Veil lifted on Assam’s geological history; study finds evidence of an ancient sea.
Lumami: Researchers at Nagaland University have carried out a detailed geological investigation of Sylhet Limestone in the Dillai Parbat area of Assam’s Karbi Anglong district, offering new insights into how the rocks formed during the Eocene period in Northeast India.
The study, published in the peer-reviewed Journal of Geosciences Research, examines the depositional environment of the limestone and contributes to the understanding of carbonate sedimentation, palaeoenvironmental reconstruction, geological correlation and basin analysis in the region.
The research was conducted by Prof. S. K. Srivastava of Nagaland University’s Department of Geology and research scholar Tsenchumo Lotha from the same department.
Earlier studies of Sylhet Limestone had largely relied on limited datasets and field observations. The latest research used an integrated approach combining field observations, petrographic analysis and micropalaeontological investigations.
The researchers examined limestone, shale and sandstone layers, as well as physical and biological sedimentary structures. They also analysed microfossils, including foraminifers, and studied the mineral composition of the rocks through microscopic examination.
Based on the findings, the researchers said the area was once part of a shallow, warm marine environment with sufficient oxygen and nutrients to support marine life. The conditions were comparable to a lagoon or a near-shore shallow sea setting under a tropical to subtropical climate.
The study also suggests that sea levels fluctuated over time and that the depositional environment experienced varying energy conditions. Storm activity, the researchers said, produced distinctive patterns in the rocks.
The findings contribute to scientific understanding of sedimentation processes, microfossil assemblages and environmental conditions in Northeast India. The study indicates that the observed changes were linked to tectonic movements.
“We attempted to understand the depositional conditions by combining field observations and laboratory analysis. The evidence indicates that the limestone was deposited in a shallow marine, warm-water environment with favourable ecological conditions for microfaunal growth,” Prof. Srivastava said.
Lotha said the connection between fieldwork and laboratory results was central to the research. “Things are not always clear when we are in the midst of fieldwork. But when we connected the same with lab results, the overall picture started becoming clearer. That process was really important for understanding the environment of deposition,” he said.
Congratulating the team, Nagaland University Vice-Chancellor Prof. Jagadish Kumar Patnaik said the study enhances understanding of Northeast India’s geological history.
“Such high-quality research reflects Nagaland University’s commitment to advancing knowledge through rigorous scientific inquiry and interdisciplinary collaboration,” he said.
