Vindhyan and Deccan Trap

The eastern and southern extremities of the Aravalli ranges in Rajasthan mark the beginning of two different geological formations. The Vindhyan hill system and the Deccan trap begin here. The Vindhyan system lies above the older formations and constitutes an unmetamorphosed column of calcareous, arenaceous and argillaceous sediments which cover a vast area, its varying depth peaking at a maximum thickness of 4,300 m. The Vindhyas in the state are part of the Great Vindhyan Basin, extending from Rohtas in Bihar to Chittorgarh in Rajasthan. The contact between the pre-Aravalli and Vindhya is marked y a regional fault, the great boundary fault, which masses the Aravallis against the lower Bhander quartzites of the Vindhyan group. This great boundary fault passes through the Ranthambhore national park in Sawai Madhopur.

Vindhyan sandstone is, by far, the most common rock found in the state, with the exception of the lower Bhander stage which, for the greater part, is calcareous. The sandstone is of a uniform fine grain, preserving the uniformity of texture and composition unchanged over long stretches. The Kaimur as well as Bhander sandstone is a fine textured, soft, easily workable stone with a deep red tint. It passes occasionally into softer shades in Karauli. These stones have a great market for building and other architectural purposes.

The topography is varied. Hill slopes change from very gentle to steep, ending in escarpments forming impregnable barriers. Extensive plateaus, locally called dangs, have been formed y the flat-topped hills of the Vindhyas. With its rich grasses and sparse tree growth, the dangs are a good pasture-land for herbivorous wild animals and domestic cattle. The Vindhyan forests of dhok and other species associated with it provide in excellent habitat for the tiger and its prey species.

The Deccan trap formation occurs in the state’s southern extremities of the Vindhyan an Aravalli ranges. Towards the end of the Mesozoic era, there were extensive eruptions an flows of lava in the peninsula which occlusive lava flows were separated by sedimentary beds. The thickness of the column of lava flows and sedimentary beds varied from place to place. The lava flows gave rise to the flat-topped hills and plateaus with their step-like terraces. The formation as a whole is called the Deccan trap.