Evolution of Ramasetu region as a link between India and Sri Lanka during the late Pleistocene and Holocene

Abstract

High-resolution seismic data of the Ramasetu region revealed three subaerial unconformities S1, S2, and S3. S1 is the youngest subaerial unconformity, whereas S3 is the oldest. These subaerial unconformities have been determined based on the presence of channel-incision signatures. Identified buried channels originated in the Palk Strait and debouched in the Gulf of Mannar. Youngest buried channels became most active during MIS 3 (~60-29 ka) and were buried entirely at ~7.0 ka. The study suggests that the Palk Strait evolved as a large multi-centered freshwater reservoir during the last glacial period and remained a freshwater reservoir until seawater started encroaching the region at ~8.5 ka. The Ramasetu region was a potential habitat zone for foragers, with fresh and saline water ecosystems available at opposite banks. During the Microlithic and terminal Pleistocene, Homo sapiens needed to cross high-energy rivers using floaters/rafts in wet seasons of MIS 2 and 3. At the same time, they used a direct walkable land link in the extreme dry season of MIS 2. During the early to mid-Holocene, foragers required floaters/rafts or artificial structures (such as bandh/bridge) to cross shallow, low-energy estuarine patches of the Ramasetu. The Palk Strait region was not crossable without using boats/ships in the last ~7 ka except during minor sea-level falls.