Clay Mineral Distributions in Dated Miliolites of the Late Quaternary from Saurashtra and Kutch, Gujarat

Forty-three dated miliolites (ages ranging from 30-235 kyr) of the late Quaternary period, from Saurashtra and Kutch regions of Gujarat State have been analysed for their detrital contents as well as for the four clay minerals, smectite, illite, kaolinite, and chlorite in the less than 2 micron fraction.

Between 235 kyr and 140 kyr BP. there was less detrital material available in the regions of miliolite formation. Landward and seaward sources, notably from southeast and northwest directions contributed equally efficiently to the clay component of the detritus resulting in illite smectite ratio of 1.0. This situation prevailed during 70-50 kyr BP as well as at around 12 kyr BP except that the total detritus in miliolites increased by a factor of about three, during the two recent periods. However, during 95-115 kyr BP, despite the high detrital content of 24%, the illite/smectite ratio dropped to 0.3 indicating the expected dominance of the local and southeastern sources which are enriched in smectite in their clay fractions.