The aluminum concentration in the marine sediments has long been considered an indicator of terrigenous abundance. The Al/Ti values (48.5) of the Central Indian Basin subsurface siliceous sediment are up to three times that of Post-Archean Australian Shale (PAAS). The estimation of structurally unsupported Al (Al sub(ex)) from six sediment cores suggests that an average of 40% of total Al is from noncrustal sources. Higher Al/Ti or Al sub(ex) values are often, but not exclusively, associated with abundant volcanic unaltered glass shards. Electron microprobe analysis of 60 of these glass sharde reveals that they are rhyolitic in composition and of Youngest Toba (74 ka) origin from Northern Sumatra. These glass shards have very high Al/Ti ratio of 175 (mean). Al/Ti values are also above the PAAS in sediment where glass shards are absent, which could be due to scavenging of dissolved Al by biogenic components