Middle Eocene Carbonate Deposition and Sea-level Dynamics: Insights from the Zindapir Area, Eastern Sulaiman Range, Pakistan

The Middle Eocene rock units (Pir Koh Limestone and Drazinda Formation) are well exposed in the Zindapir region of Eastern Sulaiman Range, Pakistan. Pir Koh Limestone is 15–20 m thick and mostly consists of marls and limestone, however, 240 m-thick Drazinda Formation is primarily comprised of limestone and rare sandstone. The relatively quick sedimentation along the shelf with pulsated anoxia preserved abundance of organic matter. Foraminiferal species, both tiny and large, were found during paleontological analyses. Microfacies investigations reveal that the rich assemblage of larger benthic foraminifera with small bioclasts makes up Pir Koh Limestone which suggests deposition across the middle ramp to upper slope settings in well-circulated, open marine environments. However, the carbonate rich Drazinda Formation provide evidence of sporadic catastrophic sea level rise and fall under shallow marine depositional conditions. A second order in sea level that led to shallower to deeper open marine shelves (TST to HST) deposited Pir Koh Limestone. Multiple sea-level fluctuations resulted in the deposition of the Drazinda Formation, which is semi-restricted shallow shelf to open marine shelf settings (TST and HST). Pir Koh Limestone shallow shelf facies offer vuggy porosity and high reservoir potential. The Middle Eocene rocks in the study area offer critical insights into past marine environments and contribute to global understanding of Eocene climate dynamics and sea-level fluctuations.