Raw gravity data acquired using a Lacoste and Romberg (model G446) gravimeter and its accessories have been converted to a digital data
set and were contoured to produce the first Bouguer gravity anomaly map of Calabar Flank. The data were corrected for drift and elevation (Bouguer and free air). The average crustal density of 2.67g/cm3 was used to compute the Bouguer correction. The effect of the curvature of the earth was taken into consideration. To account for tidal effect, an observational time window for forty-eight hours was determined prior to the actual field survey. Humidity/temperature correction was made to remove effects caused by humidity/temperature variations on raw data. The data was latitude-corrected based on the 1967 Geodetic Reference System (GRS67). This invariably gave the theoretical gravity. A comprehensive computer program for processing raw gravity data was used to compute the Bouguer and free air anomalies and were converted from their geodetic coordinates to x-y coordinates. The data were then transformed to an equally spaced grid (1km). The Bouguer and free air anomaly maps were produced from this grid using a Surfer Plot program. The results from these analyses showed a close relationship between the Bouguer and free air anomaly data; which is compatible with mid-continental results. Calabar Flank is largely not in isostatic equilibrium judging from the dominance of shortwavelength free-air anomaly patterns. The circular, elliptical contours in the Bouguer and free air anomaly maps are lineaments with distinctive trends. These trends indicate structural features that pre-date exposed geology and that have probably controlled the tectonic expressions of the geological province
