Abstract
New data on Holocene sea levels have been obtained in 28 atolls and 10 high islands in the Society, Tuamotu, Gambier and Austral Islands, in an area of the South Pacific as wide as western Europe. Sea-level indicators are often very accurate (±0.1 m) and include exposed corals, abandoned algal ridges and reef frameworks in growth position, emerged tidal notches, and skeletal reef conglomerates in which the position of the former low water level at the time of cementation has been determined by petrological analysis. Over 110 new samples have been dated by radiocarbon. The overall pattern is that of a MSL standstill at +0.8/+1.0 m between 5000 and 1250 yr B.P. A set of radiocarbon dated samples covering the period 4500-1250 yr B.P. almost continuously is evidence that lasting MSL drops could not ever have occurred below +0.7 m throughout this time. The highest sea-level peak (about +1.0 m) seems to have been reached between 2000 and 1500 yr B.P. Since 1500 yr B.P. MSL has been dropping gradually from about +1.0 m to the present position, which has been reached only recently. Some islands show however a slightly different pattern; the Holocene emergence is smaller than average in Moorea and Tahiti and larger in Rurutu, Makatea, Anaa, and possibly Hereheretue. Some data suggest also the possibility of a slight increase in the Holocene emergence towards the south. Possible geodynamic, isostatic, oceanic and climatic causes of the sea-level variations observed are discussed.
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