抄録
Mineralogical studies of some Meghna Floodplains soils, in which the sediments as parent materials were possibly transported by the Meghna, Old Brahmaputra, Jamuna (Brahmaputra), and/or Ganges Rivers, were carried out to determine the contribution of different river sediments in Lower Meghna River Floodplain, Young Meghna Estuarine Floodplain, and the part of Old Meghna Estuarine Floodplain which is surrounded by Ganges Floodplains. In general, mica, smectite, vermiculite, chlorite and kaolinite were the major clay minerals in these soils. Soils of Lower Meghna River Floodplain were dominated by mica, vermiculite and chlorite, and were estimated to be developed from the Jamuna (Brahmaputra) sediments while the contribution of the Meghna/Old Brahmaputra sediments increased towards the surface. The Ganges sediments had apparently no contribution. In contrast, soils of Young Meghna Estuarine Floodplain contained good amounts of smectite and chlorite in addition to mica, and were estimated to be developed from the Ganges and Meghna/Old Brahmaputra sediments. Due to the predominance of smectite in the Ap and B horizons or Ap horizon, soils of the part of Old Meghna Estuarine Floodplain which is surrounded by Ganges Floodplains were estimated to consist of the Ganges sediments in the upper horizons and of the Meghna/Old Brahmaputrta sediments in the lower horizons.
