V016-0010
Depositional Environment of the Jhilmili Intertrappean Section from the Deccan Province of Central India: A Geochemical Approach
Wednesday, 9 December 2020
Poster
Vandana Kumari, Indian Institute of Science Education and Research Bhopal, Bhopal, India, Nithin Kumar, Indian Institiute of Science Education and Research, Earth and Environmental Sciences, Bhopal, India and Arundhuti Ghatak, Indian Institute of Science Education and Research Bhopal, Department of Earth & Environmental Sciences, Bhopal, India
Abstract:
The Deccan Traps and associated sediments have evoked interest over several decades as they constitute one of the important LIP’s on the globe besides being known for having played a significant role in causing the “Cretaceous–Tertiary mass extinction”. The sediments coeval with Deccan traps, especially in central India, are most commonly recognised to have been deposited in fluviatile-lacustrine environments. At variance from these commonly occurring continental facies, a part of the 14m thick sedimentary sequence sandwiched between two flows in Jhilmili area (Chhindwara District, central India) has yielded Danian foraminifers. Based on this evidence, the existence of a Maastrichtian-Danian seaway in central India has been hypothesised. The 14m thick intertrappean sequence exposed in Jhilmili is mainly a non-marine section except for a 60 cm thin marly horizon which yielded planktonic foraminifers.
Against this background, we present preliminary geochemical analysis of Jhilmili intertrappean sediments, for gaining further insights on the depositional environments. The trace element analysis of bulk and clay fractions show relatively high concentration of Ba (41.7–647.5 ppm) than that of Sr (52.3–212.2 ppm) and variable Y/Ho ratios (22.7–33.6). Geochemical parameters such as Ba/Sr (>1) and Y/Ho (<50) ratio for these sediments are consistent with non-marine sediments. Further, carbonate fractions show a distinct REE+Y pattern with no LREE depletion ([Nd/Yb]PAAS ~ 1), negative La anomaly ([La/La*]PAAS = 0.1 to 0.6) and slightly negative Gd anomaly ([Gd/Gd*]PAAS = 0.6 to 0.7), which is significantly different from carbonates precipitated from sea water. The near chondritic Y/Ho ratio (~33) provides further support to the existence of non-marine depositional conditions. The traditional geochemical proxies indicate a non-marine depositional setting for the entire Jhilmili intertrappean section, including, anomalously so for the foraminifera bearing 60cm thin marl intercalation.
