Provenance of Jurassic-Cretaceous Tethyan Himalayan sequences in the Thakkhola Section- Nepal, inferring pre-collisional tectonics of the central Himalaya

Abstract The Jurassic-Cretaceous (Upper Tethyan) flysch well exposed in the Thakkhola Section, Nepal, was deposited prior to the continent-continent collision between the Indian and Eurasian plates. This Tethyan Himalayan Sequence (THS) has preserved the extreme northern passive margin of the Indian plate with its direct deposition onto the eroded Precambrian rocks in the lowest part of this relatively continuous section. The clastic rocks of the THS, as they are useful to constrain the paleogeography and paleotectonics of the Himalayan Orogen. In this study, we report the petrography, detrital zircon U-Pb isotopic ages, and zircon trace element data for sandstone samples from the Upper part of a Triassic stratigraphic section. The mineral modal composition data indicates that these quartz-rich units were derived from recycled orogen. This is supported that the youngest zircons analyzed can be dated to ~400 Ma that predates the depositional age by hundreds of millions of years. A total of 85% of the zircon ages are