The Ediacaran Salt Range Formation (ESRF) (<551 Ma) is a key Precambrian source rock horizon in the Potwar Basin (PTB), with high TOC content range from 1.17 to 36.16 wt.% and predominantly composed of Type-I kerogen with early thermal maturation. This study analyzes ESRF source rocks and Paleozoic oils from two different PTB fields by means of gas chromatography-mass spectrometry (GC-MS) and carbon isotope analysis to evaluate geochemical heterogeneity and evaluate potential oil–source correlations. Integrated molecular markers and stable carbon isotope data, and multi-parameter correlation heat map with dendrogram analysis, show that the Paleozoic crude oils from both fields were originated from a common source within the basin. However, the results demonstrate no genetic correlation between these oils and the ESRF source rock. The geochemical parameters such as Pr/Ph, G/C 30 H, sterane/hopane, C 26 TT/C 25 TT, C 31 R/C 30 R, and the distribution of C 27 –C 29 steranes, as well as C 21 TT%, (C 19 +C 20 )TT%, and C 23 TT% combined with highly negative carbon isotope values (average −36‰), exhibit that the ESRF source rocks were deposited under highly saline, restricted marine conditions marked by anoxic water column stratification and predominantly algal-derived OM inputs. While, the Paleozoic crude oil samples exhibit distinct biomarker patterns and significantly less negative isotope values (average −21‰), signifying a distinct origin from typical marine Type II kerogen, formed under suboxic conditions with significant input from plankton and algae. Thermal maturity indicators, including C 29 20S/(20S + 20R), ββ /( αα + ββ ), MPR, MPI-I and the calculated vitrinite reflectance, indicate that the oils were formed from source rocks exhibiting higher maturity levels compared to the ESRF. The overall biomarker distribution and carbon isotope data suggest that ESRF source rock has comparable geochemical similarities with those of producing Precambrian oil from Karmupur-1 (Pakistan) and Baghewala-1 oil (India) and Huq super group in Oman.
Ali et al. (Wed,) studied this question.