New occurrence of Youngest Toba Tuff in abyssal sediments of the Central Indian Basin

Volcanic glass and pumice found in siliceous abyssal sediments of the Centr al Indian Basin, south of the Equator, have previously been assigned variou s origins including intra-basin volcanism, Indonesian are, and Krakatau. Rh yolitic glass shards dispersed in sediments from 8 cores that we have exami ned are compositionally identical to those of fallout deposits of the Young est Toba Tuff erupted at 74 ka from northern Sumatra. The correlation exten ds the distribution of coarse (>63 IJ-m) glass shards some 1500 km south of the previously known fallout zone, and into the Southern Hemisphere (reach ing latitudes of ca. 14 degrees S). This provides evidence for bi-hemispher ic dispersal of the ash cloud and supports global dispersal of gas and aero sols from the eruption. Such dispersal could have facilitated the global im pact of the eruption. (C) 1999 Elsevier Science B.V. All rights reserved.