We have identified an ash layer in association with Australasian microtektites of approximately 0.77 Ma old in two sediment cores which are approximately 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 approximately 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 ( approximately 3.6 X 10 (super 7) km (super 2) ), an ash volume of at least approximately 1800km (super 3) , a total OTT volume of 2300 km (super 3) , and classification of the OTT eruption as a super-eruption. Copyright 2010 Indian Academy of Sciences