Late Quaternary Evolution Of The Ganga Plains: Myths And Misconceptions, Recent Developments And Future Directions

Abstract

The Ganga Plains with their well preserved subsurface alluvial record form an important continental archive for understanding landscape development against a background of late Quaternary environmental changes driven mainly by Himalayan tectonics, palaeo-monsoonal dynamics, and base-level (related to sea-level) changes. For more than four decades, the Ganga Plains have been studied by fluvial geomorphologists and sedimentologists to understand landscape diversity and evolution and to generate climate proxy data through such archives as sedimentary facies, calcretes, palynomorphs, and clay minerals. The Ganga Plains are drained by rivers originating from the Himalaya and from the Indian Craton which join the north and south bank of the Ganga River, respectively. This has resulted in significant spatial diversity in sedimentation pattern, sediment composition and alluvial architecture of the Plains. In this study the issue of spatial diversity of the Ganga Plains is addressed through a scheme of classification that is based on (a) hinterland type and dynamics, (b) along-strike rainfall variability, (c) hinterland-basin connectivity, and (d) sea level influence. Such an approach centered on dynamics helps in understanding the relative stages of landscape development of the components of the Ganga Plains. Further, it allows for the assessment of inter-connections between components using a systems approach. A complex response of the alluvial system of the Ganga Plains to Late Quaternary climatic fluctuations is recorded in an east-west transect – the western part shows incised valleys and the eastern part shows a rapidly filling aggradational regime. From an analysis of the subsurface stratigraphic records of the Ganga Plains, geomorphic diversity in this transect is also interpreted from these Late Quaternary records.