Depths to density discontinuities beneath the Adamawa Plateau region, Central Africa, from spectral analyses of new and existing gravity data

New gravity data from the Adamawa Uplift region of Cameroon have been integ rated with existing gravity data from central and western Africa to examine variations in crustal structure throughout the region. The new data reveal steep northeast-trending gradients in the Bouguer gravity anomalies that c oincide with the Sanaga Fault Zone and the Foumban Shear Zone, both part of the Central African Shear Zone lying between the Adamawa Plateau and the C ongo Craton. Four major density discontinuities in the lithosphere have bee n determined within the lithosphere beneath the Adamawa Uplift in central C ameroon using spectral analysis of gravity data: (1) 7-13 km; (2) 19-25 km; (3) 30-37 km; and (4) 75-149 km. The deepest density discontinuities deter mined at 75-149 km depth range agree with the presence of an anomalous low velocity upper mantle structure at these depths deduced from earlier telese ismic delay time studies and gravity forward modelling. The 30-37 km depths agree with the Moho depth of 33 km obtained from a seismic refraction expe riment in the region. The intermediate depth of 20 km obtained within regio n D may correspond to shallower Moho depth beneath parts of the Benue and Y ola Rifts where seismic refraction data indicate a crustal thickness of sim ilar to 23 km. The 19-20 km depths and 8-12 km depths estimated in boxes en compassing the Adamawa Plateau and Cameroon Volcanic Line may may correspon d to mid-crustal density contrasts associated with volcanic intrusions, as these depths are less than depths of 25 and 13 km, respectively, in the sta ble Congo Craton to the south. (C) 2000 Elsevier Science Limited. All right s reserved.