Cretaceous Sedimentation in the Sub-Surface of Krishna-Godavari Basin

The NE-SW trending Krishna-Godavari Basin is located at right angles to NW-SE trending Pranhita-Godavari graben ? towards the basin margin. From subsurface exploratory data obtained, it is inferred that NW-SE trending Gondwana graben is .extending underneath Krishna-Godavari Basin. In subsurface, the sedimentary sequence occurring in between the basalt and the ' Red Bed ' is demarcated as the Cretaceous sequence. This sequence is further divisible into three litho-units as equivalents to Gollapalli sandstone, Raghavapuram shale and Tirupati sandstone.

The depositional environment for Gollapalli sandstone is interpreted to be mainly fluvial towards NW of Tanuku horst and paralic towards SE of the horst. The Raghavapuram shales were deposited under marine conditions. The upper part of Tirupati sandstone is of fluvial nature around Kommugudem area and changes gradually to paralic and to marine towards the southeastern part of the Basin.