Triple-stage India-Asia collision involving arc-continent collision and subsequent two-stage continent-continent collision

Abstract

The enigmatic geodynamic processes involved in the India-Asia collision shape our understanding of uplift and deformation of the Tibetan Plateau and the subsequent changes in the land-sea distribution pattern, monsoon-arid environments and biotic evolution in Central-Eastern Asia. However, the current geodynamic models dealing with the India-Asia collision history exhibit significant discrepancies in how, when and where exactly the collision of India with Asia occurred. Recently, we proposed a new hypothesis that favored the opening and closure of a North India Sea during the late Cretaceous to Paleogene. Here we present new additional paleomagnetic data from the red siliceous shales and cherts of the Sangdanlin Formation, which were deposited on the most distal continental margin of the Tethyan Himalaya terrane, i.e. the southern margin of the Neo-Tethys Ocean, during the middle Paleocene. The combination of our new and previously reported paleomagnetic data shows that the Tethyan Himalaya was at a paleolatitude of 14.1° ± 1.9°N during the interval 62.5–59.2 Ma and refines the maximum size of the North India Sea to about 2200 ± 500 km. Combining our geodynamic model with recently published paleomagnetic data from the Kohistan-Ladakh arc, we conclude that the India-Asia collision was a triple-stage process, which involved an arc-continent collision followed by a two-stage continent-continent collision. The arc-continent collision occurred at ca. 64 Ma between the Tibetan Himalaya (Tethyan Himalaya plus Greater Himalaya) and the Trans-Tethyan subduction zone at a paleolatitude of ~8°N. The initial continent-continent collision took place at ca. 61 Ma between the Tibetan Himalaya (plus the accreted Trans-Tethyan subduction zone) and Lhasa terranes at a paleolatitude of ~14°N. The final continent-continent collision occurred during 53–47 Ma between India and the Tibetan Himalaya, diachronously suturing the North India Sea from west to east. The triple-stage collision scenario is in agreement with the history of India-Asia convergence rates, and is reflected by the presence of three slab remnants below Tibet and India as documented by seismic tomographic imaging. Our updated collision scenario reconciles multidisciplinary evidence for the India-Asia collision and provides better constraints on the resulting paleoclimatic and paleoenvironmental changes in Central-Eastern Asia.