Mineralogy of Saurashtra Miliolites

The results of CaCO₃, carbonate minerals and quartz measurements on 114 miliolites (some of which are dated) and of sedimentatogical and clay mineral studies on select (10-20) samples are reported and discussed.

The miliolite deposits are predominantIy calcite (CaCO₃ range = 50.2 to 100 %, mean 86.8 %) with aragonite and quartz as minor components. None of the measured parameters show any trend/pattern between coast and inland which, coupled with field observations indicate that long distance (< 100 Km) eolian transport was unlikely.

Despite the fact that miliolites rest on Deccan trap basalts and several local and Narbada and Tapti river sediments as well as the near coastal sediments of Saurashtra are enriched in clay mineral smectite, the miliolite clays show the dominance of illite which is principally generated by weathering of granites and brought by the Indus river. This observation implies that the processes responsible far bringing Indus clays to Saurashtra region when the miliolites were formed (60 Kyr - 200Kyr) are not operative in recent times.