Abstract
Early Miocene-Pliocene Middle Siwalik Subgroup of Kuluchaur area, Uttarakhand, North India, comprises sheet-like, coarse to medium grained, cross bedded sandstone bodies and multistoreyed variegated mudstones. Paleocurrent study shows commonly unimodal and locally bimodal distribution and displays a high magnitude of resultant (R*=0.7337) oriented towards south-southwest (206° ± 42.27°). Palaeochannel morphological attributes suggest that the depositing river system was about 230 m wide and 4.5 m deep. These broad, shallow, and low sinuous channels with extensive flood plain flowed on a steeper slope (0.00043 degrees) with flow velocity of 60–140 cm/sec. It is visualized that the immature Middle Siwalik rocks were deposited by southward flowing braided rivers transverse to the Himalayas, predominantly in the form of overlapping alluvial fans similar to those depositing sediments at present in the Indo-Gangetic plains. Fairly consistent fluvial palaeoslopes, together with enormous thickness of sediments, are evidences of rapid subsidence of the basin. We conclude that the paleogeography of Indian subcontinent established at the onset of Miocene-Pliocene Siwalik sedimentation is continuing till today.
Highlights
The Siwalik foreland basin enclosing 5–8 km thick Late Cenozoic (Early Miocene to Pleistocene) fresh water fluvial sediments is a part of the marginal fold and thrust belt developed as a result of the continent-continent collision of Eurasian and Indian plates
Paleocurrent study reveals that the low channel sinuosity (? Braided) river, which deposited the sediments into the basin, advanced persistently from the north-northeast in a southsouthwest direction along a palaeoslope, which remained unchanged throughout the deposition of the Middle Siwalik sequence
The paleochannel estimates indicate that the Middle Siwalik basin was filled mainly transversely by southward flowing system of river, which were individually about 230 m wide and 4.5 m deep, originating from the Himalayas
Summary
The Siwalik foreland basin enclosing 5–8 km thick Late Cenozoic (Early Miocene to Pleistocene) fresh water fluvial sediments is a part of the marginal fold and thrust belt developed as a result of the continent-continent collision of Eurasian and Indian plates. The regional paleogeography of Siwalik foreland basin, especially the outlet of Siwalik Rivers, is still an open question. The present work concentrates on the Kuluchaur area of Uttarakhand, Northern India, central part of the Dehradun subbasin of the Himalayan foreland basin, exhibiting a thick sandstone-mudstone succession of Middle Siwalik in the NW Himalaya. This sequence extends laterally for >40 km between Ganga and Kosi Rivers (Figure 2).
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