Tamil Nadu Uplands cover about 60,000 sq. km of area between South Sahyadri and Tamil Nadu coastal plains. The major portion of the region is covered widi gneissic formation. The chamockites are found in die Javadis, and Shevaroys.
The Archaean gneisses and schists have been intruded by dykes of the Cuddapah system owing to volcanic activity. The alluvial formations are noticed in the eastern part of the upland region along the river courses.
Physiographically the Tamil Nadu Uplands are divided into two sub-units: (i) The Tamil Nadu Hills, and (ii) The Coimbatore-Madurai Uplands. The former constitutes small but bold hill masses. Notable among these are the Javadis, ‘he Shevaroys, the Kalrayans, and the Pachamalais. Hie Shevaroys spread over an area of 250 sq. km, rising to 1525- 1647 m in elevation. Javadis is limited to an altitude of 1098-1160 m. The Coimbatore upland rises gradually from 122-183 m along the Kaveri to 366-457 m in the west. It has a crescentic shape widi gradual
slope towards the interior. Here the insignificant watershed between the Noyil river in the north and the Amravati in the south is remarkable. In between Coimba’ore and the Anaimalais, there is the broad Palghat gap cut across the Western Ghats by a river of former “eological epoch (Aycngar, 1930, p. 54).
The Madurai Upland extends almost upto the foot of the Sahyadris with minor elevations here and there as in the Valanad Hills. The Vaigai and Tambraparni basins arc important in this region. The general slope of this area is towards the east. The Kavcri valley lies to the north-cast and east of Kongundu upland (300 m) is densely populated.