S.M. Dini A.M. Farasani G.P. Riddler G.H. Smith M.B. Griffin Marcel Van Eck C. R. Meissner Jr. 1990 <p>The Thaniyat Turayf quadrangle, sheet 29C, lies in the northwestern part of Saudi Arabia near the border with Jordan. The quadrangle is located between lat 29&deg;00'-30&deg;00' N. and long 37&deg;30'-39&deg;00' E. It includes the southwestern rim of the Sirhan-Turayf Basin and is underlain by Silurian to Miocene- Pliocene sedimentary rocks that are partly covered by surficial duricrust, sand, and gravel.</p> <p>Most of the sedimentary rocks of the map area are of marine origin, varying from outer shelf to near-shore and coastal-lagoon environments. Episodes of fluvial-deltaic deposition reflecting marine regression occurred in the Devonian, and continental and lacustrine sedimentation are characteristic of the Miocene.</p> <p>Tensional structures, such as linear- joint fractures, grabens, and block faulting, probably resulted from rifting associated with the opening of the Red Sea.</p> <p>The map area contains the southern part of the Southwestern Area, an important phosphate-rock province that includes the Thaniyat Phosphorite member. Total estimated resources of phosphorite in three select areas of the Thaniyat Phosphorite member are 978,000,000 t with an average grade of 24 percent P₂O₅.</p> <p>A new structural concept introduced in this report extends the Wadi as Sirhan graben complex southeastward into the An Nafud. This concept increases the size of the potentially oil-and-gas-bearing Wadi as Sirhan region to include the An Nafud.</p> application/pdf 10.3133/ofr90259 en U.S. Geological Survey Preliminary geologic map of the Thaniyat Turayf Quadrangle, sheet 29C, Kingdom of Saudi Arabia reports