G. Lakshminarayana, SEDIMENTOLOGICAL EVIDENCE FOR CRETACEOUS REACTIVATION OF THE EASTERN MARGIN OF THE CUDDAPAH BASIN, Journal of the Geological Society of India, 49(2), 1997, pp. 159-168
The east coast Cretaceous Sedimentary basins namely the Krishna-Godava
ri Basin (K-G Basin) in north and the Palar Basin in south are located
towards the tapering ends of the crescent shaped 'Cuddapah Basin'. Cr
etaceous stratigraphic succession in ascending order is Raghavapuram a
nd Tirupati formations in the K-G Basin and Sriperambattur and Satyave
du formations in the Palar Basin. The Raghavapuram and Sriperambattur
formations consist of mainly shale and siltstone deposited in prodelta
/shallow marine environments. Sedimentological studies on sandstone an
d conglomerate revealed that in the Tirupati Formation coarse elastic
detritus was derived from the Archaean crystallines and Proterozoic Cu
ddapah and Kurnool Groups of rocks by braided streams flowing towards
east. Alluvial fans and the associated braided streams originated in t
he southern part of the 'Cuddapah Basin' were fed by mainly 'Nagri Qua
rtzite' to deposit the bouldery conglomerate, conglomerate and sandsto
ne sequence of the Satyavedu Formation. The Cretaceous sedimentary out
crops located east of 'Cuddapah Basin' i.e. Guntur, Ongole and Nellore
areas show evidence for deposition in fluvial and fluviomarine settin
gs. The Early Cretaceous tectonic disturbances coinciding with the bre
ak up of India from east Gondwanaland reactivated the eastern margin o
f the 'Cuddapah Basin' thereby enabling it to supply increased amount
of detritus to the coastal sedimentary basins. However, the central pa
rt of the 'Cuddapah Basin' and the adjacent shield area located betwee
n Lat. 14 degrees and 16 degrees acted as a water divide to the Cretac
eous drainage.