| Summary: | Grain size and clay mineral distribution up to 45 cm depth in the silty clay sediments from 26 box cores from 10 degrees to 16 degrees S along four longitudes (73.5 degrees-76.5 degrees E) were studied for understanding spatial variability in the Central Indian Basin (CIB). The average sand content in the basin is 3.8%, which decreases systematically and longitudinally to 0.3% towards south. The average illite and chlorite major clay mineral abundance also decrease southwards along the four longitudes from 10 degrees S, and show the limit of influence of the Ganges-Brahmaputra river's supply up to 10 degrees S. However, the average clay content increases from west to east in the basin, and southwards along 73.5 degrees E and either side of the 76.5 degrees E fracture zone (FZ), which strongly suggests the possibility of clay supply due to circulation of Antarctic Bottom Water from the south through the FZ. The distribution of four clay minerals along 73 degrees and 76.5 degrees E FZ in the CIB shows dissimilar trends of increase and decrease, and indicate a mix environment. The FZ in the CIB therefore has an important role in controlling the distribution of clay minerals.
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