Delineation of paleolakes in the Sinai Peninsula, Egypt, using remote sensing and GIS A. Gaber a, * , E. Ghoneim b , F. Khalaf a , F. El-Baz b a Faculty of Science at Port-Said, Suez Canal University, Egypt b The Center for Remote Sensing, Boston University, 725, Commonwealth Avenue #433, Boston, MA 022151, USA article info Article history: Received 23 October 2007 Received in revised form 23 April 2008 Accepted 21 August 2008 Available online 15 October 2008 Keywords: Groundwater significance Lacustrine deposits Mechanism of deposition Source SRTM abstract Well-stratified lacustrine deposits of clay, silt, and marl occur within the rugged mountainous triangle of igneous and metamorphic rocks of Sinai Peninsula, Egypt. These deposits occur only in two sites along Wadi Feiran channel (Feiran and El-Tarfa Oases), where very dense acidic dykes intersect their stream courses. Such dykes played an important role in damming water from torrential rainfall during the humid period to form lakes. The SRTM (90 m) data and high-resolution images (IKONOS) have been utilized to reconstruct the paleolakes in terms of shape, size and water volume. Results show that lake deposits are located where acidic dykes cross narrow channel of high sinuosity. At their former heights, the dykes dammed the surface runoff, thus, three local freshwater paleolakes formed behind them. GIS analysis shows that the largest of these paleolakes was formed in the area of Feiran Oasis. Two other smaller paleolakes were formed at El-Tarfa Oasis due to the presence of two pronounced acidic dykes. These lake deposits were derived mainly from El-Tih Plateau via Wadi El-Akhdar. Another source of these deposits could have been a thin sedimentary cap over the weathered granites northeast of Feiran basin. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Feiran basin is situated in the southwestern part of the Sinai Peninsula, Egypt, covering an area of about 1851.5 km 2 . The basin is a part of the rugged mountainous triangle of igneous and meta- morphic rocks, which dominate the south Sinai region. This basin is dissected by number of wadis, which drain towards the Gulf of Suez in the west, e.g., Feiran, El-Akhdar, El-Sheikh and Solaf. Lacustrine deposits are located only at Feiran and El-Tarfa Oases. These deposits have attracted the attention of geoscientists for over 100 years. They have studied the outcrops of these deposits in order to identify their type, origin and mechanism of deposition (e.g., Abdel- Mogheeth and Himida, 1998; Awad, 1953; Barron, 1907; El-Ghawaby et al., 1983; Gladfelter, 1988; Issar and Eckstein, 1969; Kassem, 1981; Konrad et al., 2004; Kusky and El-Baz, 2000). Barron (1907) was the first to identify these lacustrine deposits and recorded that Plio-Pleistocene lakebed sediments occur in Feiran basin of southwestern Sinai, where erosionally resistant dykes formed dams in steep-walled bedrock canyons. These lacustrine deposits are composed of well-stratified thin beds of silts, clays, marls, and sands. Thin gravel beds are found along the margins of the basin between the silty and marly layers (El-Ghawaby et al., 1983). At the eastern edge of Feiran Oasis, the wadi widens to a circle-like basin, where the lacustrine deposits of about 30 m thickness are exposed. Similarly, at the upstream of Wadi El-Sheikh these beds are exposed between El-Tarfa and Watia pass (Issar and Eckstein, 1969). The abundance of freshwater flora, marl deposits, and the lack of evaporites shows that such deposits formed in large freshwater lakes at the environs of Feiran and El-Tarfa Oases under very humid conditions during the Late Pleistocene time (Awad, 1953). The significant difference in altitude between the lacustrine beds in El- Tarfa and Feiran, and the almost lack of such beds along the channel course between these sites rules out the notion of forming one large paleolake, but local conditions promoted impoundment. The source of these lacustrine deposits has not been discussed in detail before and still under discussion. However, most authors believe these deposits to have formed as lacustrine deposits (for a detailed bibliography see Awad, 1953; Barron, 1907; Gladfelter, 1988; Issar and Eckstein, 1969; Kusky and El-Baz, 2000). On the other hand, Konrad et al. (2004) stated that these deposits are alluvial loess based on Miocene foraminifera embedded in some of the silts around the oasis of Feiran. The origin of the aeolian material can be traced back to the Gulf of Suez, after sedimentation along the slopes of wadis: Feiran, El-Sheikh, and Solaf. The deposits were later washed out by rain, transported by a meandering river and sedimented as overbank fines and crevasse splays, next to coarser material. The authors of the current work support the idea of lacustrine deposit mechanism according to the field inves- tigations (facies of stagnant fresh water) as well as the locations of * Corresponding author. Geology Department, Faculty of Science at Port-Said, Suez Canal University, Egypt. Tel.: +2 010 5129693. E-mail address: ahmedgaber_881@hotmail.com (A. Gaber). Contents lists available at ScienceDirect Journal of Arid Environments journal homepage: www.elsevier.com/locate/jaridenv 0140-1963/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.jaridenv.2008.08.007 Journal of Arid Environments 73 (2009) 127–134