Taoudeni Basin of West Africa

Topics: Sedimentary rock, Precambrian, Carboniferous Pages: 7 (4102 words) Published: October 28, 2014

GEOLOGIC SETTING
The Taoudeni basin is a major sedimentary basin in West Africa, named after the Taoudeni village in northern Mali. It covers large parts of the West African craton in Mauritania and Mali. It is of considerable interest due to its possible reserve of oil. Figure SEQ Figure \* ARABIC 1: WEST AFRICAN MAP SHOWING THE TAOUDENI BASIN

The Taoudeni Basin is an intracratonic sag basin, bounded to the northwest and east by Precambrian basement rocks of the Reguibat massif and Adrar des Iforas, respectively. To the southwest the basin is limited by Precambrian and Paleozoic rocks of the Mauritanides fold belt to the west and by the so-called Pan-African fold belt to the east and to the south and southeast by basement rocks of the Leo uplift. The Pan-African fold belt (650 to 550 Ma) includes the Pharuside fold belt and it extends into the Gourma region, as well as into the Dahomeyide fold belt to the south. To the north, the basin is connected with the Algerian basin complex through the Tannezrouft saddle, to the east with the Niger Basin through the strait of Gao, and to the south with the Bove Basin. The Mauritanide fold belt is of Hercynian age in the north, but includes parts of the Caledonian and Pan-African fold belts in the south.It underlies most of Mali, and extends into Algeria, Burkina Faso, and continuesinto the two Guineas and Senegal in the southwest, where it is known as the Bove Basin. Including its exposed rims, it covers about 975,000km2, approximately half of this area being in Mauritania and the other half in Mali. In central Mauritania, sedimentary rocks are greater than 3km thick (Association of African Geological Surveys, 1968); although, in general, the sedimentary rocks are less than 2 km in most parts of the basin. The central part of the Taoudeni Basin is masked by continental formations of Cretaceous, Tertiary, and Recent age. In Precambrian time the basement surface in West Africa was peneplaned during the course of long continental evolution. Later, this continental paleosurface, characterized by scattered aeolian pebbles (Bongrand and others, 1961), was covered by upper Precambrian through Upper Carboniferous sedimentary rocks. In the Taoudeni Basin, although much faulting occurs (Houghton, 1963), the beds are generally unfolded or gently folded and generally consist of epicontinental marine or continental types of rocks with unconformities and some discordances resulting from minor adjustments of the West African craton (Dillon and Sougy,1974). The stratigraphy along the northwest margin of the Taoudeni Basin was established by Trompette (1969a, 1969b, 1970). TECTONIC EVOLUTIONAccording to Bronner and others (1980), evolution of the cratonicTaoudeni basin was controlled by two main factors: 1. Local occurrence of high-density crustal material in the Lower Precambrian basement, causing local subsidence during the 1,100 to 650 ma period. 2. Regional Pan-African orogeny (650 ma), which caused increased mobility and subsidence of the craton to shape the final form of the basin interior. Thestructural evolution of the Taoudeni Basin initiated via a series of NNE-SSW oriented basementnormal faults and crustal thinning associated with formation of isolated horsts and grabens (Bronner et al., 1980). Proterozoic sedimentation began with continental to marine, dominantlysiliciclastic strata of the Char (in Mauritania) and Douik (in Algeria) groups (Benan and Deynoux, 1998; Rahmani et al., 2009). Present-day exposure of these basal siliciclastic units is restricted to two prominent grabens that intersect the northern edge of the Taoudeni Basin. Thethickness of these units varies dramatically, from 0 to >400 meters in outcrop (Benan and Deynoux, 1998) and can be traced to an unknown extent at depth (Rahmani et al., 2009), reflecting deposition that was controlled by changes in basement topography during extension. A basin-wide unconformity marks the boundary between basal siliciclastic...
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