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| Titel |
Reconstruction of Late Holocene sea-level change in French Polynesia, South Pacific, based on coral reef records |
| VerfasserIn |
Nadine Hallmann, Gilbert Camoin, Anton Eisenhauer, Claude Vella |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250074390
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| Zusammenfassung |
| Fossil reefs provide valuable sea-level indicators, which help to improve the understanding of
past sea-level fluctuations and the prediction of future changes. Recent sea-level changes
were reconstructed from emerged reef platforms of two high islands from the Society Islands
(Bora Bora, Moorea) and two atolls from the Tuamotu Archipelago (Rangiroa,
Tikehau), French Polynesia. These mid-ocean islands can be regarded as tectonically
stable for the past few thousand years. Therefore, they are well suited for sea-level
studies because they register Holocene eustatic changes, which are not overprinted
by tectonic changes. Furthermore, the study sites are located distant from former
ice sheets (far field location), which reduces the influence of the glacio-isostatic
rebound.
Several sea-level indicators, such as in situ coral colonies, including coral microatolls
(Porites sp.), bivalves (mainly Tridacna sp.), conglomerates, beachrock, and sediments were
analyzed in order to reconstruct Late Holocene relative sea-level changes. Microatolls are
discoid corals that develop laterally when upward growth is limited by sea-level. Therefore,
they are very accurate recorders of past sea-level. This study provides a detailed sea-level
history for French Polynesia using high-precision U/Th (TIMS) dating and GPS
measurements with a vertical and horizontal precision of 1-3 cm and a few millimetres,
respectively. All samples were analyzed by X-ray diffraction and examined petrographically
to exclude diagenetically altered material.
The Holocene mean sea level in French Polynesia was thought to have been higher than
present (+0.8/+1.0 m) between 5000 and 1250 yr BP, reached a highstand between 2000 and
1500 yr BP and then decreased to the present level (Pirazzoli and Montaggioni, 1988). The
highstand has been reported until 1200 yr BP in the Tuamotu Archipelago (Pirazzoli and
Montaggioni, 1986). However, sea-level indicators analyzed in this study reveal a
highstand of at least 1.5 m above the present sea level. Such high resolution and
high precision sea-level data are essential to refine last deglacial sea-level changes
and to improve models for the prediction of future global and regional sea-level
rise. |
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