Gravity Anomalies and the Godavari Rift, India

Abstract

A Bouguer anomaly map of the Godavari valley region extending from the deltas of the Krishna and Godavari rivers has been prepared by using data of the Survey of India and National Geophysical Research Institute. A gravity “low” of the order of 50 milligal is associated with the Godavari valley. A comparison of this map with the geologic map of India and the paleogeographic maps of the Gondwana periods by Fox (1931) and Ahmad (1961) indicates the Godavari structure continues northwestward at least up to 23° N. Godavari valley appears to be a rift, according to the definition of a rift valley given by Girdler (1963). Its average width is 50 km and its lateral extent, as indicated by gravity and paleogeographic data, may be of the order of 800 km. The valley floor may lie at depths ranging from 3 to 4 km. The gravimetric and geologic data do not indicate extension of the Godavari valley structure into the sea. However, it appears to have its counterpart in the basins on the western and northwestern coasts of Australia. It is suggested that the Godavari rift developed along a zone of weakness inherited from the Archean orogenies. It appears that after the Eparchean interval, but prior to the deposition of the Cuddapahs, tensional forces must have developed that caused formation of the graben, according to a mechanism proposed by Vening-Meinesz and Heiskanen (1958).