Restoration of Cenozoic deformation in Asia and the size of Greater India

Abstract

[1] A long-standing problem in the geological evolution of the India-Asia collision zone is how and where convergence between India and Asia was accommodated since collision. Proposed collision ages vary from 65 to 35 Ma, although most data sets are consistent with collision being underway by 50 Ma. Plate reconstructions show that since 50 Ma ∼2400-3200 km (west to east) of India-Asia convergence occurred, much more than the 450-900 km of documented Himalayan shortening. Current models therefore suggest that most post-50 Ma convergence was accommodated north of the Indus-Yarlung suture zone. We review kinematic data and construct an updated restoration of Cenozoic Asian deformation to test this assumption. We show that geologic studies have documented 600-750 km of N-S Cenozoic shortening across, and north of, the Tibetan Plateau. The Pamir-Hindu Kush region accommodated ∼1050 km of N-S convergence. Geological evidence from Tibet is inconsistent with models that propose 750-1250 km of eastward extrusion of Indochina. Approximately 250 km of Indochinese extrusion from 30 to 20 Ma of Indochina suggested by SE Asia reconstructions can be reconciled by dextral transpression in eastern Tibet. We use our reconstruction to calculate the required size of Greater India as a function of collision age. Even with a 35 Ma collision age, the size of Greater India is 2-3 times larger than Himalayan shortening. For a 50 Ma collision, the size of Greater India from west to east is ∼1350-2600 km, consistent with robust paleomagnetic data from upper Cretaceous-Paleocene Tethyan Himalayan strata. These estimates for the size of Greater India far exceed documented shortening in the Himalaya. We conclude that most of Greater India was consumed by subduction or underthrusting, without leaving a geological record that has been recognized at the surface.

Effects of upper mantle heterogeneities on lithospheric stress field and dynamic topography

“…This is evident from surface expressions of 5 different deformation processes around the globe, such as for example the ongoing crustal deformation processes that formed the Tibetan Plateau due to the continental collision of the Indian and Eurasian Plates (van Hinsbergen et al, 2011) or the rifting of the African Plate induced by its interaction with the Afar plume head (Ebinger and Sleep, 1998). It has been shown that shallow processes influence both the magnitude and orientation of the lithospheric stresses.…”

Insights on the kinematics of the India‐Eurasia collision from global geodynamic models

“…Unfortunately, paleomagnetic data alone places Lhasa anywhere between being south of the equator or in excess of 20 N in pre-collision times. However, equatorial or low latitude positions of Lhasa in the early Eocene would imply extreme post-collisional north-south shortening of the terrane, where only $290 km north-south shortening of the terrane is recorded in the geology from $100 to 20 Ma [van Hinsbergen et al, 2011b]. [25] In the region of Mt Everest, an initial high pressure and temperature metamorphic event at $39 Ma [Cottle et al, 2009] may be indicative of continent-continent collision between Greater India and Lhasa.…”

Geometry of the Pamir‐Hindu Kush intermediate‐depth earthquake zone from local seismic data

“…This collision, which initiated at 50-52 Ma [Patriat and Achache, 1984;Guillot, 2003;van Hinsbergen et al, 2011] and has led to the creation of world's highest mountain ranges and largest plateaux, is presently ongoing with a convergence velocity of 34 mm/yr near the western syntaxis [Molnar and Stock, 2009;DeMets et al, 2010]. The Pamir, a northwardconvex mountain range, has presumably been moving north relative to the surrounding regions since about 25 Ma [Sobel and Dumitru, 1997], overriding the Tajik-Yarkand Basin [Burtman and Molnar, 1993], which previously connected the Tajik Depression in the west and the Tarim Basin in the east.…”

“…[3] The western Himalaya-Hindu Kush-Pamir system accommodated a similar amount of Cenozoic convergence as the Himalaya-Tibet system, albeit over a much shorter meridional width, resulting in a higher amount of upper plate shortening [van Hinsbergen et al, 2011[van Hinsbergen et al, , deduce 1050 as well as a probably higher amount of crust that vanished into the mantle. Lithospheric deformation is accompanied by vigorous intermediate-depth (up to nearly 300 km depth) earthquake activity [Billington et al, 1977;Pegler and Das, 1998], which is, with the possible exception of Vrancea, Romania [Ismail-Zadeh et al, 2012], globally unique within a continental collision zone far from any active oceanic subduction.…”