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Mumbai: A recent geological study has found out that the minerals found in the Saurashtra Basin dates back to Mesozoic era, spaning from about 252 to 66 million years ago. The study conducted by the Indian institute of Bombay and National Centre for Earth Sciences Studies Thiruvananthpuram has pieced together the region’s paleogeography revealing the paths of ancient rivers and the geological history of the Indian subcontinent.
In western India, spanning western Gujarat and the North of Mumbai coastline, lies the Saurashtra Basin which is an expanse of 2,40,000 SqKm area spanning sea and land. Much of the landscape here remains buried in volcanic rocks called Deccan Traps, created by volcanic eruptions at the Western Ghats during the Cretaceous period, 66 million years ago. However, the sediment beneath the volcanic ash and rocks hides the extraordinary journey of the Indian subcontinent over the millenia.
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A compelling study of the sediments of the Saurashtra Basin by the IIT Bombay and National Centre for Earth Science Studies reveals some secrets of the history of India and the ancient supercontinent configurations, providing insights into how continents were formed and have moved over time.
“Saurashtra Basin was formed by the separation of India from Madagascar about 100 million years ago. Before the separation, India, Madagascar, and the Seychelles were joined together. After the separation, the western margin of India became lowlands, while the north and north-eastern parts of the study area acted as highlands,” remarks Dr. Pawan Kumar Rajak from the Department of Earth Sciences, IIT Bombay and the lead author of the study
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Rivers flowing from the highlands of the north and eastern regions of the subcontinent brought along with them the sediments from these regions, depositing them in the low-lying Saurashtra basin. “The eruption of Deccan volcanism, which happened later, covered a vast area of the Saurashtra Basin, making it difficult to study the sediments. Today, only the mountains or hills, river sections and road-cuts expose the sediments of that time,” adds Dr. Rajak.
The study focuses on the ‘Mesozoic’ era sandstones in the Saurashtra Basin, that spans from about 252 to 66 million years ago. The team used electron probe microanalysis (EPMA) to determine the composition of minerals as well as the Uranium-Thorium age of a mineral and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) which allows to know the minerals' composition and ages on a small scale.
The new study showed that the sandstones in the Dhrangdara Group, northeastern part of Saurashtra Basin with 600 metres of thick sediment, primarily originated from two primary ‘Precambrian’ sources, the earliest part of Earth's history, covering most of our planet's timeline. Researchers found that the Neoproterozoic rocks, about 1 billion to 540 million years ago and Archean rocks, dating back from 4.5 billion to 2.5 billion years ago are the primary sources of the sediments in the Saurashtra Basin.
The team is looking to explore the minerals of the basin further to improve understanding of the geological history of the region. “The next plan is to work in the same area to refine our understanding of the source areas and paleogeographic changes of that time. We must check whether the sediments were also sourced from Madagascar and Seychelles. We plan to contact ONGC to get seismic data for the study area to determine the basin configuration and trace sediments across the Arabian Sea,” said Prof. Banerjee about future plans to continue the research.
