Fluvial architecture during Late Pleistocene in the Southern Ganga Foreland Basin: Implication to Peripheral Bulge Tectonics

Thrust loading of continental crust along the north margin of Indian plate produced a flexural foreland known as Ganga foreland. Sedimentation in this basin is controlled both by Himalayan thrust and by peripheral bulge... [ view full abstract ]

Thrust loading of continental crust along the north margin of Indian plate produced a flexural foreland known as Ganga foreland. Sedimentation in this basin is controlled both by Himalayan thrust and by peripheral bulge tectonics. The Late Pleistocene deposits of the modern foreland are well preserved in the Southern Ganga plain and provide opportunity to understand (i) its late Pleistocene fluvial architecture (ii) the impact of peripheral bulge tectonics on the sedimentation. In the proximity of its peripheral bulge, deeply incised cliff sections exposed along the Yamuna, a Himalaya bound river archive 15-30 m thick sequences of sediments derived from craton and Himalaya. We present data on sedimentary lithofacies, paleocurrent, and chronology on these sequences and attempt evaluate the role of peripheral bulge tectonics in its evolution. Studied sections helped reconstruct a regional pedogenic surface at the base, which, besides field based observations, is confirmed using geochemical proxies (CIA) and clay mineralogy. This horizon is seen traversed by conjugate set of calcrete filled fractures. Sitting unconformably on this is unit of a cratonic sourced large scale cross bedded gravel and the occurrences and paleocurrent data from these gravel bodies indicate propagation of the gravelly fans from peripheral bulge. This unit also yielded a fossil skull of elephant (elephas namadicus) and several vertebrate fossils, molar fragments. The luminescence age of this units ranges from 100-60 ka making paleosol >100 ka. The age of the uppermost youngest horizon of cliff sections is 11 ka. We believe that the paleosol horizon marks the tectonic activity along the peripheral bulge which is followed by a wet and warm climatic conditions depositing gravels sourced from already uplifted peripheral bulge between 100-60 ka. This is youngest record of tectonics along the peripheral bulge of the Ganga foreland and similar type of bulge related sequences are reported from the Cenozoic Siwalik and Taiwan foreland successions.