Evidence for upper mantle intrusion in the west African coastal sedimentary basins from gravity data: the case of the southern part of the Douala basin, Cameroon

Abstract

The Bouguer anomaly map of the region between latitudes 30N and 3045’N and longitudes 9030’E and 10010’E and which forms the southern part of the Douala Basin, shows ring-like positive contour lines. The Bouguer gravity profiles obtained across the gravity anomaly contour lines in the region have been interpreted using 2D1/2 gravity modelling. The results reveal that in the southern part of the Douala Sedimentary Basin, two major structures exist: a half-dome of mantle material explained by isostatic compensation and a pillar of high density rocks probably representing an upper mantle intrusion down to a depth of about 14 km. The similarities of these results with those obtained in the coastal sedimentary basin of Mauritania-Senegal suggest a more extensive movement that would have affected the whole of West African coast.

KEYWORDS: Bouguer anomaly, dome, graben.