Quantitative Radiolarian Assemblages in Surface Sediments from the Central Indian Basin and their Paleomonsoonal Significance

The percentage data of 47 radiolarian coarser taxonomic groups in the surface sediments from the central Indian Basin was subjected to cluster and factor analyses. The R-mode cluster analysis resulted in 3 dominant clusters which represent surface, subsurface and deep water dwelling radiolarian groups. The Q-mode factor analysis resulted into three dominant factors. The factor-1 is characterized by Pyloniids group dominating the southwestern part with higher salinity (>34.5/ppt), low sea surface temperature <27°C) and high potential primary productivity (>0.2 mgC/m³/h) during the southwest monsoon. The factor-2 is characterized by Spongodiscids group dominating the northeastern part with lower salinity <34.5/ppt). warmer SST (>28°C), and poor potential primary productivity <0.2 mgC/m³/h) during the southwest monsoon. The factor-3 is characterized by Euchitoniids group dominating a transitional area between the two factors.