MORPHOLOGY OF THE VOLCANIC ASH FROM THE KUKADI RIVER SECTION, PUNE DISTRICT, MAHARASHTRA

An ash bed varying in thickness from 20 cm to 2 m occurs within the lo wer part of 10 m thick yellowish-brown clay and calcareous silt unit t hat contains occasional lenses of calcrete, gravels and channel lag gr avels both at the base and top of the sequence. The volcanic ash has y ielded a K/Ar age of 1.4 Ma. The volcanic ash is highly siliceous in c omposition with SiO2 content varying between 72 to 78%. It is dominant ly constituted of silt sized angular glass shards, and pumice fragment s with sharp edges. Petrography, SEM and chemical composition of the g lass shards helps in relating the ash morphology to magma composition and the type of eruption. On the basis of petrographic and morphologic al characters displayed by the volcanic ash, the formation of the glas s shards is attributed to magmatic processes.