Pleistocene climate and sea-levels: A case study of the microfacies characteristics of carbonate aeolianites (Miliolitic limestone) of Gujarat coast, India

Abstract

Carbonate Aeolianites, a common and conspicuous facies of the Pleistocene and Holocene, provide a wealth of information on fluctuating Quaternary Climates and sea-level changes. The Indian subcontinent having a vast coastline with a varied Quaternary history, exposes along the Gujarat coast, some of the excellent outcrops of Quaternary carbonate rocks, popularly known as "Miliolitic Limestone" of Middle-Late Pleistocene Age. These carbonate deposits with varied field characteristics and textural parameters have been studied in the past to establish the fluctuations of Pleistocene climate and sea-levels. The microfacies and diagenetic character of the Pleistocene carbonate accumulations of Gujarat Coast, Western India are documented in the present paper in order to understand the palaeoclimatology and palaeoenvironmental aspects. The porous, fine-medium grained, miliolitic limestone display large-scale cross-stratification with high angle fore sets dipping chiefly to landward. The benthonic foraminifera-dominated limestone, a pelletal packstone-srainstone, is charactcrized by early stage cement and other diagenetic fabrics characteristic of vadose zone involving dissolution, cementation, neomorphism and micritization. Critical evaluation of the field data, compositional and diagenetic characteristics points to a Middle Pleistocene high sea (+25 m asl) which subsequently regressed to a low level (-100 m bsl) at the close of Pleistocene manifest by the reworking and sub-aerial exposure of the carbonates and subsequent action of meteoric diagenetic processes.