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AbstractAbstract
[en] Twelve Late Quaternary TIMS U-Th ages are reported here from 10 coral samples collected in situ from five transgressive coral/algal raised reefs (height: max. 113m, min. 8m) and two raised lagoonal deposits (height: max. 18 m, min. 8 m) along and near the west coast of Tanna, which lies in the Median Sedimentary Basin of South Vanuatu, southwest Pacific. These reefs and raised lagoonal deposits represent several age groups: (i) 215ka (marine oxygen-isotope stage 7) penultimate interglacial (highest elevation and oldest); (ii) one lagoonal deposit of ca 127 ka (marine oxygen-isotope stage 5e); (iii) three last interglacial reefs with ages 102, 89 and 81 ka (representing marine oxygen-isotope stages 5c, 5b and 5a, respectively, of the latter part of the last interglacial); (iv) a lagoonal deposit with a 92 ka age (5b); and (v) a Holocene reef (age >5.7-5.0 ka) (lowest elevation and youngest). A ca 4.9 ka regressive reef (at elevation of 1.5 m above sea-level) is consistent with an island-wide 6.5m uplift (probably largely coseismic), and a probable further island-wide uplift-occurred in the late Holocene. The U-series ages taken together with the heights of transgressive reefs show that uplift since 215 ka was, on average, at -0.52 mm/y, although since 5 ka the uplift rate was, on average, ∼1.6 mm/y (the assumption being that a 1.5 m above sea-level reef has a coseismic origin) Elevation of transgressive reefs 5a, 5b and 5c and their ages indicates an island-wide subsidence during the period ?124-89 ka (i.e. Late Quaternary uplift/subsidence was jerky). Late Quaternary uplift/subsidence on the northwest coast of Tanna is considered to be due to irregular thickness of crust being subducted beneath Tanna. Copyright (2003) Geological Society of Australia
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41 refs., 1 tabs., 7 figs.
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Journal Article
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Numerical Data
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ACTINIDE NUCLEI, ACTINIDES, AGE ESTIMATION, ALPHA DECAY RADIOISOTOPES, ANIMALS, CENOZOIC ERA, CNIDARIA, COELENTERATA, DATA, DAYS LIVING RADIOISOTOPES, ELEMENTS, EVEN-EVEN NUCLEI, GEOLOGIC AGES, GEOLOGIC STRUCTURES, HEAVY ION DECAY RADIOISOTOPES, HEAVY NUCLEI, INFORMATION, INTERNAL CONVERSION RADIOISOTOPES, INVERTEBRATES, ISOTOPES, MAGNESIUM 28 DECAY RADIOISOTOPES, METALS, NEON 24 DECAY RADIOISOTOPES, NUCLEI, NUMERICAL DATA, RADIOISOTOPES, SEAS, SPONTANEOUS FISSION RADIOISOTOPES, SURFACE WATERS, THORIUM ISOTOPES, URANIUM ISOTOPES, YEARS LIVING RADIOISOTOPES
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