Grain Size and Petrography of Mesozoic Rocks of Saurashtra Basin, Gujarat, Western India

A provenance study was conducted on the Mesozoic rocks of Saurashtra basin, Gujarat, in which grain size, mineralogy and petrographical features of sandstones were integrated to arrive at an consistent interpretation.

Textural parameters suggest progressive variation in that mean grain size increases from Than (0. t 98 - 0.117 mm), Surajdeval (0.257 -0.213 mm), through Ranipat (0.5 -0.378 mm), to Wadhwan (0.716 - 0.469 mm). The bulk of the sandstones demonstrate positive (+) skewness in Than and Surajdeval implying that sandstones include greater admixture of fine sediments, as aganist those of Rani pat and Wadhwan which show excess of coarse admixture. By and large, the Dhrangadhra sandstone is moderately to well sorted (σ I=0.52 - 0.84 φ).

Petrographically, three types of sandstones constitute the Dhrangadhra group of formations, namely, quartzarenite, subarkose and sublitharenite, consisting of quartz, feldspar, lithic-fragments, and mica in order of abundance. Groundmass material consists of cementing material and matrix. Heavy minerals show a preponderance of granet, zircon, tourmaline, staurolite, rutile and epidote. The study reveals a mixed provenance, comprising of acid igneous, metasedimentary rocks of the Aravalli highlands outcropping in the northeastern part of the study area.