Long-term palaeoecological trends of the Late Cretaceous bivalves from Ariyalur, India

The present study aims to investigate the change in the bivalve community in the Late Cretaceous of the Ariyalur Sub-basin, south India, along with the changing sea level, depositional sequence, and lithology. A drop in bivalve diversity was recognized from the siliciclastic facies of the Coniacian-Santonian to the carbonate facies of the Maastrichtian. Two-way cluster analysis identified five distinct bio-assemblages and a prominent shift in the dominant ecological guild. The Coniacian–Santonian assemblages are dominated by infaunal taxa that changed into epifaunal-dominated Maastrichtian assemblages. Although the effect of secondary diagenetic alteration might have played a role, non-metric multidimensional studies suggest that other factors, especially the change in substrate condition and corresponding adaptive strategies employed by different functional groups of bivalves, may potentially explain the shift in community structure across the studied interval.