The Paleocene syncollisional deposits in Renbu, southern Tibet, China: New insights into the foredeep–wedge evolution of the Himalayan foreland

Understanding turbidites and olistostromes in the foredeep depozone is critical for deciphering foreland–orogenic wedge interactions. Despite the abundance of syncollisional deposits in the central Himalaya, current research lacks analysis of their depositional models in this context. Our study focuses on the Renbu Unit, a recently discovered Paleocene syncollisional deposits in Renbu, assessing its lithological composition, sedimentary environment, and provenance. The lower part of the Renbu Unit is characterized by fine-grained turbiditic sandstones, showcasing maximum depositional ages of ∼80 Ma. Contrarily, the upper part, composed of coarse-grained turbiditic sandstones, presents a maximum depositional age of ∼64 Ma. The sandstones sources vary from the recycled Xigaze forearc basin in the lower unit to the Gangdese arc in the upper unit. Hence, the lower Renbu Unit could equate to the Jiachala Formation, and the upper Renbu Unit could correspond to its eroded counterpart whose zircon geochronology fits the biostratigraphic data of the Jiachala Formation. This leads to a new depositional model suggesting near-contemporaneous deposition of the Zongzhuo mélange, Jiachala Formation, and the Renbu Unit in the foredeep, demonstrating events like the orogenic front's collapse and gravity flow deposition.