Synchronous Sedimentation in Gonjo Basin, Southeast Tibet in Response to India-Asia Collision Constrained by Magnetostratigraphy

The India-Asia collision has been the object of vigorous debate for decades, with ages of the start ranging from Late Cretaceous to Oligocene. Sedimentary records preserved in both near-field and far-field settings provide critical evidence concerning the age and mechanism of the collision. Gonjo Basin, one of a series of fault-controlled basins developed along the eastern margin of Tibetan Plateau, contains well-exposed sedimentary successions, providing great potential for understanding depositional, tectonic-geomorphological and climatic history associated with India-Asia collision and plateau uplift. Lithofacies analysis reveals that the sequences consist of sandstone, mudstone and conglomerate, formed in fluvial-lacustrine systems. High-resolution magnetostratigraphy, constrained by U-Pb dating of zircon from a volcaniclastic layer which has been found in the central Gonjo Basin for the first time, indicates that sedimentation started at 69 Ma and continued in this locality until 50 Ma. Anisotropy of magnetic susceptibility (AMS) interpretation based on the age framework reveals a post-depositional compression after 50 Ma, responding simultaneously to the early uplift of southeast Tibetan Plateau driven by India-Asia collision