Paleogene island arc collision-related conglomerates, Yarlung–Tsangpo suture zone, Tibet

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Abstract Coarse clastic rocks in the Liuqu Conglomerate, formed in both terrestrial and subaqueous settings, record a Paleogene phase in the tectonic evolution of Tibet. Facies changes are commonly abrupt with rapid changes in clast types, grain size and stratal patterns. Sediments were derived from the leading (northern) edge of the Indian margin and a Late Jurassic–Cretaceous intraoceanic island arc that lay within Tethys. The coarse clastic sedimentary rocks of the Liuqu conglomerates are extremely proximal, but are locally offset relative to their original source terranes. They record aspects of the history of collision between these terranes and are interpreted to have been deposited in oblique–slip basins that developed along the zone of collision. The absence of clasts derived from terranes to the north of the Yarlung–Tsangpo suture suggests that basins associated with deposition of the Liuqu Conglomerate developed prior to the final collision between India and Asia.