Picture credits: Siddharth Kankaria
Scientists from Indian Institute of Science, Bangalore, Indian Statistical Institute, Kolkata, Tokyo Institute of Technology, Japan and University of Michigan, USA trace the path of the Indian subcontinent on its journey to its current position.
Around 150 million years ago the Indian subcontinent along with Australia, Africa and Antarctica formed the supercontinent called Gondwanaland. 150 million years ago, however, the Indian subcontinent is said to have drifted north as an isolated land mass until it reached its current position around 55 million years ago. The subsequent collision with the Eurasian subcontinent led to the formation of the spectacular Himalayan-Tibetan system. Although the migration of the Indian plate is widely accepted based on geophysical, biological and geochemical signatures, large discrepancies still exist in its exact position during the transit and the rate of migration. A collaborative effort from researchers from around the globe was required to identify the exact path taken by the Indian subcontinent.
Now, a team of researchers from the Centre for Earth Sciences and Divecha Centre for Climate Change at IISc, Geological Studies Unit at Indian Statistical Institute, Department of Earth and Planetary Sciences at Tokyo Institute of Technology and the Department of Earth and Environmental Sciences at the University of Michigan have come together to track the migration of the Indian plate. According to Prof. Prosenjit Ghosh, an Associate professor at the Centre for Atmospheric and Oceanic Sciences “Our group has carried out a study to identify the sensitivity of isotopic composition of soil carbonates to ascertain position of Indian plate through time. The novel geochemical tool known as a clumped isotope palaeothermometer is used for this purpose”.
Samples of soil carbonates deposited in sequences of sediments from present day Narmada river valley were collected and analyzed. “The analytical results yielded information about temperature and meteoric water composition at the time of carbonate formation for the time period of 270 to 65 million years back. The well preserved geological archive served as book chapters. On investigation, we were able to trace out the air temperature and oxygen isotope compositions for the period between 270 million years to about 68 million years ago” explains Prof. Ghosh. And since the variation of the isotopic composition of rainwater is related to the latitudinal position, the team were, with some uncertainty, able to track the path taken by the Indian plate.
The new method not only performs as a new proxy for determining the latitudinal positions of plates but can also be used to find other features. “Our finding also implies that the global-scale hydrological cycle was not fundamentally different during these time scales i.e. late Paleozoic and Mesozoic. The new approach also revealed that the rate of movement of the Indian plate varied considerably during the entire journey” says Prof. Ghosh.
Currently, we can track the movement of the tectonic plates with great accuracy using Global Positioning Systems. But decoding the past movements of these plates has been a challenging task. The current study aims to enable researchers to not only track these past movements but also analyze other features of the earth from times gone by.