Holocene relative sea-level history of the Gulf of Khambhat, Western India: Revisiting regional records with standardized SLIP protocols

Abstract

The Mid-to-Late Holocene was a period of significant climatic and sea-level fluctuations, particularly pronounced in dynamic coastal systems. In gulf environments, relative sea level changes are influenced by complex, region-specific processes, necessitating localized studies. In this study, we synthesize relative sea-level data from five coastal sites within the Gulf of Khambhat, western India, to reconstruct spatially resolved relative sea level histories using standardized sea-level index points. While only two sites (Lothal and Vadgam) fulfil all sea-level index points' criteria, Saltanpur and Diu Island provide limiting or tectonically influenced indicators. Our results indicate a mid-Holocene relative sea-level high stand ranging from ∼ +1.2 m in the north (Lothal) to ∼ +2.0 m in the south (Diu, uncorrected for tectonic uplift). The observed gradient likely reflects a combination of estuarine infilling, differential sedimentation, tidal range amplification, and localized tectonic uplift. When considered alongside archaeological evidence, these relative sea-level fluctuations may have influenced the navigability and habitability of key Harappan settlements. This study underscores the importance of standardized sea-level index point's methodologies and region-specific reconstructions for understanding Holocene human-environment interactions along macrotidal coastlines.