Correlation of the oldest Toba Tuff to sediments in the central Indian Ocean Basin |
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| Authors: | J N Pattan M Shyam Prasad E V S S K Babu |
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| Institution: | (1) Institute of Biogeochemistry and Marine Chemistry, University of Hamburg, Bundesstrasse 55, 20146 Hamburg, Germany;(2) Geological-Paleontological Institute, University of Basel, Bernoullistrasse 32, 4056 Basel, Switzerland;(3) National Institute of Geological Sciences, University of the Philippines, Diliman, Quezon City 1101, Philippines;(4) Philippine Institute of Volcanology and Seismology, C.P. Garcia Avenue, Diliman, Quezon City 1101, Philippines |
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| Abstract: | We have identified an ash layer in association with Australasian microtektites of ∼0.77 Ma old in two sediment cores which
are ∼450 km apart in the central Indian Ocean Basin (CIOB). Morphology and chemical composition of glass shards and associated
microtektites have been used to trace their provenance. In ODP site 758 from Ninetyeast Ridge, ash layer-D (13 cm thick, 0.73–0.75
Ma) and layer-E (5 cm thick, 0.77–0.78 Ma) were previously correlated to the oldest Toba Tuff (OTT) eruptions of the Toba
caldera, Sumatra. In this investigation, we found tephra ∼3100 km to the southwest of Toba caldera that is chemically identical
to layer D of ODP site 758 and ash in the South China Sea correlated to the OTT. Layer E is not present in the CIOB or other
ocean basins. The occurrence of tephra correlating to layer D suggests a widespread distribution of OTT tephra (∼3.6 × 107 km2), an ash volume of at least ∼1800 km3, a total OTT volume of 2300 km3, and classification of the OTT eruption as a super-eruption. |
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