Defining the expanse of Greater India: Insights from the Upper Triassic Langjiexue Group of northern Tethyan Himalaya

Knowing the size of Greater India is essential to constrain the geodynamic processes of India-Asia collision and Tibetan Plateau uplift, which, however, remains highly controversial, with existing estimates ranging from several hundreds (~400-950) to thousands (~1800-3000) of kilometers. Here, we report new paleocurrent measurements of the Upper Triassic turbidites (Langjiexue Group) from northern Tethyan Himalaya, supplemented with compiled provenance analyses, to help decipher the extent of Greater India. Well-preserved flute casts indicate mostly westward paleocurrents, suggesting a primary source located to the east (present coordinates) of the depositional area. In addition, compiled detrital zircon data reveal a similar east-west distribution, with samples exhibiting Australian-affinities (i.e., dominated by ~1170-1075 and ~575-530 Ma age populations) mostly found to the east of 91E°, whereas samples showing Indian-affinities (i.e., dominated by ~980-860 and ~565-505 Ma age populations) are generally limited to the west of 92E°. Importantly, the Langjiexue Group is characterized by a dominant age population of ~280-220 Ma (peak at ~238 Ma) with bimodal zircon ε_Hf(t) values (peaks at ~–1.2 and +6.8), matching well with those of coeval magmatic/sedimentary records in West Antarctica, but differing from those in eastern Australia, the Bird’s Head region, and the Lhasa terrane. Considering similar age patterns found in the Exmouth Plateau (NW Australia), we infer a large-scale transcontinental sediment transport pathway for the Langjiexue Group, which originated from West Antarctica, passed through West and NW Australia, and ultimately deposited offshore along northern (Greater) India in the Late Triassic. Therefore, the eastern margin of Greater India most probably reached to the Exmouth Plateau, implying an extent of ~1950 ± 260 km in the Late Triassic. This consideration is consistent with the recent estimate of ~1950 ± 970 km based on Early Cretaceous paleomagnetic data from eastern Tethyan Himalaya.