Cluster analysis of benthic foraminiferal morpho-groups from the western margin of India reflects its depth preference

Abstract

Q-mode and R-mode cluster analyses have been carried out on the census counts data of 68 genera and one ‘other genera’ of benthic foraminifera from 32 stations off Mangalore-Cochin sector, west coast of India, to study the ecological preferences, especially the effect of depth on external test morphology of benthic foraminifera. We report that benthic foraminiferal distribution in the central western continental margin of India, can be grouped into three clusters. Cluster A is predominantly represented by angular-asymmetrical forms, cluster B is dominated by rounded-symmetrical forms, whereas cluster C includes both rounded-symmetrical and angular-asymmetrical forms. From the spatial distribution of cluster A-C-B, we report that with decreasing depth, there is a gradual tendency among benthic foraminifera to become more symmetrical from angular-asymmetrical. The observed morphological changes in benthic foraminifera are attributed to the sediment turbulence. The spatial distribution of benthic foraminifera indicates that the angular-asymmetrical morpho-group indicates relatively deeper water while rounded-symmetrical forms suggest shallow environment. Therefore, the temporal variation in the relative abundance of these benthic foraminiferal morpho-groups, can be used for paleo-depth reconstruction.