Facies analysis of the Quaternary fluvial system of Khor Eit, Red Sea coast, Sudan

Abstract

This research article is a field-oriented facies analysis of Quaternary fluvial sediments of the ephemeral braided stream Khor Eit, located on the Sudanese Red Sea coast north of Port Sudan town. Although these sediments represent the main groundwater aquifers of the Red Sea coast of the Sudan, they have attracted less geoscientific attention. The present study is intended to fill part of this gap. Eleven fluvial facies were identified: three gravel facies, six sand facies and two mud facies. Based on the downstream geomorphic variation and systematic changes in the facies distribution, the study divides the Khor Eit into a proximal, middle and distal part. The high-energy flow regime in the proximal part is reflected in a characteristic fluvial facies association of channelized, sheet-like and erosive channelized gravel bodies and horizontally stratified gravels of the gravel bars. In the middle part, where the general slope becomes gentler, the facies display distinct fining-upwards dominated by scour-fill facies associations and elongated sheet-like interlayered sand dominated bodies. The fluvial sedimentation in the distal part is characterized by sheet-flood, and low-water accretionary deposits of thin interlayered sand and mud, and the mud drape facies associations. The analysis of the sedimentary architectural elements of the Khor Eit identified six major architectural elements: Gravel bars and bedforms (GB), Channels (CH), Sediment gravity flows (SG), Sandy bedforms (SB), Laminated sand sheets (LS) and Overbank fines (FF). Factors controlling sedimentation processes in the study area (rainfall, morphological aspects and vegetation cover) have been discussed. Identification and detailed documentation of the different fluvial facies types, facies associations the and the study of their lateral and vertical changes downstream allow the construction of a fluvial facies model for khor Eit.