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

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.