A NEW GEOLOGICAL MAP OF WADI SIATIN BASED ON FIELD MAPPING AND HIGH-RESOLUTION SATELLITE IMAGERY, RED SEA COAST, EGYPT

We present a new geological map of the coastal region between Wadi Siatin and Wadi El Quseir El Qadim, north of Quseir. This study has been carried out in order to assess the hazard potential of occasional flash floods affecting touristic development activities in this area. Based on fieldwork and the evaluation of high-resolution Quickbird satellite imagery with a spatial resolution of 0.6 m, we produced a significantly improved geological map in contrast to the previously available geological maps and topographic data of the area (1: 50 000 and contour intervals of 20 m) . Due to the arid climate conditions and a lack of vegetation, the exposure of rock units and structures is excellent. Our mapping covered a ~7 km wide E-W strip from basement rock exposures to Holocene coastal terraces. We were able to identify five generations of Quaternary coral reef terraces at elevations of 0.5 m, 1-2 m, 4-6 m, 10-12 m, and 20-28 m (a.s.l.). These terraces are mostly covered with a thin veneer of alluvial deposits, and show three sets of fault systems, which are striking NNW, NW and NE. The coastal plain exposes sedimentary rock units of Tertiary and Quaternary age. The Tertiary rocks are represented by sandstone, lime-grit, conglomerate, carbonate, and gypsum. The Quaternary rocks are composed of wadi and terrace deposits, consisting of sand, pebbles, and few boulders. We observed fluvial incision of up to ~50 m of Wadi Siatin into Tertiary sedimentary rocks. Alluvial deposits in the mapping area and especially on top of the coastal terraces show that there has been eastward transport of material towards the coastal resorts, and therefore seasonal flooding might be expected. Further investigations of the distribution of alluvial sediments will enable us to determine vulnerable areas to flash flooding events. These data will be important for further economic development of the area, and may lead to identification of regions that are prone to flooding hazards.