'Chail Series' of the Himachal Himalaya

Abstract A critical study brings out that the 'Chail Series' broadly occurs in two tectonic positions - the 'Lower Chail allochthon' as a thrust sheet over the Shali and the' Upper Chail allochthon' as an infra-Jutogh thrust sheet. The revision mapping of the Simla area has brought out that the' Lower Chail allochthon' includes (i) a sedimentary unit occurring as a cover over the Shali and designated as the Basantpur Formation of the Simla Group and (ii) a regional nappe tectonically overlying the Shali-Simla Groups and designated as the Salkhala thrust sheet. The' Upper Chail allochthon' has been found to be part of the Jaunsar Group. Thus, the' Chail ' was never an entity and has lost its validity as a stratigraphic term. This naturally precludes its adoption even as a tectonic term.