Northward drift of the Burma Terrane with India during the Cenozoic and implications for the India-Asia collision

Abstract

The past location of the Burma Terrane during the convergence of the Indian and Asia tectonic plates, is key for unraveling the regional geodynamic, paleoenvironmental, and paleobiogeographic history of the eastern edge of the Himalayan orogen. Paleomagnetic data provides the ability to constrain the Burma Terrane location, however, it has been very difficult to find rocks with paleomagnetic records of primary characteristic remanent magnetizations. We present here new paleomagnetic results spanning the Paleocene to late middle Eocene within the Burma Terrane, complementing paleolatitudes previously established from Late Cretaceous intrusive rocks and late middle Eocene sedimentary rocks. Our paleomagnetic data indicate that the Burma Terrane remained at equatorial latitudes during the Paleocene and early Eocene, at a considerable distance from the South Asian margin. In addition, paleomagnetic results from mid to late Eocene sedimentary rocks yield a predominantly north-south orientation of the Burma Terrane over the past 45 million years, showing that it was not part of the northwest-southeast oriented Sundaland margin prior to its collision with India. Our results support collision models involving a Trans-Tethyan subduction system during the Late Cretaceous and early Paleocene. We propose that this system incorporated the Burmese volcanic arc and continental fragments of Argoland before drifting north with India towards Asia. The new paleogeographic model considers a reduced amount of oblique subduction of the Indian Plate below Burma during the Cenozoic. A possible source of sediments filling the thick Myanmar basins from the Gangdese belt during the Eocene supports the hypothesis of an India-Asia collision around ∼50Ma. The new paleogeography supporting the formation of the Myanmar Cretaceous amber on an isolated Trans-Tethyan Arc is also a key element in discussions of the paleobiogeographic evolution of the numerous faunas it contains.