Biostratigraphy and provenance analysis of the Cretaceous to Palaeogene deposits in southern Tibet: Implications for the India‐Asia collision

Abstract

AbstractUpper Cretaceous to Eocene marine sedimentary sequences of the Yarlung‐Tsangpo Suture Zone (YTSZ) provide critical constraints on the initial process of the India–Asia continental collision and the closure time of the Neo‐Tethyan Ocean. New sedimentological, petrographic, biochronological and detrital zircon age data of Cretaceous–Palaeogene strata from the southern margin of the YTSZ are reported in this study. Detrital zircons from the Lower Cretaceous Gyabula Formation are dominated by Archean to Cambrian U–Pb ages, indicating a likely source originating from the Indian continent. In contrast, zircon ages from the Palaeogene Jiachala Formation are predominantly younger than 200 Ma, with a major peak of ca. 76–187 Ma, which is consistent with a source from either an intra‐oceanic island arc system or the Asian continent. Sixty species of radiolarian fossils obtained from the Gyabula, Zongzhuo and Jiachala Formations provide a regional correlation with the Cretaceous Tethyan realm and Palaeogene low‐latitude biozonation schemes based on the Unitary Association method. The Palaeogene radiolarian zonation UAZ JP10 identified in the Jiachala Formation, when combined with existing absolute age models derived from the Deep Sea Drilling Project and Ocean Drilling Program, indicates an age of ca. 61.8–61.1 Ma. Integration of the biochronological and detrital zircon age data suggests that major changes in provenance occurred at the Indian continental margin, allowing an important timing constraint on the onset of collision to be placed no later than the Danian at ca, 61.8 Ma. This study highlights the significance of focusing on distinct sedimentary sequences in collisional orogens to reconstruct the timing and processes of continental collision events.