Relative sea-level highstands in Thailand since the Mid-Holocene based on 14C rock oyster chronology

• Published in: Palaeogeography, palaeoclimatology, palaeoecology Vol. 517; pp. 30 - 38
• Main Authors: Oliver, G.J.H., Terry, J.P.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2019
• Subjects: Fixed biological indicators; Sea level change; Tidal notches; Sea level change; Tidal notches; Fixed biological indicators
• ISSN: 0031-0182; 1872-616X
• DOI: 10.1016/j.palaeo.2018.12.005

The relative sea-level highstands in Thailand from the Mid-Holocene to the present day have been studied in horizontal tidal erosion notches and inside a sea cave in limestone and marble coastal cliffs through 14C dating of rock oysters. Rock oyster ages progressively increase with elevation up from a ~1 m wide living oyster band at the present day sea level and up into the roof of the notch. The oldest age obtained is 6513–6390 cal yr B·P. (Mid-Holocene) for a shell at an elevation of 2.5 ± 0.1 m above present day MSL. However, comparison of the results from different sites shows that oysters of the same age occur at different elevations due to different environmental conditions: ~6000 cal yr B.P. old oysters can be found from between 3.8 ± 0.1 m to 2.5 ± 0.1 m above present day mean sea level. A conservative view of these results from Thailand is that relative sea levels were 2.5 ± 0.5 m above the present sea level during the temperature maximum of the Holocene Climactic Optimum between 7000 and 6000 cal yr B.P. Since then, relative sea levels fell until the onset of the Industrial Revolution. •This paper uses dead oyster shells in tidal notches to 14C date the mid Holocene sea-level highstand in Thailand.•The distribution of oyster shells at any one site depends on the local environment.•This introduces an error in sea-level estimation of ±0.5 m.•The relative sea level was 2.5 ± 0.5 m above the present level during the mid Holocene between 7000 and 6000 years ago.