Episodes 2020; 43(1): 404-416
Published online March 1, 2020
Copyright © International Union of Geological Sciences.
O.N. Bhargava and Birendra P. Singh*
Department of Geology (CAS), Panjab University, Chandigarh 160014, India
Correspondence to:Email: firstname.lastname@example.org
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Rifting during the late Precambrian created the Tethyan basin in which the sedimentation continued up to Middle Cambrian (Cambrian Series 3). Onset of the late Cambrian- lower Ordovician Kurgiakh orogeny terminated the sedimentation and also deformed the late Precambrian and Cambrian sediments.
A shallow marine transgression during the lowermiddle Ordovician resumed the sedimentation with a prominent conglomerate horizon. The conglomerate horizon is absent in the Byans (Kalapani) and Bhutan sectors. The lower Ordovician siliciclastic sediments are succeeded by siliciclastic-algal-coral buildups during the Katian, indicating deepening of the basin; at this juncture the Bhutan and Byans areas too were submerged.
There was another subaerial break around the Wenlock, which extended up to the early Devonian. Shallow sea returned in the early-middle Devonian, manifested by the Muth Formation in the western Himalaya. The sea level relatively rose in the Givatian, heralding the siliclastic-carbonate sedimentation that continued upto the Tournaisian. In majority of the areas, there is a hiatus at the end of the Tournaisian. In the distal parts of Spiti-Zanskar sub-basin and Kashmir, however, the sedimentation continued up to Visean/ Serpukhovian. In Spiti-Zanskar, a late Carboniferousearly Permian diamictite horizon is present. The diamictites are assigned glacial origin by many workers.
The areas where the sedimentation had ceased during the Tournaisian, witnessed a marine transgression during the Asselian-Sakmarian. It was followedby outpouring of the 289 Ma Panjal Volcanics in parts of Kashmir, Zanskar and Lahaul. The 289 Ma interval represented by abreak between the Sakmarian and the Wuchiapingian sediments in the areas where the Panjal volcanics are absent. The Wuchiapingian transgression was extensive; it covered the Tandi, Chamba and Bhadarwah areas also.
Save Kashmir, the Changhsingian is absent in the Tethyan Himalaya and there is a marked hiatus between Wuchiapingian and the Induan. The Induan-Lias succession is characterized mainly by carbonate sediments throughout the Tethyan sector. The sedimentation ceased towards the Lias; the hiatus spanned the Late Oxfordian-Kimmeridgian.
The Kimmeridgian transgression, barring Kashmir, covered the remaining Tethyan sector. In the Cretaceous, the plate margin became active, thereafter the deeper water sediments were deposited in Spiti-Zanskar and Garhwal. With a Danian break, the Cretaceous sediments were succeeded by shallow marine Paleocene and the fresh water Eocene in Zanskar. Obducted ophiolite klippen were emplaced over the Cretaceous sediments in the Zanskar and Malla Johar areas. In Malla Johar the ophiolite has carried the deep water Triassic- Cretaceous sediments–termed as exotic blocks of Kiogad and Chitichun facies.