Effect of Deccan lava flows on the sedimentological evolution of Gurmatkal intertrappeans Karnataka, Southern India

Intertrappeans from the vicinity of Gurmatkal, northern Karnataka preserves its depositional and post depositional history during the Cretaceous-Paleogene boundary (KPg) interval. The deposits consist of chertified limestone and limestone successions. The carbonates are rhythmic and fossiliferous. The isotopic delta C-13 and delta O-18 values for carbonates are highly negative, which also show a strong correlation among them. The fossil assemblage includes bivalves, ostracodes, gastropods, insects, filamentous algae, and some plant twigs and leaves. The present studies signify fresh water, alkaline, closed basin lake in a terrestrial region. Marginal areas with minor fluctuations of shallow well-oxygenated lacustrine-palustrine settings are revealed from the sedimentological characteristics. Pre-, syn-, and post-sedimentation volcanic activity was prevalent in the area. The increased anaerobic conditions lead to rapid changes in the system. The presence of lateralized zone, red bole morphology, and pedogenized calcretes/silcretes, imply hiatuses between the sedimentation and the overlying lava flows.