Landscape evolution of the Ganga-Sai interfluve in response to river dynamics and Late Pleistocene-Holocene climate change via a meander cut-off lake of a plains-fed channel

Abstract

The floodplains in the interfluve between the Ganga and Sai rivers in the Central Ganga Plains exhibit a broad suite of geomorphic features such as a linear array of meander cut-offs and oxbows representing abandoned sinuous channels. Here we integrate regional and local scale geomorphic analysis using satellite imageries with detailed chronostratigraphic and paleoclimatic reconstruction from a large oxbow lake (Baraila Tal) in the paleochannel belt to infer landscape evolution in this region. The stratigraphic succession at Baraila Tal supported by sedimentology and stable isotope composition of organic matter and micro-gastropod shells suggests that the lake was previously a part of an active fluvial system, and the depositional environment transformed from a fluvial to a lacustrine system in response to geomorphic and climatic changes during the post-LGM period. Integrating geomorphic and paleoclimatic data, we identify four stages (I-IV) of landscape evolution in the Ganga-Sai interfluve region during the Late Pleistocene-Holocene interval: (I) active channel phase of paleo-Sai river before 12 kyr, (II) development of paleochannel belt and meander cut-offs during 12–8 kyr, (III) development of ‘misfit’ Sai river and gullied landscape during 8–7 kyr, and (IV) expansion of ephemeral lakes (wetlands) and subsequent filling post 7 kyr. We have demonstrated the use of paleoclimate and paleovegetation data retrieved from a meander cut-off lake for deciphering landscape evolution.