Late Quaternary History of the Ganga Plain

摘要: Flexural subsidence of the Indian lithosphere created Ganga Plain foreland basin in front Himalayan orogen, which attained its present configuration during late Quaternary. Climate change, neotectonics and base level changes influenced evolution landforms Plain. The regional geomorphic surfaces are: (1) Upland Interfluve Surface (T 2 ); (2) Marginal (MP); (3) Megafan (MF); (4) Piedmont Fan (PF); (5) River Valley Terrace 1 ) (6) Active Flood plain 0 ). is widespread reference surface; other are either incised or overlie this surface. Formation these essentially related to climate cycles Pleistocene-Holocene (128 ka BP). These depositional have a succession overlying sediments, younger than time formation respective surfaces. sediments coming from Himalaya undergo significant chemical weathering alluvial where much Na, Ca, Sr, K, Mg, removed; while As, Cr, Ni Th enriched. In suitable conditions smectite kaolinite formed. partly eroded transported delta region beyond. consists large number river systems; originating different parts Himalaya, Peninsular Craton, formed at times Pleistocene-Holocene. runoff groundwater main sources water. It difficult make meaningful scheme classification channels. Based on sediment-water transfer patterns, channels classified into three broad categories. systems stages evolution. active perennial rivers within alluvium, show avulsion scale 10 4 -10 5 years; some channels, part ancient anastomosing network, act as flood years. exhibits microgeomorphic features helped reconstruction history last ∼20 BP: 20-13 BP - new drainage low density; 13-8 extension system, high rainfall; 8-6 channel disruption due base-level rise tectonics lakes retained most water-sediment T -Surface; 6-4 dry climate, increased terrigenous clastic lakes; 4-2 siltation lakes, moderate 2-0 fragmentation drying strong anthropogenic influence. tectonism, mostly form contractional system piedmont zone, prominent extensional southern basin. One events 8-5 BP, produced areas centripetal drainages changed fluvial landscape ponds with few grounds. was by change humid around BP.