%0 Journal Article
%T Structural Interpretation of the Mamfe Sedimentary Basin of Southwestern Cameroon along the Manyu River Using Audiomagnetotellurics Survey
%A Jean Jacques Nguimbous-Kouoh
%A Eric M. Takam Takougang
%A Robert Nouayou
%A Charles Tabod Tabod
%A Eliezer Manguelle-Dicoum
%J ISRN Geophysics
%D 2012
%R 10.5402/2012/413042
%X Five audiofrequency magnetotelluric AMT soundings were collected northwest-southeast along the Manyu river in the Mamfe sedimentary basin of southwestern Cameroon. The soundings were performed with frequencies in the range 3 to 2500£¿Hz and covered a distance of approximately 28£¿km. Sounding curves and geoelectric and geological sections were processed, and the results were compared with rocks' resistivity to characterize the lithostratigraphy of the eastern part of the basin. The results show above 1000£¿m depth, sedimentary layers with resistivities in the range of 1 to 100£¿Ohm-m, which decrease with depth. We identified three types of sedimentary rocks: laterite-clay mixture, shale, and sandstones. Various faults were also identified, illustrating the structural complexity of the Mamfe basin, along the Manyu River. 1. Introduction The geological studies of the Mamfe basin (southwestern Cameroon) were carried out for the first time by Le Fur [1], Dumort [2], and Paterson et al. [3]. These initial studies provided the framework for the first geological map of the area. The geophysical studies in the area integrate gravity works by Collignon [4], Fairhead and Okereke [5], Fairhead and Okereke [6], Fairhead et al. [7], Ndougsa-Mbarga [8], and Ndougsa-Mbarga et al. [9]. The geophysical studies also include audio-magnetotelluric (AMT) works by Manguelle-Dicoum et al. [10], Nguimbous-Kouoh [11], Nouayou [12], and Tabod et al., [13] to map subsurface resistivities. The aim of this paper is to use AMT field data to characterize the shallow structure of the Mamfe sedimentary basin along the Manyu River. To achieve this, various interpretation techniques were employed. The sounding curves were interpreted to derive the stratigraphy under each AMT station. A pseudosection and geoelectric and geological resistivity sections were then derived along the AMT profile, to deduce the continuity of the subsurface layers and the distribution of associated electrical resistivities. The combination of geoelectrical sections and pseudosections enables a more thorough interpretation [11, 14¨C18]. The AMT profile has five stations: Ndwap (M1), Abonando (M2), Esagem1 (M3), Esagem2 (M4), and Baku (M5). 2. Geology of the Study Area The Mamfe sedimentary basin is a rifting basin formed in response to the Gondwana break-up and subsequent separation of the South American and African plates. It lies on an NW-SE trending trough with a length of 130£¿km and a width of 60£¿km and constitutes a small prolongation of the Benue trough where important oil fields have been discovered (Figure
%U http://www.hindawi.com/journals/isrn.geophysics/2012/413042/