The geology and geochronology of Al Wahbah maar crater,Harrat Kishb,Saudi Arabia |
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| Institution: | 1. Geology Research Unit, P.O. Box 888, Taif University, Taif 21974, Saudi Arabia;2. Isotope Geosciences Unit, Scottish Universities Environmental Research Centre, Rankine Avenue, Scottish Enterprise Technology Park, East Kilbride G75 0QF, United Kingdom;1. Instituto de Geofisica, Universidad Nacional Autónoma de México, México, D.F., Mexico;2. Departamento de Ingeniería Civil y Topografía, CUCEI, Universidad de Guadalajara, México;3. Centro Interdisciplinario de Investigación para el Desarrollo Integral Regional, Instituto Politécnico Nacional, Oaxaca, Mexico;4. Programa de Posgrado en Ciencias de la Tierra, Universidad Nacional Autónoma de México, Mexico, D.F., Mexico;5. Universidad Nacional Autónoma de México, D.F., Mexico;1. Department of Microbiology, Government Medical College Hospital, Chandigarh, India;1. Southern Cross GeoScience, Southern Cross University, Military Rd, Lismore, NSW 2480, Australia;2. IRAMAT-CRPAA, Institut de Recherche sur les Archéomatériaux, Centre de Recherche en Physique Appliquée à l''Archéologie, UMR 5060 CNRS, Université Michel de Montaigne Bordeaux 3, Maison de l''Archéologie, 33607 Pessac, France;3. Department of Archaeology, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia;1. Department of Microbiology, Sahyadri Specialty Laboratories, Pune, Maharashtra, India |
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| Abstract: | Al Wahbah is a large (～2.2 km diameter, ～250 m deep) maar crater in the Harrat Kishb volcanic field in western Saudi Arabia. It cuts Proterozoic basement rocks and two Quaternary basanite lava flows, and is rimmed with an eroded tuff ring of debris from the phreatomagmatic explosion that generated the crater. A scoria cone on the northern wall of the crater was dissected by the explosion and exposes a dolerite plug that was intruded immediately prior to crater formation. The dolerite plug yields a 40Ar/39Ar age of 1.147 ± 0.004 Ma. This is the best possible estimate of the time Al Wahbah crater formed. It is a few tens of thousand years younger than the age of the lower and upper basalt flows, 1.261 ± 0.021 Ma and 1.178 ± 0.007 Ma respectively. A dolerite dyke exposed within the basement in the wall of the crater is dated at 1.886 ± 0.008 Ma. This is the most precise age so far determined for the initiation of basaltic volcanism of Harrat Kishb, and confirms that it is significantly younger than the other post-rift volcanic provinces in the region. This study provides constrains the timing of humid climatic conditions in the region and suggests that the Quaternary basaltic volcanism that stretches the length of the western side of the Arabian peninsula may prove to be useful for establishing palaeoclimatic conditions. |
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