Memoirs of the Geological Survey of India Mineral Resources of Madras

They comprise the Ghats of the Northern Circars composed of charnockites and khondalities the quartzite and shale ridges of the border of Nellore and Cuddapah districts (forming the Velikodas Nallamalais and Palkondas) and the hills of charnockites and Dharwarian rocks in Arcot and Salem (the J avadi Hills Kalrayan Hills Shevaroys etc.) continuing into the southern border of the Mysore p [...] The total rainfall in the region to the west of the crest of the Western Ghats is of the order of 100 inches per annum. [...] There are three main peneplains in this part of India the lowest being the coastal plain the middle one comprising the Mysore plateau and the lower ridges and hills and the upper one the Nilgiri uplands. [...] Only the Ariyalur Stage is developed in the Vriddhachalam and the Pondicherry areas the three areas being separated from each other by the alluvia of the Vellar and the Ponnaiyar. [...] Special mention may be made of the slates from the ' Cumbum Slates' worked near Markapur the Narji limestones and marbles worked in the Palnad area of Guntur and the Cuddapah slabs of the Jammalamadugu and Kundair formations in the Cuddapah and Kurnool districts.