Late Cenozoic Himalayan foreland basin: Sedimentologic attributes

Abstract

Late Cenozoic fluvial stratigraphic records of the Himalayan foreland basin- the Siwalik Group between Rivers Ganga and Ravi were studied and reviewed to understand the responses of allogenic forcing at variable timeframe. The Siwalik succession represents an upward stratigraphic coarsening sequence which was initiated ~13 Ma and terminated and deformed by the Himalayan Frontal Thrust (HFT) at around 0.2 Ma. Fluvial architecture, composition and paleoflow patterns exhibits patial and temporal variations and characteristics of a large river that evolved around 10 Ma with southward propagating mountain front with large gravelly alluvial fans evolving after 5 Main the proximity of Main Boundary Thrust (MBT). Influx of boulder- to pebblesized clasts indicatesmajor surface uplift at around 5 Ma all along the Himalaya. This uplift is more widespread and responsible for the generation of much of the modern drainage system. The fluvial architecture reveals variation in temporal and spatial deposition style at million-year scale in response to variable hinterland topography, tectonics and climate. However, direct climatic signatures are not evident, although stable isotopic studies suggest variability at million-year scale, which was overwhelmed by tectonics.