Source of the aeolian dune sand of Toshka area, southeastern Western Desert, Egypt

Abstract

Sedimentological, mineralogical and geochemical investigations were carried out in order to identify the probable source and mode of origin of the aeolian dune sand of the Toshka area at southeastern Western Desert, Egypt. A hundred and thirty sand samples were collected from the base, crest and slip face of barchan and linear dunes together with windward and interdune area and from lee dunes and sand shadows. Grain size analysis of the collected sediments shows that most of the aeolian sand is generally fine-grained, moderately well sorted, fine skewed and leptokurtic. The anchored dunes (lee and sand shadows) are nearly similar and are the finest and best sorted of all the dune types of Toshka sands. Barchans are coarser while the linear dunes represent the least sorted dune sand. The textural, mineralogical and the geochemical results supported by statistical approach indicate that the Toshka sands were mainly derived from late Pleistocene dune sand with a minor contribution from local sources (Pleistocene alluvial sand and Holocene playa). These sands represent the proposed sources probably derived from the weathering of the Nubian sandstone since the mid-Tertiary by fluvial streams and lakes during earlier humid periods and by aeolian processes during arid periods.