Late Holocene (0–6 ka) sea-level changes in the Makassar Strait, Indonesia

Maren Bender,Alessio Rovere,Tilo Schöne,Thomas Mann,Dominik Kneer,Jamaluddin Jompa,Paolo Stocchi,Julia Illigner

doi:10.5194/cp-16-1187-2020

Abstract

Abstract. The Spermonde Archipelago, off the coast of southwest Sulawesi, consists of more than 100 small islands and hundreds of shallow-water reef areas. Most of the islands are bordered by coral reefs that grew in the past in response to paleo relative sea-level changes. Remnants of these reefs are preserved today in the form of fossil microatolls. In this study, we report the elevation, age, and paleo relative sea-level estimates derived from fossil microatolls surveyed in five islands of the Spermonde Archipelago. We describe 24 new sea-level index points, and we compare our dataset with both previously published proxies and with relative sea-level predictions from a set of 54 glacial isostatic adjustment (GIA) models, using different assumptions on both ice melting histories and mantle structure and viscosity. We use our new data and models to discuss Late Holocene (0–6 ka) relative sea-level changes in our study area and their implications in terms of modern relative sea-level estimates in the broader South and Southeast Asia region.

Highlights

After the Last Glacial Maximum, sea level rose as a result of increasing temperatures and ice loss in polar regions
In the most standard definition, microatolls typically form at mean lower low water (MLLW), but their living range can span from mean low water (MLW) down to the lowest astronomical tide (LAT) (Mann et al, 2019a)
Our dataset consists of a total of 25 fossil microatolls (FMAs) surveyed in five islands of the Spermonde Archipelago (Table 2; see the PANGAEA dataset associated with this paper)

Summary

Introduction

After the Last Glacial Maximum, sea level rose as a result of increasing temperatures and ice loss in polar regions. It has long been shown that the higher-than-present relative sea level (RSL) in the Middle Holocene (e.g., Grossman et al, 1998; Mann et al, 2016) is not eustatic in origin but was caused by the combined effects of glacial isostatic adjustment (GIA) (Milne and Mitrovica, 2008), which includes ocean siphoning (Milne and Mitrovica, 2008; Mitrovica and Milne, 2002; Mitrovica and Peltier, 1991) and redistribution of water masses due to changes in gravitational attraction and Earth rotation following ice mass loss (Kopp et al, 2015). Combining the use of precisely measured and dated RSL indicators with GIA models in areas where the highstand occurs, it is possible to improve our knowledge on long-term rates of land-level changes, which need to be con-

Methods

Results

Discussion

Conclusion