Himalayan Geology, Vol. 43 (1B), 2022, pp. 325-336, Printed in India
The Cambrian in the Lesser Himalaya
O.N. BHARGAVA*, BIRENDRA P. SINGH
Department of Geology, Panjab University, Chandigarh - 160014, India
*Email (Corresponding author): onbhargava@gmail.com
Abstract: We present lithostratigraphic correlations, paleocurrent analysis, general pattern of sedimentation, regional setup, tectonics, and the basin configuration of the Ediacaran-early Cambrian in the Lesser Himalayan zone (LHZ). The Ediacaran-early Cambrian sequences from the west to the east are preserved as the Hazira Formation in Hazara, and as the Tal Group in the Nigalidhar, Korgai, Mussoorie, Garhwal, and Nainital synclines. The age of these sediments based on acritarchs, small shelly fauna, brachiopod and trilobite ranges from latest Ediacaran to earliest Cambrian Series 2, Stage 4 (~512 Ma). Besides these, the Chilar (Himachal and Uttarakhand), Kerabari (Nepal) and Miri (Arunachal) of the latest Ediacaran age formed another basin south of the Hazira-Tal basin. The Tal basin extended in the west covering the Hazara region, turned south towards Bikaner-Salt Range and chased its own tail to form the Tethyan basin in the north. The overall thickness of the Tal sediments is maximum in the Nigalidhar Syncline, and the least in the Nainital Syncline; the Nigalidhar region formed the deepest part and the Nainital--the shallowest part of the basin.
There was a shallowing of the basin after the deposition of the Krol E dolostone, leading to deposition of clastics of the Earthy Siltstone Member (Shaliyan Formation, Tal group), as a result in shallower parts, the Earthy Siltstone Member was not deposited. The Chert Member marks flooding in subtidal/shallow anaerobic conditions; thereafter, the basin gradually further shallowed. The palaeocurrent directions in general are towards NE. The late Cambrian/early Ordovician Kurgiakh orogeny caused the obliteration and deformation of the Cambrian basin.
Keywords: Lesser Himalaya, Tal Group, Chilar Formation, Lithostratigraphic correlation Regional setup, Basin configuration, Tectonics
