Some Microfacies Characteristics of Tuwaiq Mountain Limestone (Upper Jurassic) in Central Tuwaiq Mountains PDF

Keywords

geology, Saudi Arabia, limestone

Abstract

A complete section of the Tuwaiq Mountain Limestone (upper Jurassic) was measured along a new road cut through the Tuwaiq Mountain escarpment between Riyadh and Al Mizahmia to the west. The section is 193 meters thick. The lower 103.3 meters of the section are designated as the Lower Tuwaiq Mountain Limestone, and the upper 89.7 meters are designated as the Upper Tuwaiq Mountain Limestone. Incomplete sections in the Upper Tuwaiq Mountain Limestone were also measured at the Old Darb Al Hijaz to the north of the main complete section and at Wadi Nisah to the south. These are 49.3 m and 27 m thick, respectively. The Lower Tuwaiq Mountain Limestone is characterized by alternating light yellow, spicular biomicrites and light gray, pelletiferous biomicrites. The Upper Tuwaiq Mountain Limestone comprises light gray, hard, ledge forming biomicrites with abundant corals, stromatoporoids and algae. The microfacies of the Tuwaiq Mountain Limestone are the product of carbonate deposition in two major carbonate environments that prevailed successively over the flooded Arabian Platform. The first represented a calm and sheltered seafloor that was subject to periodic agitation, whereas the second had more open marine conditions. The final phase of deposition was particularly characterized by abundant blue green and dasycladacean algae