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Thamban, M.
- Distribution of Organic Matter, Iron and Manganese in the Estuarine Clay of Mangrove Sediments, Tellicherry, Kerala
Authors
1 Marine Geology Division, School of Marine Sciences, Cochin University of Science and Technology, Cochin - 682 016, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 48, No 2 (1996), Pagination: 183-188Abstract
The surficial mangrove sediments in the estuarine course of Eranholi river were sampled at 21 locations and analysed for the determination of organic matter, iron and manganese in 2 mm size fraction of the sediments. The study indicated that the these constituents are apparently controlled by the spatial variation of the physico - chemical factors of the estuary such as pH and Eh, base exchange and adsorption characteristics and the texture of the sediments, tidal influence and proximity to the mangrove vegetation in the prevailing estuarine environment.Keywords
Geochemistry, Marine Sediments, Mangrove Environment, Tellicherry, Kerala.- Dune Associated Calcretes, Rhizoliths and Paleosols from the Western Continental Shelf of India
Authors
1 National Institute of Oceanography, Dona Paula - 403 004, Goa, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 49, No 3 (1997), Pagination: 297-306Abstract
The calcareous deposits on the western continental shelf of India, off Bhatkal (water depths 50 to 58 m) occur as crusts, sheets, cylinders and reddish brown mudstones. The outer layers of the crusts are micrite-dominated and beneath this layer detrital/carbonate sands with thin heavy mineral laminations are found. Textural studies indicate that the detrital sands are derived from dunes. Drusy calcite and neomorphic calcite cements are associated with the sands. Sheet deposits contain coarse calcareous component-dominated layer within micrite layers and abundant micrite cements. These are similar to dune associated calcretes.
Cylinders are rhizoliths and show different stages of ischolar_main calcification. Circular bodies. about 0.15 mm to 0.70 mm diameter, interpreted as vascular cylinders of the ischolar_main tissues are typical. Radial fibrous calcite and spar calcite with inclusions indicate neomorphic cements. Reddish brown mudstones contain calcified ischolar_main-hair sheaths, micrite glaebules and reworked pollen suggesting that these are indurated soils. X-ray diffraction studies indicate the presence of ferroan calcite, quartz, pyrite and dolomite in rhizoliths and ferroan calcite, goethite and quartz in mudstones. Mudstones and some rhizoliths are Fe-rich and some other rhizoliths are Fe-poor but enriched with Mg and Mn. The particulate matter in the calcareous deposits were initially at the proximity of the coast and cemented by metastable calcites during the ultimate Pleistocene interglacial sea-level stands on the shelf. Pedogenic cementation processes overprinted and developed them into eolianites and paleosols during the subsequent Late Pleistocene sea-level regression. The compositional differences of these deposits were apparently controlled by type of sediments and associated sedimentary environments.
Keywords
Sedimentology, Calcretes, Rhizoliths, Paleosols, Continental Shelf.- Clay Mineral and Textural Variations in the Sediments of Chandragiri River, Estuary and Shallow Marine Realms off Kasaragod, Kerala
Authors
1 Department of Geology, Government College Kasaragod, Vidyanagar, Kasaragod - 671 123, IN
2 National Centre for Antarctic and Ocean Research, Department of Ocean Development, Headland Sada, Vasco da Gama 403 804, Goa, IN