Paleoecology of Bivalves from Lower Miocene of Kutch, India

Das, Shibajyoti (2015) Paleoecology of Bivalves from Lower Miocene of Kutch, India. Masters thesis, Indian Institute of Science Education and Research Kolkata.

PDF (MS dissertation of Shibajyoti Das (10MS06)) MS_Thesis_Shibajyoti_Das_10MS06.pdf - Submitted Version Restricted to Repository staff only Download (3MB)

Abstract

Shallow marine areas are extremely sensitive to sea level changes that are often caused by climatic fluctuations. Molluscan fauna of these settings possess a unique combination of accreting shells preserving climatic signature and a history of rapid ecological and evolutionary response to climatic shifts. The shallow marine deposits from Lower Miocene of Kutch, India provides an unique situation to reconstruct paleoclimate with a dominance of durable calcitic shells of Ostreidae that retains the original isotopic composition; hence, it is an ideal scenario to test the relationship between climatic shift and the biodiversity of shallow marine fauna. Our study primarily focuses on the shallow marine bivalve community from thirteen different localities representing two formations of Lower Miocene, namely, Khari Nadi formation (Aquitanian) and Chassra formation (Burdigalian). Previous works on global and local scale indicates a climatic shift towards higher temperature in Lower Miocene of India. The rarefied α diversity for the families of bivalves did not show any significant difference, however, the β and γ diversity between the two formations have shown a significant difference. Thus the total diversity and the community structure of the two formations are significantly different. We see a two fold increase in the dominance of Ostreidae from Khari Nadi to Chhasra Formation. Our study also focuses on the morphological change (body size) between the two formations. Three families of bivalves: Pectinidae, Ostreidae and Veneridae were studied for this purpose. Data suggests that there has been a significant decrease in the body size of two out of three bivalve families in the younger Chassra formation. Hence the results of this study indicate a bivalve diversity profile (taxonomic and morphological) that changed at the face of climatic fluctuations during Lower Miocene.

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