ABSTRACT This study presents an integrated organic geochemical, petrological characteristics, biomarker, and elemental compositions of shale facies of Paleocene–Eocene Patala Formation. The dataset consists of an outcrop section and an exploratory well (Manzalai‐1) situated in the Kohat Plateau, Upper Indus Basin (North Pakistan). This work aimed to understand organic matter (OM) input and paleoenvironmental settings during the Late Paleocene time and their effect on organic carbon‐rich amassing in Patala shale facies. Geochemical analysis shows that most of the Patala shale sediments are characterized by >1–3.25 wt.% total organic carbon (TOC), demonstrating good OM accumulation under low‐oxygenated environmental settings. During deposition of Patala shale facies, the low‐oxygenated environmental settings (mainly anoxic to euxinic) of water column facilitated preservation of OM. It is revealed by comparatively low pristane (Pr)/phytane (Ph) ratio between 0.79 and 2.38 and relatively higher concentration of vanadium (V) compared to nickel (Ni), with high V/Ni ratio reaching 11 and V/(V + Ni) values as high as 0.92. The current study also investigated the source and origin of OM contribution into the Patala shale facies during deposition. The characteristics of hopane, tricyclic terpane, and sterane biomarkers provide evidence that the Patala shale facies contains mixed OM of planktonic bacteria with terrigenous plant inputs. The finding is confirmed by the presence of marine microorganisms such as coccolithophore plankton and fossilized bacteria, as indicated by scanning electron microscopy (SEM) results. Paleoclimatic proxies demonstrate that the climatic conditions were warm and humid during the Paleocene–Eocene thermal maximum (PETM) event. The PETM extended warm‐water episodes led to eutrophic conditions, which resulted in intensified subaerial weathering and nutrient mass influx, thereby contributing to rise in marine primary bioproductivity within the photic zone. Consequently, the high bioproductivity concomitant with active OM preservation promoted amassing of organic carbon in Patala shale facies during deposition of the Paleocene–Eocene time.
Ishaq et al. (Mon,) studied this question.