Holocene and last interglacial relative sea level changes in Sri Lanka based on geological indicators

Earth’s climate oscillations between interglacial and glacial periods have driven significant sea level changes. Sri Lanka, located in the Indian Ocean, provides an ideal natural setting for studying paleo sea level changes. This study compiles 92 Holocene sea level records and identifies last interglacial stratigraphic evidence from Point Kudrimalai to reconstruct paleo sea level fluctuations in Sri Lanka. In addition, this study evaluates underutilized sea level indicators such as beachrock, coastal barrier sands, and mangrove swamps to address methodological challenges in reconstructing past sea levels. Results show that diverse sea level indicators, including beachrock, coastal barrier sands, raised marine deposits, and marine shell beds, primarily reflect Holocene sea level changes and their geological impacts. Using standardized sea level indicators such as coral and marine shell beds, this study reveals Holocene sea levels approximately 1.0–2.0 m above present between 6000 and 2000 cal BP. The 6–9 m elevation associated with Point Kudrimalai can possibly be correlated with regional Pleistocene sea level highstands. In contrast, the Palk Strait land bridge can be identified as a potential paleogeographic connection during periods of substantially lower sea level. Accordingly, these findings elucidate that the impact of sea level changes in Sri Lanka has likely influenced coastal geomorphology. Therefore, this reconstruction enhances understanding of regional sea level variability and its role in shaping coastal landscapes in the Indian Ocean.