Images of possible fossil collision structures beneath the Eastern Ghats belt, India, from P and S receiver functions

Abstract

The Proterozoic Eastern Ghats belt of India is often believed to be the ancient analogue of the present-day Himalayas. However, geological and geophysical signatures that can be traced and linked to the Eastern Ghats belt orogen due to a Precambrian collisional episode are sparse and evidence of such a geotectonic process in the deep lithosphere remains elusive. Utilizing the P and S receiver function imaging technique, we present depth signatures of this convergence event and its lateral extent. Approximately 2000 P and S receiver functions that predominantly sample the Eastern Dharwar craton-Eastern Ghats belt reveal the presence of two distinct westerly dipping interfaces at depths centered on 150 km and 200 km in the study region. Drawing analogy from similar tectonic settings of Proterozoic age and younger Paleozoic times around the globe, we interpret these boundaries to represent remanent structures fashioned by the collisional processes that affected this region. Recent geological, geochemical, and geochronological evidence from the region strongly favors interpretation of our delineated dipping structures as possible vestiges of a Proterozoic collision event that are preserved due to their coherent translation with the overlying lithosphere. Due to this long-lasting record of Proterozoic tectonics, our results add a complication to simple models of the Indian subcontinent in which relatively thin lithosphere underwent rapid transit during the Cretaceous. © 2010 Geological Society of America.