Abstract
The similar to 5.5 km sized Jabal Rayah ring structure located at 28 degrees 39 ' N/37 degrees 12 ' E in Saudi Arabia has been classified as a possible complex impact structure located in flat-lying Paleozoic clastic sediments. Previous, detailed mapping showed that erosional processes led to a relief inversion, with displaced, folded, and faulted blocks of Silurian to Early Devonian strata, interpreted to form a ring syncline, now forming a topographically outstanding, 150 m high ring crest. The drainage toward the center of the structure seems controlled by a set of radial faults. This central part is eroded to the level of the surrounding plateau and partially covered with gravel. Analysis of 28 Qusaiba Formation sandstones showed that at the present outcrop level, the sediments seem devoid of shock features. Measurement of fold axes in the central part of the structure shows radially outward plunging fold axes, becoming steeper toward the center, and also fold axes of other orientation, and folded folds. This fold axis pattern is interpreted as an upward-pointing, kilometer-sized sheath fold. Assuming an impact scenario and using the present size of the structure, the minimum central structural uplift is estimated at similar to 500 m, which is consistent with Qusaiba Formation occupying the center of the ring structure.