Provenance and distribution of clay minerals in the sediments of the western continental shelf and slope of India
ABSTRACT The distribution of clay minerals from 156 surficial sediments of the western continental margin of India, ranging from 17 to 2000 m water depth, indicate that there are three principal sources of sediments. The illite and chlorite-rich assemblage derived from the Indus (Indus Province) is predominant in the continental margin sediments to the north of the Gulf of Kachchh. An assemblage of smectite with minor kaolinite, illite and chlorite, mostly derived from the Deccan Trap basalts (Deccan Trap Province), occurs all along the inner shelf from Saurashtra to Goa. Illite, however, dominates smectite in the outer shelf of Saurashtra and on the continental slope from Saurashtra to Goa. Some samples on the outer shelf of the Gulf of Cambay-Goa show trace contents of all clay minerals, while others from the same region show the dominance of smectite over illite. A smectite and kaolinite-rich assemblage with minor illite, chlorite and gibbsite derived from the Gneissic Province occurs both on the shelf and slope between Goa and Cochin.It appears that the Indus derived sediments are transported onto the continental slope and, to a lesser extent, the outer shelf of western India by a southerly surface current and admix with clays transported from the hinterland. The influence of the Indus borne sediments on the continental slope decreases from north to south and cross shelf transport processes dominate in the southwestern continental margin between Goa and Cochin.
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ABSTRACT: Clay mineral assemblages of the terrigenous fraction of 39 samples from ODP site 728A, located on the continental margin of Oman, northwestern Arabian Sea, have been analysed to understand the influence of sediment source, possible transport pathways and palaeoclimatic conditions during the late Quaternary. Illite, palygorskite and chlorite were the most dominant clay minerals, with minor amount of kaolinite and smectite. Quartz, plagioclase feldspar and dolomite were the other detrital minerals. The terrigenous content showed antithetic relationship with the biogenic carbonate, and was high during the glacial stages mainly due to low sea level and erosion of exposed continental shelf by wind and/or fluvial processes. The high biogenic carbonate during the interglacial periods has been correlated to intense monsoonal activity and surface productivity. The study suggests that the detrital minerals are largely aeolian derived from the adjoining Arabian Peninsula, Persian Gulf and Iran-Makran regions and transported to the northwestern Arabian Sea by northwesterly winds. It appears that the cold and dry periods during the glacial times were responsible for physical weathering and contribution of higher amounts of chlorite and dolomite. The warm and humid interglacial period caused extensive chemical weathering and contribution of kaolinite.
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ABSTRACT: The bulk concentration (wt%) and mass accumulation rates (MAR; g/cm sup(2)/ka) of terrigenous source representing elements such as Al, Ti, K and Zr in a sediment core (SK-129/CR-05) from southeastern Arabian Sea, record considerable variations in riverine sediment discharge over the last 140 ka. The mean Al concentration (4.51 plus or minus 0.47%) and its MAR (0.105 g/cm sup(2)/ka) are higher during the glacial period and lower (3.61 plus or minus 0.58%; 0.084 g/cm sup(2)/ka) in the interglacial period. This suggests an increased terrigenous sediment discharge (TSD) of approx. 25% corresponding with chemical weathering (K/Al ratio) during glacials than in the interglacials. The last approx. 5 ka received lowest and uniform TSD (mean Al concentration -2.36 plus or minus 0.06%; Al MAR, 0.075 g cm sup(2)/ka; K/Al ratio, 0.23 plus or minus 0.003) may be due to weak monsoon and stabilized sea level. Marine Isotope Stage (MIS) - and 4 recorded the lowest and highest TSD respectively. Interestingly, during MIS-5, interstadials (5.1, 5.3 and 5.5) were associated with relatively larger TDS, suggesting humid conditions and intense precipitation. On the contrary, stadials (5.2 and 5.4) were characterized by relatively smaller TDS, indicative of low precipitation and arid condition in the Indian subcontinent.
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ABSTRACT: of utilizable freshwater to be shared by Madhya Pradesh (65%), Gujarat (32%), Rajasthan (1.78%) and Maharashtra (0.89%). Gujarat, essentially both an agrarian and an industrial growth state, accounts for the following levels of India’s economic activities: industrial output 39%, mineral production 10%, salt production 80% (10.4 million tons per year), exports 20%, textile production 25%, pharmaceutical products 40% and petrochemical production 67%. However, Gujarat experiences recurrent droughts and spends nearly 40% of its domestic energy generation just to extract sufficient groundwater to meet its freshwater requirements. The unfettered development of industrial activities and unhindered labor exploitation in this state are attributed to the lack of bio-diversity, bio-resources and minimal social opposition (Khanna et al. 2000). To alleviate the freshwater shortage, Dr. Anil Kane, the former Vice-chancellor of M.S. University, Baroda, envisioned a mega-engineering project as ‘Kalpasar’ a reference to a mythological wish fulfilling tree (Kane 1995). Kalpasar is considered a harbinger of prosperity to Gujarat state by creating a freshwater reservoir