Astronomy and Astrophysics – Astronomy
Scientific paper
Apr 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003eaeja....12799l&link_type=abstract
EGS - AGU - EUG Joint Assembly, Abstracts from the meeting held in Nice, France, 6 - 11 April 2003, abstract #12799
Astronomy and Astrophysics
Astronomy
Scientific paper
Correlations between tephra layers interbedded within deep-sea cores and radiometrically dated volcanic eruptions provide an independent means of verifying dating techniques developed for sediment cores. Alternatively, the chronostratigraphic framework developed from marine sediments can be used to calibrate ages of land-base eruptions, if geochemical correlations can be established. In this study, we examined three deep-sea cores along an east-west transection across the South China Sea, with a distance of ~1800 to 2500 km away from the Toba caldera. The occurrence of the Oldest Toba Tuff was recognized on the basis of its geochemical characteristics, such as a high-silicate, high-potassium content and a distinct strontium isotope composition. The correlative tephra layer occurs slightly above the Australasian microtektite layer and below the Brunhes/Matuyama boundary, which in constitute three time-parallel markers for correlation and dating of Quaternary stratigraphic records. Against the astronomically tuned oxygen isotope chronostratigraphy, the rhyolitic ignimbrite erupted during the transition from marine isotope stage 20 (glacial) to stage 19 (interglacial) with an estimated age of 788 ka. The refined age is in good agreement with the radiometric age of 800+20 ka for Layer D of ODP Site 758 (Hall and Farrell, 1995), but significantly younger than the commonly referred age of 840+30 ka (Diehl et al., 1987). The mid-Pleistocene eruption expelled at least 800-1000 km3 dense-rock-equivalent of rhyolitic magma taking into account the widespread ashfall deposits in the Indian Ocean and the South China Sea basins. In spite of its exceptional magnitude, the timing of the first Toba super-eruption disputes a possible causal linkage between a major volcanic eruption and a long-term global climatic deterioration.
Chen Chian-Chou
Iizuka Yoshizou
Lee Minchul
Wei Kun
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