Paleogeography of the India–Asia collision system
The paleogeography of the India–Asia collision system is the reconstructed geological and geomorphological evolution within the collision zone of the Himalayan orogenic belt. The continental collision between the Indian and Eurasian plate is one of the world's most renowned and most studied convergent systems. However, many mechanisms remain controversial. Some of the highly debated issues include the onset timing of continental collision, the time at which the Tibetan plateau reached its present elevation and how tectonic processes interacted with other geological mechanisms. These mechanisms are crucial for the understanding of Mesozoic and Cenozoic tectonic evolution, paleoclimate and paleontology, such as the interaction between the Himalayas orogenic growth and the Asian monsoon system,[1][2] as well as the dispersal and speciation of fauna.[3] Various hypotheses have been put forward to explain how the paleogeography of the collision system could have developed. Important ideas include the synchronous collision hypothesis, the Lhasa-plano hypothesis and the southward draining of major river systems.
India–Asia collision system
Timing of collision onset[edit]
Definition[edit]
The onset of continental collision is determined by any point along the plate boundary where the oceanic lithosphere is completely subducted and two continental plates first come into contact.[4] In the case of the India–Asia collision, it would be defined by the first point of disappearance of the Neo-Tethys oceanic crust, where the India and Asia continent come into contact with each other. Such process is defined by a point since the shape of continental margins is irregular. The complete consumption of the oceanic crust could occur non-synchronously along the collision front.[5]
Different methods can be used to constrain the age of collision onset. Commonly used geological evidences include stratigraphy, sedimentology and paleomagnetic data. Stratigraphy and sedimentology indicates the transfer of materials from one continent to another when two continents, meet, as well as the change in depositional environment after the oceanic basin is closed and sea water is completely expelled.[6] Paleomagnetic data indicates collision when the paleolatitudes of both continental margins overlap.[7]
The onset of the India–Asia collision has been poorly constrained from Late Cretaceous to Oligo-Miocene due to different interpretations of geological evidences by different researchers.[5]