Sedimentology, Mineralogy and Geochemistry of Al-Awshaziyah Inland Sabkha, Central Saudi Arabia Omar A. Al-Harbi Ghulam Hussain M. Mujtaba Khan Natural Resources and Environment Research Institute, King Abdulaziz City for Science and Technology (KACST), Riyadh, Kingdom of Saudi Arabia In the Kingdom of Saudi Arabia, a rising demand of municipal, agricultural and industrial sectors require better utilization of surface and groundwater resources. Some of the wadi and low depressions in the central Saudi Arabia are covered with salt (Inland sabkha). It is also suspected that the aquifers below receive substan- tial amounts of recharge from the above ground salt flat. It is, therefore, important to investigate the mineralogy and geochemistry of these salt-flats to determine their impact on groundwater chemistry. Al-Awshaziyah inland sabkha is a saline dry=wet land with an area of 18 km 2 in the central Saudi Arabia. The study area was divided into six transverses beginning at a permanent marker. The distance of different profiles ranged between 200–300 m. Soil, groundwater and well water samples were collected for physical and chemical composition. Additionally, differ- ent soil and salt facies were measured in each profile. Three sedimentary facies, viz., silty sand; black mud, and salt facies (from bottom to top) had been delineated. The mineralogy by X-ray diffraction analysis (XRD) for silty-sand facies composed of quartz (25–74%), halite (11–16%), dolomite (5–27%), calcite (4–21%), and gypsum (4–8%); black mud facies composed of quartz (14–16%), halite (25–33%), dolomite (18–25%), calcite (20–25%) and gypsum (8–11%); and salt facies is dominated only by halite (100%). The delineated facies led to highlight the depositional environment; mineralogy and geochemistry were studied. The elemental concentrations of CaO, MgO, K 2 O, Na 2 O, Al 2 O 3 , and SiO 2 have been analyzed in order to understand the element behavior of each delineated sedi- mentary facie of sabkha basin. The geochemistry data reveals that SiO 2 increases with the depth and CaO, MgO, Al 2 O 3 , and K 2 O behave in the reverse with the depth of sabkha sediments. The geochemical data has good correlation with the mineralogy of the same profile. Thus, the relationship has been established for the evolution of sabkha basin on the basis of sedimentary facies, mineralogy, and geochemistry. Keywords inland sabkha, sedimentary facies, mineralogy, geochemistry Received 11 August 2005; accepted 22 November 2005. This work was conducted as part of a project (Grant No. 265-23-ES). Authors are grate- ful to KACST, for providing the laboratories facilities where all the work was carried out. Address correspondence to Ghulam Hussain, Natural Resources and Environment Research Institute, King Abdulaziz City for Science and Technology (KACST), P.O. Box 6086, Riyadh 11442, Kingdom of Saudi Arabia. E-mail: ghussain@kacst.edu.sa Arid Land Research and Management, 20:117–132, 2006 Copyright # Taylor & Francis Group, LLC ISSN: 1532-4982 print/1532-4990 online DOI: 10.1080/15324980500545991 117