Evolution of the Himalayan foreland basin, NW India

This paper provides new information on the evolution of the Himalayan foreland basin in the under-reported region of the Kangra and Subathu sub-basins, NW India. Comparisons are made with the better documented co-eval sediments of Nepal and Pakistan to build up a broader picture of basin development. In the Subathu sub-basin, shallow marine sediments of the Palaeocene-lower Lutetian Subathu Formation are unconformably overlain by the continental alluvial Dagshai and Kasauli Formations and Siwalik Group. The start of continental deposition is now dated at younger than 31 Ma from detrital zircon fission track data, thereby defining the duration of this major unconformity, which runs basin-wide along strike. Final exhumation of these basin sediments, as thrusting propagated into the basin, occurred by 5 Ma constrained from detrital apatite fission track data. In the Kangra sub-basin, the Subathu Formation is not exposed and the pre-Siwalik sediments consist of the Dharamsala Group, interpreted as the deposits of transverse-draining rivers. In this area, there is no evidence of westerly axial drainage as documented for coeval facies in Nepal. Similar to data reported along strike, facies analysis indicates that the sediments in NW India represent the filled/overfilled stages of the classic foreland basin evolutionary model, and the underfilled stage is not represented anywhere along the length of the basin studied to date.