An inflection in the rate of early mid-Holocene eustatic sea-level rise: A new sea-level curve from Singapore

Abstract

This study presents a sea-level curve from w9500 to w6500 cal BP for the farfield location of Singapore, on the Sunda Shelf in southeast Asia. The curve is based on more than 50 radiocarbon dates from elevations of þ1.43 m to À15.09 m representing sea-level index points in intertidal mangrove and shallow marine sediments deposited by sea-level rise accompanying deglaciation. The results indicate that mean sea level rose rapidly from around À17 m at 9500 cal BP to around À3 m by 8000 cal BP. After this time, the data suggest (but do not unequivocally prove) that the rate of sea-rise slowed for a period of 300e500 years centred on w7700 cal BP, shortly after the cessation of meltwater input to the oceans from the northern hemisphere. Renewed sea-level rise amounting to 3e5 m began around 7400 cal BP and was complete by 7000 cal BP. The existence of an inflection in the rate of sea-level rise, with a slow-down centred on w7700 cal BP, is broadly consistent with other available sea-level curves over this interval and is supported by evidence of stable shorelines and delta initiation elsewhere at this time, as well as evidence of comparatively rapid retreat of the West Antarctic ice sheet beginning around 7500 cal BP. 'Stepped' sea-level rise occurring shortly after 7500 cal BP and also earlier during deglaciation may have served to focus significant post-glacial episodes of human maritime/coastal dispersal, into comparatively narrow time intervals.

Évolution des paléoenvironnements dans le Pacifique lors de la dernière déglaciation : exemples en Nouvelle-Calédonie et au Vanuatu

“…Les variations en apports d'éléments nutritifs observées pendant cette période auraient égale-ment influé fortement sur la croissance des formations récifales (Montaggioni et al, 2006), contribuant au retard de l'établissement des récifs modernes en Nouvelle-Calédonie. Vers cette même période de l'Holocène moyen, on observe aussi une inflexion dans la remontée du niveau marin qui a été observée en Australie (Larcombe et al, 1995) et à Singapour (Bird et al, 2007) qui aurait pu favoriser une croissance de rattrapage pour les récifs modernes. L'installation et le développement des récifs modernes tels qu'ils sont observés en Nouvelle-Calédonie répondent donc à une double influence, locale (aptitude des substrats, sst) et globale (upwellings et variations du niveau marin).…”

“…Parmi ces variations climatiques, celles qui ont eu lieu à 14 100 et 11 300 ans sont attribuées à une accé-lération de débâcles glaciaires (Melt Water Pulse 1A et 1B, respectivement MWP-1A et MWP-1B, Fairbanks, 1989 ;Bard et al, 1996). À l'inverse un ralentissement de la remontée du niveau de la mer a été mis en évidence aux alentours de 8 200 ans (Bird et al, 2007). La croissance réci-fale connaît un développement optimum entre les phases de remontée rapide du niveau marin, au cours desquelles et selon les régions, s'observe une recolonisation après les ennoiements dus à ces accélérations.…”

Holocene Relative Sea-Level Changes from Near-, Intermediate-, and Far-Field Locations

“…Holocene studies from the Malay-Thai peninsula suggest a RSL highstand of up to 5 m between 6 and 4 ka, which may have exhibited an oscillatory subsequent fall [153,160,164,[169][170][171][172][173]. The highstand varies in magnitude by 3 to 4 m due to spatial variability from hydro-isostasy [167 ].…”

Response of rice cultivation to fluctuating sea level during the Mid-Holocene

“…Significant sea-level rise happened in the early Holocene, although there are many opinions on the magnitude, process, and rate of sea-level rise [1]. Relatively rapid sea-level rise continued until 7.5 ka BP, after which there was a general falling trend in the rate of sea-level change; however, fluctuations continued [2]. Most coastal areas in China have records of transgressions caused by sea-level rise in the Holocene.…”