Abstract:
The Eocene redbeds unit of the Western Himalayas Foredeep basin are critical in two aspects: first, it is the oldest Teriary sequence containing detritus unequivocally derived form the incipient Himalayas and secondly, it contains a diverse fauna key for understanding the evolution of several modern mammal groups. This sequence is known as the Kuldana formation in the Kohat-Potwar region (=Upper Indus Basin) and the Upper Subathu formation in Kashmir and Himachal Pradesh. This paper focuses on the lithostratigrpahic details of the Kuldana Formation from the Kala Chitta Range (Kohat-Potwar region), which also has yielded the best Eocene mammalian fauna in the region. It is a mudstone dominant unit, mainly red to purple in the Lower Kuldana but green in the Upper Kuldana. The Lower Kuldana also contains channel sandstone, immature paleosols and fresh-water limestone with molluscs (Planorbis) and algae (Chara), suggestive of terrestrial deposition regime with shallow channels, ephemeral lakes and wide floodplains. The Upper Kuldana has relatively thicker limestone interbeds with common oysters and rare benthic formainifera, indicating return to marginal and shallow marine environment as existed before the onset of Kuldana Formation. This marine transgression, correlated with the early Lutetian highstand, deposited the overlying limestone-dominant Kohat Formation. The Kuldana-Kohat couplet was restricted to the Kala Chitta and Kohat regions whereas the rest of the Western Himalaya foredeep turned into a lowland deposition. The shift from marine to terrestrial environment as witnessed in the Kuldana/Upper Subathu sequence is related to early Eocene Himalayan orogeny, when the incipient Himalaysas became highland and started shedding sediments to the Foredeep basin. By early late Eocene, the Neotethys drained out from the Paleogene foredeep and shifted to the Katawaz-Makran basin in the west, which then was the main depocenter for the sediments shed from the Himalayan orogene highlands. These tectonic events produced a chain of highlands along the north and western margin of the Indian plate, providing filter bridges for dispersal and migration of mammals to and from South Asia. The Eocene mammalian fauna from the Foredeep and also from the Ladakh basin is a curious blend of some endemic and a few mirgrants of Eurasian and North American affinities.
Page(s):
83-104
DOI:
DOI not available
Published:
Journal: Geological bulletin (university of peshawar), Volume: 34, Issue: 1, Year: 2001