Recognizing attributes and oomoldic porosity development in eolianite in an arid setting: An example from the quaternary eolianite from the Arabian Gulf coastline, Saudi Arabia

• Autores: Mahbub Hussain
• Localización: Carbonates and Evaporites, ISSN 0891-2556, Vol. 21, Nº. 2, 2006, págs. 124-132
• Idioma: inglés
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• Resumen

  • The Arabian Gulf coastlines close to the city of Dammam, Eastern Province, Saudi Arabia are characterized by the presence of several NW-SE trending low-lying ridges. One such ridge is located by the Dammam-Khobar Highway at the southern edge of Dammam (26°24.84'N; 50°06.45'E). This ridge is up to 10 m high, and composed of medium to coarse-grained eolianite/oolitic sandstone. Most sections exposed in the ridge consist of SSE-trending cross-bed sets. These sets are typically made up of fine-grained ledgy laminae interbedded with medium to coarse-grained recessed laminae. Based largely on the coast-parallel orientation of the ridges, composition, and dips of the cross-bedded units, these ridges appear to represent Quaternary eolianite as observed along the shorelines of the United Arab Emirates.

    Thin-section petrography and scanning electron microscopic (SEM) studies show that a substantial portion of the ridge ooids are cracked and damaged and lack the central nucleus, while the reminder are characterized by large quartz coated with thin micritic rinds overlain by dogtooth spar. Hollow grains of the ridge sands resemble "eggshells". The high proportion of internal pores, coupled with a high-degree of sorting, "eggshell" breakage, the near absence of intergranular cements, and loose tangential grain-to-grain contacts resulted in high-levels of effective porosity (oo-moldic, skel-moldic, and partially-retained interparticle) of this eolianite. This paper discusses development of oo-moldic porosity development in this eolianite, and suggests two contrasting models: (i) leaching of the nucleus in a highly alkaline diagenetic environment, and (ii) physical abrasion and damage of the oolites while being transported by the prevailing wind.