at the 95% confidence level. Similarly, UTS values are higher in NR (9.87 MPa vs. 8.06 MPa; t\u0026thinsp;=\u0026thinsp;1.11, p\u0026thinsp;=\u0026thinsp;0.2818) but again not significant. In contrast, porosity differences are statistically significant (NR mean: 0.58%; GS: 0.28%; t\u0026thinsp;=\u0026thinsp;3.47, p\u0026thinsp;=\u0026thinsp;0.0052), attributed to fossil dissolution and secondary porosity in NR\u0026rsquo;s heterogeneous facies. Dense boundstone fabrics in reef-core samples (e.g., NR5) yield UCS values above 50 MPa, while GS consists largely of uniform micritic to packstone textures with moderate sparry cementation and minimal dolomitization, yielding UCS\u0026thinsp;~\u0026thinsp;25\u0026ndash;35 MPa.\u003c/p\u003e\u003cp\u003eThese trends are consistent with carbonate literature, where diagenetic evolution, cementation, and fabric control strength and durability (Choquette and Pray 1970; Shakoor and Bonelli \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e1991\u003c/span\u003e; Bell \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Lucia 2007; Baechle et al. 2008). Even where direct linear correlations are weak, facies-based differences emphasize the predictive value of microstructural interpretation in geomechanical behaviour and resource evaluation.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e5.2 Geotechnical Suitability and Conservation\u003c/h2\u003e\u003cp\u003eBoth GS and NR are mechanically serviceable as construction aggregates, yet they are not optimal when compared to other regional carbonate formations. Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows that the Kohat (KF) and Shekhan (SF) formations outperform NR and GS with higher UCS (\u0026gt;\u0026thinsp;39 MPa), lower abrasion and impact values (\u0026asymp;\u0026thinsp;20% and 11\u0026ndash;16%, respectively), and comparable porosity and absorption. While NR and GS meet general specifications, their mechanical variability and visual degradation (flaky fragments) raise concerns for high-performance use.\u003c/p\u003e\u003cp\u003eFrom a conservation perspective, NR and GS are exceptional fossiliferous reef complexes with complete reef-core, fore-reef, and back-reef facies preserved. Field observations and Landsat imagery (2005\u0026ndash;2022) reveal ongoing excavation and reef depletion (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e), posing imminent risk to this rare geological archive. As global awareness of fossil reef preservation grows, it is recommended that mining be redirected toward mechanically superior but geologically less significant formations such as KF and SF. This dual strategy supports both sustainable development and preservation of Pakistan\u0026rsquo;s mid-Paleozoic geological heritage\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eComparison of Geotechnical properties of ccurrent study with previous studies\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"16\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c14\" colnum=\"14\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c15\" colnum=\"15\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c16\" colnum=\"16\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGeotechnical Properties\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003eThis Study\u003c/p\u003e\u003cp\u003e(GS) (NR)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c6\" namest=\"c4\"\u003e\u003cp\u003eAsif et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2022\u003c/span\u003e\u003c/p\u003e\u003cp\u003e(WL) (SF) (KF)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e\u003cp\u003eSarfaraz et al. 2021\u003c/p\u003e\u003cp\u003e(MF) (ML)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c11\" namest=\"c9\"\u003e\u003cp\u003eUllah et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2020\u003c/span\u003e\u003c/p\u003e\u003cp\u003e(LL) (SH) (SSF)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c13\" namest=\"c12\"\u003e\u003cp\u003eRehman et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2020\u003c/span\u003e\u003c/p\u003e\u003cp\u003e(SSF) (KW)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c14\"\u003e\u003cp\u003eAnjum et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2018\u003c/span\u003e (KL)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c16\" namest=\"c15\"\u003e\u003cp\u003eNaeem et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2014\u003c/span\u003e\u003c/p\u003e\u003cp\u003e(ML) (KW)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLAA(%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e27.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e23.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e23.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e22.90\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e19.99\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e25.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e16.93\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e23.88\u0026ndash;24.38\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e14.08\u0026ndash;16.53\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e14.81\u0026ndash;16.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e27.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e20.86\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u003cp\u003e26.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u003cp\u003e23.93\u0026ndash;25.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u003cp\u003e14.93\u0026ndash;15.85\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAIV(%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e24.76\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e21.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e16.80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e14.80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e14.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e20.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e22.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e13.70\u0026ndash;15.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e11.80\u0026ndash;14.90\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e11.38\u0026ndash;12.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e14.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e14.89\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u003cp\u003e_ -\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u003cp\u003e15.36\u0026ndash;16.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u003cp\u003e11.40\u0026ndash;12.71\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eUCS(MPa)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e27.62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e35.86\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e93.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e69.31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u003cp\u003e19.86\u0026ndash;39.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eUTS (MPa)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8.06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e9.86\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e-\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eWA(%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.105\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.205\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.72\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.64\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.68\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.98\u0026ndash;1.36\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.25\u0026ndash;0.58\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e0.38\u0026ndash;1.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e0.81\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e0.89\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u003cp\u003e0.68\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u003cp\u003e0.94\u0026ndash;1.61\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u003cp\u003e0.60\u0026ndash;0.69\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSG (g/cm\u0026sup3;)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2.74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.83\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e2.71\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e2.76\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e2.63\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e2.70\u0026ndash;2.78\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e2.60\u0026ndash;2.64\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e2.61\u0026ndash;2.66\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e2.68\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e2.73\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u003cp\u003e2.72\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u003cp\u003e2.60\u0026ndash;2.63\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u003cp\u003e2.72\u0026ndash;2.77\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003en (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.28\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.58\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e2.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e2.33\u0026ndash;2.69\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e1.14\u0026ndash;1.44\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e1.04\u0026ndash;1.61\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u003cp\u003e2.31\u0026ndash;2.98\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u003cp\u003e1.76\u0026ndash;2.12\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"16\" nameend=\"c16\" namest=\"c1\"\u003e\u003cp\u003eGS\u0026thinsp;=\u0026thinsp;Ghundai Sar Formation; NR\u0026thinsp;=\u0026thinsp;Nowshera Reef; WL\u0026thinsp;=\u0026thinsp;Wargal limestone; SF\u0026thinsp;=\u0026thinsp;Shekhan Formation; KF\u0026thinsp;=\u0026thinsp;Kohat Formation; MF\u0026thinsp;=\u0026thinsp;Muzaffarabad formation; ML\u0026thinsp;=\u0026thinsp;Margalla Hill limestone; LL\u0026thinsp;=\u0026thinsp;Lockhart limestone; SH\u0026thinsp;=\u0026thinsp;Shekhai Formation; SSF\u0026thinsp;=\u0026thinsp;Samana Suk Formation; KW\u0026thinsp;=\u0026thinsp;Kawagarh Formation; KL\u0026thinsp;=\u0026thinsp;Khyber limestone.\u003c/p\u003e\u003cp\u003eGeotechnical properties: LAA\u0026thinsp;=\u0026thinsp;Los Angeles abrasion; AIV\u0026thinsp;=\u0026thinsp;Aggregate impact value; UCS\u0026thinsp;=\u0026thinsp;Uniaxial compressive strength; UTS\u0026thinsp;=\u0026thinsp;Uniaxial (Brazilian) tensile strength; WA\u0026thinsp;=\u0026thinsp;Water absorption; SG\u0026thinsp;=\u0026thinsp;Specific gravity; n\u0026thinsp;=\u0026thinsp;Aggregate porosity.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e5.3 Global Context: Comparison with Silurian-Devonian Reef Complexes\u003c/h2\u003e\u003cp\u003eThe Paleozoic reef complexes in Pakistan host a rich and diverse fossil fauna, with ages constrained to the Silurian-Early Middle Devonian based on biostratigraphic evidence (Shah \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Talent and Mawson \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e1979\u003c/span\u003e). Their faunal composition suggests possible correlation with coeval Paleozoic limestones in Afghanistan, indicating broader regional continuity in reef development along the northern Gondwanan margin.\u003c/p\u003e\u003cp\u003eThe geological and mechanical characteristics of NR and GS align with mid-Paleozoic reef systems globally. In the Canning Basin (Western Australia), reef-core limestones exhibit early cementation and porosity occlusion similar to NR, while dolomitized back-reef zones show increased heterogeneity in porosity and strength. Banks Island reefs (Arctic Canada) also consist of low-porosity, tightly cemented limestones, with weaker zones linked to fossil abundance and fracturing.\u003c/p\u003e\u003cp\u003eIn the U.S. Midwest, Silurian reef complexes such as Thornton Reef were initially exploited as aggregate sources but later designated as geoheritage sites due to their paleontological significance (Mikulic and Kluessendorf 2023). These reefs showed mechanical heterogeneity, with dolomitized portions being more suitable for construction use. Similarly, Saaremaa Island in Estonia has proposed legal protection for Silurian reef cliffs with unique fossil content (Vinn et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Lithuanian Silurian reef studies further emphasize the limitations of such diagenetically hardened limestones for reservoir or engineering purposes due to low matrix porosity (Kaminskaite-Baranauskiene et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThese global analogues demonstrate a consistent pattern: Silurian-Devonian reefs are mechanically heterogeneous, diagenetically altered, and of high scientific value. As such, international best practices increasingly promote geoheritage designation and restrict quarrying in such formations an approach also recommended here for the NR and GS reef systems.\u003c/p\u003e\u003c/div\u003e"},{"header":"6 Conclusions","content":"\u003cp\u003eThis study presents the first integrated petrographic and geotechnical characterization of the Siluro-Devonian reef complexes of the Peshawar Basin, focusing on the Nowshera Reef (NR) and Ghundai Sar Formation (GS). The study has several conclusions. First, these reefal limestones, dominated by calcite and dolomite with distinct facies architectures and diagenetic overprints (micritization, dolomitization, and cementation), preserve a rich Siluro-Devonian fossil assemblage including stromatoporoids, honeycomb corals, bryozoans, and crinoids. The Nowshera Reef is one of the few intact mid-Paleozoic reef systems on the northern Gondwanan margin. The study documents facies-specific variation in diagenetic textures and early cementation, offering rare paleoenvironmental insights from Pakistan.\u003c/p\u003e\u003cp\u003eSecond, mechanical characterization revealed that NR exhibits higher strength and porosity variability (UCS: 19–58 MPa, avg. 35.9 MPa; porosity up to 0.93%) than GS (UCS: 19.8–35.9 MPa, avg. 27.6 MPa; porosity up to 0.38%). The mean UCS of NR is ~ 30% higher than GS, a difference that is not statistically significant (p = 0.1293) but consistent with petrographic evidence of greater cementation and dolomite content. These results align with international data on Silurian-Devonian reefs, which often show moderate strength and fabric-controlled heterogeneity (e.g., Canning Basin, Banks Island, Illinois Thornton Reef). The flaky particle shape and moderate abrasion resistance (LAA ~ 23–27%) limit their utility for high-performance construction applications.\u003c/p\u003e\u003cp\u003eThird, while the geotechnical properties of NR and GS meet general construction standards, they are not exceptional. Comparisons with younger Pakistani formations (e.g., Kohat and Shekhan formations with UCS \u0026gt; 39 MPa) indicate that stronger, more durable aggregate alternatives exist. This supports the argument that quarrying these globally significant reefs for average-quality aggregate is scientifically unsound.\u003c/p\u003e\u003cp\u003eFourth, landsat imagery (2005–2022) and field observations reveal accelerating degradation of reef outcrops from unregulated extraction. Given their fossil richness, paleoenvironmental importance, and rarity, NR and GS merit formal geoheritage designation. Their conservation would align Pakistan with global best practices (e.g., protection of Silurian reefs in Estonia and USA) and fill a national void in formally recognized geoheritage sites.\u003c/p\u003e\u003cp\u003eFifth, this study offers a replicable model for evaluating geologically significant sites facing extraction pressures. By combining petrographic, mechanical, and sustainability analyses, it demonstrates how to inform conservation policy with empirical data. The dataset is also relevant to researchers studying carbonate reservoir analogues or Paleozoic reef evolution globally.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"7 Recommendations","content":"\u003col style=\"list-style-type: lower-roman;\"\u003e\n \u003cli\u003eNR and GS should be nominated for national geoheritage status to ensure long-term preservation, supported by educational and legislative outreach.\u003c/li\u003e\n \u003cli\u003ePrioritize the use of Kohat, Shekhan, and Margalla Hill formations as construction aggregates, given their superior mechanical properties and lower heritage value.\u003c/li\u003e\n \u003cli\u003eImplement zoning regulations and incentives to steer construction projects away from geoheritage site\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003ch2\u003eCompeting Interests\u003c/h2\u003e\u003cp\u003eThe authors declare no competing financial or non-financial interests related to this work.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAll authors have equally contributions.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe authors gratefully acknowledge the National Centre of Excellence in Geology (NCEG), University of Peshawar, for providing funding and laboratory facilities.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAnjum MN, Ali N, Rehman ZU, Ghayas M, Ahmad W (2018) Rock aggregate potential of the limestone units in the Khyber Formation, Khyber ranges, Pakistan. 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US Bur Mines Rep Invest 6702\u003c/li\u003e\n \u003cli\u003eISRM (International Society for Rock Mechanics) (1981) Rock characterization, testing and monitoring. In: Brown ET (ed) ISRM suggested methods. Pergamon, Oxford\u003c/li\u003e\n \u003cli\u003eJames, NP, Kendall AC (1992) Introduction to carbonate and evaporite facies models. In Walker RG, James (Eds) Facies models: Response to sea level change. Geological Association o Canada\u003c/li\u003e\n \u003cli\u003eKaminskaite-Baranauskiene I, Cichon-Pupienis A, Makauskas P (2024) Silurian barrier reef in Lithuania: Reservoir properties and low enthalpy geothermal heat potential. Heliyon 10(4)\\:e26360. [https://doi.org/10.1016/j.heliyon.2024.e26360]\u003c/li\u003e\n \u003cli\u003eKazmi AH, Jan MQ (1997) Geology \u0026nbsp;and \u0026nbsp;tectonics \u0026nbsp; of \u0026nbsp;Pakistan. Graphic Publishers, Karachi, 554 p\u003c/li\u003e\n \u003cli\u003eKhan MA (1969) Siluro-Devonian Reef Complex of Ghundai Sar and vicinity, Jamrud, Khyber Agency. Geol Bull Univ Peshawar 4:33\u0026ndash;43\u003c/li\u003e\n \u003cli\u003eKhan SR, Kakar DM, Jan MR, Din M, Ahmed I (1989) Stratigraphy and structure of the Peshawar basin, Pakistan. Geol Bull Univ Peshawar, 22(1), 1-15\u003c/li\u003e\n \u003cli\u003eMawson R, Talent JA, Molloy P, Simpson AJ (2003) Siluro-Devonian (Pridoli\u0026ndash;Lochkovian and early Emsian) conodonts from the Nowshera area, Pakistan: implications for the mid-Palaeozoic stratigraphy of the Peshawar Basin. Courier Forsch Senckenberg 245:83\u0026ndash;105\u003c/li\u003e\n \u003cli\u003eMikulic DG, Kluessendorf J (2024) Geoheritage and geoconservation in the American Midwest: Silurian reefs of the Milwaukee\u0026ndash;Chicago region. In: Clary RM, Pyle EJ, Andrews WM (eds) Geology\u0026rsquo;s significant sites and their contributions to geoheritage. Geological Society, London, Special Publications, 543:135\u0026ndash;148. [https://doi.org/10.1144/SP543-2023-51]\u003c/li\u003e\n \u003cli\u003eNaeem M, Khalid P, Sanaullah M, Din ZU (2014) Physio-mechanical and aggregate properties of limestones from Pakistan. Acta Geod Geophys 49:369\u0026ndash;380. [https://doi.org/10.1007/s40328-014-0054-8]\u003c/li\u003e\n \u003cli\u003ePogue KR, Hussain A (1986) New light on stratigraphy of Nowshera area and the discovery of early to middle Ordovician trace fossils in NWFP Pakistan. Geol Surv Pak Inf Release 135:15\u003c/li\u003e\n \u003cli\u003ePrice DG, De Freitas MH (1995) Engineering geology: principles and practices. Springer-Verlag, Berlin Heidelberg\u003c/li\u003e\n \u003cli\u003eRehman G, Zhang G, Rahman MU, Rahman NU, Usman T, Imraz M (2020) The engineering assessments and potential aggregate analysis of Mesozoic carbonates of Kohat Hills range, KP, Pakistan. Acta Geod Geophys 55:477\u0026ndash;493. [https://doi.org/10.1007/s40328-020-00301-9]\u003c/li\u003e\n \u003cli\u003eSarfraz Y, Basharat M, Riaz MT, Khan MA, Shahzad A, Ahmed KS (2021) Evaluation of physicomechanical properties of crushed rock aggregates: a case study from the Sub-Himalaya, Pakistan. Acta Montan Slovaca 26(3):375\u0026ndash;384. [https://doi.org/10.46544/AMS.v26i3.07]\u003c/li\u003e\n \u003cli\u003eShah SMI (2009) Stratigraphy \u0026nbsp;of \u0026nbsp;Pakistan. \u0026nbsp; Mem \u0026nbsp;Geol \u0026nbsp;Surv Pak \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; 12:138\u003c/li\u003e\n \u003cli\u003eShakoor A, Bonelli RE (1991) Relationship between petrographic characteristics, engineering index properties, and mechanical properties of selected sandstones. Bull Int Assoc Eng Geol 1:55\u0026ndash;71. [https://doi.org/10.1007/BF02590228]\u003c/li\u003e\n \u003cli\u003eStauffer KW (1968) Siluro-Devonian Reef complex near Nowshera, West Pakistan. Geol Soc Am Bull 79:1131\u0026ndash;1350. [https://doi.org/10.1130/0016-7606(1968)79\\[1131\\:SRcNW\\]2.0.CO;2]\u003c/li\u003e\n \u003cli\u003eTalent JA, Mawson R (1979) Paleozoic\u0026ndash;Mesozoic biostratigraphy of Pakistan in relation to biogeography and the coalescence of Asia. In: Farah A, DeJong KA (eds) Geodynamics of Pakistan. Geological Survey of Pakistan, Quetta, pp 81\u0026ndash;102\u003c/li\u003e\n \u003cli\u003eTeichert C, Stauffer KW (1965) Paleozoic \u0026nbsp;reef \u0026nbsp;discovery \u0026nbsp; in \u0026nbsp;Pakistan. \u0026nbsp; \u0026nbsp; Geol \u0026nbsp; Surv Pak 14:3\u003c/li\u003e\n \u003cli\u003eTugrul A, Gurpinar O (1997) The effect of chemical weathering on the engineering properties of Eocene basalts in north-eastern Turkey. Environ Eng Geosci 3:225\u0026ndash;234. [https://doi.org/10.2113/gseegeosci.3.2.225]\u003c/li\u003e\n \u003cli\u003eUllah R, Ullah S, Rehman N, Ali F, Asim M, Tahir M, Ullah S, Muhammad S (2020) Aggregate suitability of the Late Permian Wargal Limestone at Kafar Kot Chashma Area, Khisor Range, Pakistan. Int J Econ Environ Geol 11(1):89\u0026ndash;94. [https://doi.org/10.46660/ijeeg.Vol11.Iss1.2020.418]\u003c/li\u003e\n \u003cli\u003eVinn O, Wilson MA, Isakar M, Toom U (2024) Two high value geoheritage sites on S\u0026otilde;rve Peninsula (Saaremaa Island, Estonia): a window to the unique Late Silurian fauna. Geoheritage 16(2):53\u0026ndash;68. [https://doi.org/10.1007/s12371-024-00957-7]\u003c/li\u003e\n \u003cli\u003eWilson JL (1975) Carbonate \u0026nbsp; \u0026nbsp;facies \u0026nbsp; \u0026nbsp;in \u0026nbsp; \u0026nbsp; geologic \u0026nbsp; \u0026nbsp;history. \u0026nbsp; Springer-Verlag, \u0026nbsp; \u0026nbsp;Berlin\u003c/li\u003e\n \u003cli\u003eYaseen M, Mukhtiar G, Muhammad NA, Sajid M, Irfan Ullah J, Mubbashir M, Emad Ullah, Waqas M (2019) A Novel Approach to Evaluate, Highlight, and Conserve the Geologically Significant Geoheritage Sites from the Peshawar Basin, Khyber Pakhtunkhwa, Pakistan: Insights into Their Geoscientific, Educational, and Social Importance. Geoheritage 4:1461-1474.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTable 1 and 2 are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"carbonates-and-evaporites","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"caev","sideBox":"Learn more about [Carbonates and Evaporites](http://link.springer.com/journal/13146)","snPcode":"13146","submissionUrl":"https://submission.nature.com/new-submission/13146/3","title":"Carbonates and Evaporites","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Peshawar Basin, Silurian-Devonian, Nowshera Formation, Ghundai Sar Formation, Engineering Properties, Geoheritage","lastPublishedDoi":"10.21203/rs.3.rs-7496598/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7496598/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe Nowshera Reef and Ghundai Sar Formation of the Peshawar Basin, Pakistan, represent rare Siluro-Devonian reef complexes that preserve key transitions in Paleozoic carbonate platform evolution. This study provides the first integrated assessment of their petrography, diagenesis, and engineering properties to inform both geoheritage conservation and resource management. Field observations reveal fore-reef, reef-core, and back-reef facies hosting diverse fossils-honeycomb corals, stromatoporoids, crinoids, and graptolites-within limestones and dolostones affected by dolomitization, micritization, and cementation. Microscopic analysis confirms calcite-dominated fabrics with localized dolomitization, syntaxial overgrowths, and neomorphic textures. Mechanical testing shows moderately strong rock properties, with uniaxial compressive strength ranging from 19 to 58 MPa and tensile strength from 4 to 14 MPa. Nowshera Reef exhibits slightly higher strength and lower abrasion than the Ghundai Sar Formation, attributed to denser cementation and lower porosity. However, both formations exhibit strength and durability metrics comparable to other Silurian reefs globally, such as those in Estonia, where quarrying pressures have prompted preservation efforts. Despite moderate suitability as aggregate sources, the scientific value of these fossil-rich carbonates outweighs their economic use. Given ongoing degradation due to unregulated extraction, the study recommends prioritizing alternative lithologies for construction and formally designating these reef complexes as protected geoheritage sites.\u003c/p\u003e","manuscriptTitle":"Petrological and Geotechnical Assessment of Siluro-Devonian Reef Complexes in the Peshawar Basin, Pakistan: Implications for Sustainable Resource and Geoheritage Management","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-17 13:34:27","doi":"10.21203/rs.3.rs-7496598/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-11-19T14:29:16+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-13T21:56:45+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-12T09:33:38+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-10T07:52:15+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"224284625174266480037107492137006303910","date":"2025-10-31T02:08:31+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"223423095826872432554529078926595786807","date":"2025-10-30T16:11:21+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"67100780578737790593560548632746303750","date":"2025-10-29T12:01:09+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-22T22:03:23+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"129565852127005261965988950395549162212","date":"2025-09-21T16:11:02+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-09-10T01:32:49+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-09-10T01:26:49+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-09-01T15:29:14+00:00","index":"","fulltext":""},{"type":"submitted","content":"Carbonates and Evaporites","date":"2025-08-30T16:50:52+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"carbonates-and-evaporites","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"caev","sideBox":"Learn more about [Carbonates and Evaporites](http://link.springer.com/journal/13146)","snPcode":"13146","submissionUrl":"https://submission.nature.com/new-submission/13146/3","title":"Carbonates and Evaporites","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"008fff85-159c-4c85-9c6a-39c35e2df7e0","owner":[],"postedDate":"September 17th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-04-07T16:09:40+00:00","versionOfRecord":{"articleIdentity":"rs-7496598","link":"https://doi.org/10.1007/s13146-026-01262-w","journal":{"identity":"carbonates-and-evaporites","isVorOnly":false,"title":"Carbonates and Evaporites"},"publishedOn":"2026-04-02 15:58:14","publishedOnDateReadable":"April 2nd, 2026"},"versionCreatedAt":"2025-09-17 13:34:27","video":"","vorDoi":"10.1007/s13146-026-01262-w","vorDoiUrl":"https://doi.org/10.1007/s13146-026-01262-w","workflowStages":[]},"version":"v1","identity":"rs-7496598","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7496598","identity":"rs-7496598","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}