CLAY MINERAL DISTRIBUTION IN BHIMUNIPATNAM-KALINGAPATNAM SHELF SEDIMENTS, EAST-COAST OF INDIA

Fiftyfive sediment samples from innershelf between Bhimunipatnam and K alingapatnam were analysed by X-ray diffraction for the composition an d distribution of clay minerals. In addition to seabed samples, residu al soils and fluvial sediments from hinterland were also studied. Smec tite, illite and kaolinite, in that order of abundance, constituted ch ief clay mineral groups in shelf sediments. Smectite zone is influence d mostly by the Godavari fiver derived from Deccan Traps and transport ed northward by longshore currents. Illite and kaolinite appeared to o riginate from coastal red sediments and by rivers Nagavali, Vamsadhara , Gostani, Nellimarla and Kandivalasa draining the Eastern Ghats. The conspicuous absence of chlorite and paucity of kaolinite in the shelf sediments suggested that the influence of the river-borne sediments fr om the north is negligible. Source rock and fluvial input influenced c omposition of clay minerals whereas northeasterly littoral drift influ enced distribution pattern of clay minerals.