Continent collision time estimated
doi:10.1038/nindia.2010.183 Published online 31 December 2010
Geologists have obtained, for the first time, a clear picture on the time of the prehistoric continent-continent collision between Asia and India. They say the collision took place before 53.7 million years ago.
This timing is considered controversial, but is generally thought to have occurred in the Early Eocene, around 50 million years ago (Ma).
The researchers have dug out new data from strontium isotopes, stable carbon isotopes, microfossil biostratigraphy, and mammal fossils from an Early Eocene marginal marine sequence (Cambay Shale) at the Vastan Lignite Mine of western India. The data indicates that terrestrial faunal exchanges, and therefore continental collision, between Asia and the Indian subcontinent took place before 53.7 Ma.
The researchers say this age coincides with the second Eocene Thermal Maximum (ETM2), a short-lived warming episode that followed the Paleocene-Eocene Thermal Maximum (PETM) around 55.5 Ma.
The new data also clearly records ETM2 in terrestrial organic material from a low-latitude site. The magnitude of the carbon isotope excursion (CIE) at this site closely matches that of marine cores from the Arctic Ocean. This, the researchers say, supports an interpretation that this hyperthermal event, though of lower magnitude, was similar in character to that of the PETM, being a global phenomenon that affected both terrestrial and marine ecosystems.
Authors of this study are from: University of Wyoming, Laramie, Wyoming and Northeastern Ohio Universities College of Medicine, Ohio, USA; Department of Earth Sciences, Indian Institute of Technology Roorkee, Institute Instrumentation Centre, Indian Institute of Technology Roorkee and Department of Geology, Lucknow University and Birbal Sahni Institute of Palaeobotany, Lucknow, India.
- Clementz, M. et al. Early Eocene warming events and the timing of terrestrial faunal exchange between India and Asia. Geology 39, 15-18 (2010)