Preliminary Results of Some Gravity Surveys, in Singhbhum Area, Orissa

The regional gravity survey in the area bounded by Lat. 21°N to 23°N and Long. 85°E to 87°E has brought out a broad gravity' low' over the granite batholith south of the Singhbhum thrust zone. The amplitude of gravity' low' is more in the southern portion (about 30 mgal near Keonjhargarh) than that in the northern portion of the granite batholith (about 20 mgal near Hatgamaria). This gravity 'low' in general suggests that the granite body may continue to a considerable depth.

A broad gravity 'high' has also been observed east of Singhbhum granite where one or two outcrops of basic rocks are observed. The areal distribution of this' high' would seem to suggest the existence of a substantial amount of basic rocks in this area which may represent the Simlipal and the Dhanjori basins filled with high density material as suggested by Iyengar and Alwar.

This correlation of gravity to surface geology can be advantageously used as an aid to structural mapping and in getting the third dimensional configuration of the major rock types.