Stratigraphical evidence for glacial-interglacial sea-level changes in the Indian Ocean: Projection to the Antarctic ice sheet dynamics

Sedimentary profiles in Sri Lanka capture evidence for the regional and global-scale long-term climatic transition (e.g. K-Pg boundary mass extinction, Late Paleocene Thermal Maximum, Eocene–Oligocene climate transition, the growth of the Antarctic ice sheets) during its northward voyage from Gondwana to Asia. However, a glacial-interglacial climatic transition is not studied yet in Sri Lanka, and is poorly resolved in the Indian Ocean. Consequently, this ongoing research project is aimed to (i) reconstruct glacial-interglacial sea-level changes and (ii) identify its teleconnection to the Antarctic ice sheet dynamics. Sri Lanka has few recorded seismically driven tectonic activities and a low tidal range (about 0.5 m) making it suited for interglacial sea-level studies. The continental shelf along the south and southwest coasts of Sri Lanka is narrow and it is among the steepest continental slope in the world. However, several sea cliffs along the northwest and southeast coasts of Sri Lanka can be used to reconstruct interglacial sea-level changes in the central Indian Ocean. Here, several sedimentary profiles (i.e. deepwater Mannar Basin  and sea cliffs at Point Kudrimalai in the Wilpattu National Park,  Bundala and Patirajavela cliffs, and Ussangoda cliff) were examined to identify stratigraphic variations. Results show that carbonate burial drastically increased (average = 40.2%) in the Mannar Basin sediments from the Late Paleocene (close to the Paleocene–Eocene boundary). This observation can be linked to the movement of the Indian plate (including Sri Lanka) northward into equatorial latitudes and/or the growth of the Antarctic ice sheets by the sharp decline of atmospheric CO₂ concentration. The Miocene limestone in the northwest of Sri Lanka has also suggested the global cooling trend. Nevertheless, sea cliffs along the northwest and southeast coasts of Sri Lanka provide sufficient sedimentological evidence for the interglacial highstands. The Uranium–Thorium ages of marine shells in near-coast sites in India are dated to ca. 124.0–112.0 ka. It suggests that sea-level rose about 6–9 m to the present level during the Eemian interglacial period. The association of cross-bedded sandstone with calcrete in the upper beds shows a terrestrial dune environment after a relative sea-level fall during the glacial period. Consequently, the preliminary stratigraphic observations concluded that sea cliffs in Sri Lanka can be identified as promising sites to study teleconnection between glacial-interglacial sea-level changes in the Indian Ocean and the melting history of Antarctic ice sheets.