Geochronology and geochemistry of a sediment core from Bombay Coast

Abstract

Radiometric, mineralogical and compositional analyses of a sediment core from the continental shelf region off Bombay coast are reported. The 210Pb excess method yielded a sediment accumulation rate of 2.5mm/yr which is in agreement with accumulation rates observed elsewhere for shelf sediments. Mineralogically the clays are largely composed of smectite ( 60%). Chlorite and kaolinite are in very minor amounts ( 7%). Illite concentration is variable and increases with increasing age. This is related to the periodic fluctuations of illitic rich materials derived from the Indus river being washed southwards on to the shelf regions. Elemental concentration of certain major and trace metals (Al, Fe, Mn, Cu, Cr, Zn, Ni, Co, Pb) show that there is no regular pattern in the distribution of these elements with depth. Metal/Al ratios vary within a factor of 2 during the past 300 years