<p>The Margala Hill Limestone (northern Pakistan) offers key insights into karst collapse processes in foreland basin carbonates. This study integrates stratigraphic logging, petrographic analysis, geochemical proxies, stable isotopes, and mechanical testing to evaluate the mechanisms and controlling factors of collapse features. Facies analysis reveals a shallow-marine depositional setting, ranging from micrite-rich wackestones to sparite-cemented grainstones, later overprinted by diagenesis and karstification. Field and petrographic observations document dissolution-enlarged fractures, brecciation, stylolites, and cavity fills, with MHLC 7 (from the MHLC 1–7 facies succession) representing the most intensely altered interval. The limestone is dominated by calcite (&gt; 80%) with variable bioclast content (10–25%), while effective porosity is predominantly secondary, generated through dissolution and collapse brecciation. Geochemical and isotopic results indicate meteoric diagenesis as the main driver, marked by depleted δ¹⁸O values (–8‰ VPDB), reduced Sr, and elevated Mn and Fe in altered zones. Mechanical testing shows significant weakening in collapse horizons, where unconfined compressive strength declines to ~ 10&#xa0;MPa, compared to &gt; 30&#xa0;MPa in micritic, unaltered layers. Collectively, the results demonstrate that subaerial exposure, meteoric dissolution, and diagenetic modification governed collapse breccia development, producing mechanically unstable intervals. These findings provide a framework for identifying collapse-prone horizons and highlight implications for slope stability and geohazard assessment in the Islamabad–Rawalpindi region.</p>