Mid to Late-Holocene relative sea-level fluctuations and palaeoenvironment: Evidences from the southern Saurashtra coast, western India

Around 2 m thick relict mudflat, stabilized coastal dune and marine notches are used to estimate the relative sea level (RSL) changes during the mid-Holocene along the part of southern Saurashtra coast. The study identifies two events of high RSL which are dated to 7.3 cal yr BP to 5.1 cal yr BP (Mid-Holocene) and -1 ka BP (LateHolocene). Based on the geochemical proxies, the Mid-Holocene high RSL is ascribed to the combined contribution of global ice melt and the strengthened Indian Summer Monsoon (ISM), whereas, the Late-Holocene high RSL is attributed to the Medieval Climate Anomaly. A decline in the ISM is observed at -4.2 ka which also corresponds with the declining trend in the RSL. However, after 4 ka, a sustained ISM is inferred which continued till 1 ka. The uplift estimated based on the tectonic overprinting of the raised intertidal platforms and marine notches shows -1.5-2 m uplift after the Mid-Holocene. This implies that the net RSL component during the Mid to Late-Holocene was marginally high (above the present high-tide mark). Further, the notch morphology and empirically driven erosion rate estimates indicate that the coastal uplifts occurred at <= 4 ka and was probably responsible for the present-day coastal configuration.

Automated summary

The study on the relative sea level changes during the mid-Holocene along the southern Saurashtra coast reveals two high RSL events during the Mid-Holocene and Late-Holocene, attributed to global ice melt, strengthened Indian Summer Monsoon, and the Medieval Climate Anomaly. A decline in the Indian Summer Monsoon is observed around -4.2 ka, corresponding to a declining trend in the RSL, while uplifts around <= 4 ka likely contributed to the present-day coastal configuration.