An Encyclopaedia of Indian Archaeology v2.c34.398

v2.c34.398

The Upper Gondwana rocks in the e. coast are a relic of the great marine transgressions. A few small inliers of these rocks occur among the younger Tertiary and post-Tertiary [9.8] formations. One such transgression is marked by the formation of the Sriperumbudur shale overlain by the Satyavedu sandstone, both of the Upper Gondwana age, and underlain by Archaic gneisses. The Satyavedu sandstone is mainly a deposit of boulder-conglomerate, the binding matter being a ferruginous compound liable to lose its holding capacity under water action. This resulted first in the loosening of the boulders forming talus cones and then a dispersal into boulder slopes by soil creep, the latter being easy because of the clayey composition of the underlying shale. This further resulted in the remnant of the Satyavedu sandstone deposits in the form of some ridge-like hills with its general axis in the n.-e. to s.-w. direction. The ferruginous solution mixed with the clayey mass has passed several times over the different regions of the slope over the thick boulder deposit. This slope culminates at the first peneplain, now confirmed as a marine terrace, where the top clayey mass of the shale has been so impregnated with ferruginous solution that it has assumed the form of and has even been described as a laterite [9.6]. Over this there is the first spread of loose boulders which contain Middle Acheulian tools [4.2]. The boulder deposit, often approximating 15 m in thickness constituting the slope, contains throughout tools from the Middle Acheulian to Middle Palaeolithic [4.3], the ones farthest from the talus cone being the earliest and so on thereby maintaining a horizontal stratigraphy.