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अमूर्त

The Change in Fluvial System from Braided to the Meandering Streams in Shendi Formation Central Sudan: An Approach for New Lithostratigraphic Units

Abdelrhim Eltijani

Detailed facies analysis of Shendi formation in the Shendi-Atbara basin displays identical assemblage of sedimentary features and; texture and structure that suggest fluvial depositional environment mainly braided and meandering rivers. Through detailed field investigation, including stratigraphic section logging, facies analysis, analysis of architectural elements and petrographic analysis. Five lithofacies associations were identified; Facies Association LFA1, Facies Association LFA2, Facies Association LFA3, Facies Association LFA4, Facies Association LFA5 and five architectural elements were also reported. These facies associations and fluvial architecture illustrate the two different fluvial environments of deposition; (multi- braided complex braided and channels in El Musawart, shifted into the meandering system at Bagrawia and Umm Ali area. Accordingly, three different lithostratigraphic units of Shendi Formation have been proposed; El Muswarat Sandstone (proximal fluvial), Um Ali-Bagrawia Sandstone (distal fluvial), and the Chert-Conglomerate unit representing the upper unit in the succession. However, the result is also supported by the spatial distribution and paleocurrent data indicate studied sediments have been derived from east and southeast to the basin.