Characterisation of tectonic lineaments in the Central Equatorial Atlantic region of Africa using Bouguer anomaly gravity data

Abstract

3-D standard Euler deconvolution analysis was carried out on Bouguer anomaly  gravity data for configuration definition and approximate depth estimate of tectonic lineaments in the central portion of the Equatorial Atlantic African region. Based on many trials for the most appropriate deconvolution parameters, the best Structural Index and Window Size adopted were 1.0 and 10 respectively and depth solutions were obtained to the depth of 45,000 m. Although, shallow crustal lineaments could not be mapped due to the resolution of the data (5' x 5' grid), good solution clusters of mid-range and deeper lineaments were obtained. The Euler solution clusters showed a largely curvi-linear trend and predicted vertical crustal movement along these lineaments (curvi-lineaments) at deep depths. It also predicted the existence of a micro-basin within the Niger Delta in Agbor region. The lineament networks comprised of major lineament frames to which the minor lineaments were appended and were observed to enter into the continent from the oceanic region mainly  through the Chain, Charcot and the Fernando Po Fracture zones which were already established fracture zones within the Equatorial Atlantic Oceanic region. The major lineaments were oriented in the NE-SW direction while the minor lineaments had orientations ranging from ENE-WSW, NW-SE, to approximately NNW-SSE.  Volcanism was also noted to be closely associated with the mapped lineaments. The study concluded that the study area was largely sheared and severely traversed by the extension of the Equatorial Atlantic rift system whose development was precursor to the opening of the Equatorial Atlantic Ocean.

Keywords: Euler Deconvolution, Tectonic Lineaments, Rift, Asthenosphere,  Isostatic Adjustment.