Source of Organic Matter and Paleo-Environmental Reconstruction 13 Using 8 C Isotope from Mid-Siwalik Sediments of a Late Miocene Himalayan Foreland Basin, Pakistan

Abstract

This study examined the stable carbon isotope13 (8 C) and characterization of sources of organic matter from core samples of sandstones of mid-Siwalik group Dhok Pathan Formation from Surghar- Shingar Range of NW Himalayan foreland Fold-and-Thrust-Belt. These sediments have recorded valuable information regarding the palaeo-vegetation type and paleo-environment/depositional environments. The analytical results of stable carbon isotope range from -24.50 to -28.43% with an average value of -26.56%. These values correspond to C3 vegetation of cool growing season and support the hypothesis of the dominance of C3 biomass in the ecosystem during the late-Miocene in this area. The phytoclasts are characterized as huminite/vitrinite, derived from terrestrial plants and referred to as type-III kerogen. The fungal attack, scaring and pitting of bacterial activity, biochemical degradation, replacement/diagenetic development of pyrite suggest that these sandstones of Dhok Pathan Formation were deposited under dyoxic conditions and thus these sandstones are primary reduced sandstones.