Geomorphological studies of the Sedimentary Cuddapah Basin, Andhra Pradesh, South India

Abstract

: The crescent shaped Cuddapah basin located mainly in the southern part of Andhra Pradesh and a little in the Telangana State is one of the Purana basins. Extensive work was carried out on the stratigraphy of the basin, but there is very little reference (Vaidynathan,1964) on the geomorphology of the basin. Hence, an attempt is made to present the geomorphology of the unique basin. The Major Geomorphic units correspond to geological units. The important Physiographic units of the Cuddapah basin are Palakonda hill range, Seshachalam hill range, Gandikota hill range, Velikonda hill range, Nagari hills, Pullampet valley and Kundair valley. In the Cuddapah Basin there are two major river systems namely, the Penna river system and the Krishna river system. The Penna river system has more network of rivers than the river system of Krishna. Further, the Pennar river system drains the southern half of the basin, whereas the river Krishna drains mainly the northern most part of the basin. There is no major river in between these two. The rivers of Pennar systems have their origin from Mysore upland area, whereas the rivers of Krishna systems have their origin from the northern Karnataka area. Most of the rivers are superposed. They are mainly controlled by the structural features / elements. be divided into structural landforms, fluvial landforms and denudational landforms. Structural landforms: Cuesta, hogback, structural ridge, structural plateaus, mesa, domes. Fluvial land forms: Water channel with flood plain, alluvial fans, piedmont zone, valley fill and solution forms. There is well developed karst topography in the basin in the limestone of the Kurnool Group. In addition to all these, the famous Natural Arch is also an eye catching geomorphic feature of the basin. The critical study of cross sections along certain latitudes and along the hill ranges revealed a number of erosional surfaces in and around Cuddapah basin. These surfaces are correlated with the surfaces noticed in the Karnataka and Tamil Nadu. They are, i. Annamalai Surface - at an altitude of over 8000 ’ (2424 m), ii. Ootacamund Surface – at 6500’-7500 ’ (1969-2272 m) on the west and at 3500’ (1060m) on the east as noticed in Tirumala hills, iii. Karnataka Surface 2700 ’ -3000 ’ (Vaidynathan, 1964). 2700-3300 (Subramanian, 1973) 2400-3000 (Radhakrishna, 1976), iv. Hyderabad Surface – at 1600’ – 2000’v. Coastal Surface – well developed east of the basin.vi. Fossil surface: The unconformity between the sediments of the Cuddapah basin and the granitic basement is similar to ‘Fossil Surface’.