Mineralogy and Petrography of the Subsurface Alluvium Samples from Mahanagar Borehole, Lucknow (U.P.)

Mineralogical and petrographical studies of the samples from the subsurface alluvium near Lucknow, from a depth of 253 to 485 m, are presented. The sediments are marked by poor sorting, high content of subangular rock fragments and clay matrix. Both plagioclase and alkali felspar are present in the sand as well as silt fractions. Petrographically the sediments are lithic graywackes. Clay minerals present are montmorillonite, kaolinite, and illite. Quartz grain surface textures are dominantly glacial, along with some fluvial features. Heavy mineral assemblage is marked by the dominance of extremely fresh grains of very unstable minerals, e.g. garnet, epidote, hornblende, kyanite, tremolite. Tourmaline, apatite, zircon, and chlorite are also present.

It is suggested that the sediments were deposited by the high-gradient, rapidly flowing rivers coming from the Himalayas. Sediments were supplied from a glacial affected terrain, made up mainly of low to high grade metamorphics, and some granitic rocks. Deposition was rapid in the quickly sinking fluvial basin.