Rock Typing, Diagenesis and Paleoenvironment of Middle Jurassic Tethys Ramp Carbonates, Sub-Himalayas, Pakistan

The Samana Suk Formation is extensively exposed across the Sub-Himalayan region of Pakistan, notably within the Salt Range and the Trans-Indus Ranges, where Jurassic carbonates dominate the stratigraphy. Although localized studies have been conducted, a comprehensive understanding of the link between exposures in these two regions has remained elusive. This study identifies five primary lithologies: limestone (78%), marl/shale (10%), dolomite (9.5%), irregular quartz-bearing limestone (1.5%), and sandstone (1%). Limestones in the Salt Range exhibit a range of textures, including fine- to coarse-grained, nodular, skeletal, micritic, oolitic, and intraclastic varieties. Seven distinct microfacies have been classified: mudstone, dolo-mudstone, bioclastic peloidal wackestone, bioclastic intraclastic grainstone, sandy echinoderm packstone, ooidal peloidal bioclastic grainstone, and peloidal grainstone. Stratigraphic sections in the Trans-Indus Ranges reveal considerable variability in thickness, facies composition, dolomitization intensity, quartz content, and diagenetic features. X-ray diffraction and scanning electron microscopy analyses confirm a predominantly carbonate mineralogy with well-developed microporosity. Above this Jurassic carbonate platform, the upper Paleocene Hangu Formation records a shift to subaerial depositional conditions. These findings collectively highlight the Samana Suk Formation as a valuable archive of Middle Jurassic paleoenvironments and suggest its potential as a hydrocarbon reservoir and a source of raw materials for the cement and construction industries.