Deep structure, origin and evolution of the Guinean marginal plateau according to the results of three-dimensional gravity modelling
© Kozlenko M.V., Kozlenko Yu.V.
On the base of conducted three-dimensional gravity modeling parameters of deep structure of the earth's crust and the upper mantle of the Guinean marginal plateau have ben revealed, according to which tectonic elements and special features of formation of this structure were found. Together with submeridional precontinental foredeeps elements of sublatitudinal strike have been distinguished, similar by their character to transform faults of Middle Atlantic ridge. The conclusion has been made that the plateau is located at the joint of two margins - classical passive in west-eastern direction and the passive shift one in north-southern direction. In addition to orthogonal system the diagonal one takes part in formation of structural elements, in particular, north-western border of the block of consolidated basement, known as the Kasine protrusion, is being formed by extension of fault zone Bissau-Kidira to water area. It has been found that in this region specific crust has been produced, which is heterogenous along the lateral and represented by continental, transitional and oceanic types. The southern and western parts of the plateau are underlied by oceanic crust. The northern and the eastern ones - by transitional, formed at the expense of thinning and consolidation of continental crust during the process of fragmentation and basification of the basement under conditions of endogenous regime of formation the rift of the Atlantic ocean. Special features of contemporary morphostructure, which discriminate the plateau from the other areas of the continantal margin of the West Africa, are distinguished by the fact that sublatitudinal ridges of the Guinean fault zone were the barrier preventing ablation of sediments from the African continent to the south in direction of Sierra Leone depression but allowed unlimited extension of the sediments westward.