The Alwar Group mainly consists of arenaceous and mafic volcanic rocks. These were once sandstones and arenaceous rocks. For the Lower Tal, there are four subdivisions&colon; the Chert, Argillaceous, Arenaceous and Calcareous Units. It is thick and is composed greenish grey to brownish grey arenaceous shale. In geology, Torridonian describes a series of proterozoic arenaceous sedimentary rocks of Precambrian age. Additional fossils include radiolarians, arenaceous foraminifers, and remains of sponges. The plain of Lafonia is constituted by arenaceous sediments of the Lafonia Group. The related adjective is "arenaceous". Arenaceous rocks, calcareous rocks and evaporites are the dominant rock type in the Marwar Basin.