A Carbonate Sheet Slump From the Jubaila Formation, Saudi Arabia: Slope implications

F.O. Meyer

Saudi Aramco, Box 5000, Geological R&D, X-4800, Dhahran 31311, Saudi Arabia Aramco Geological Research and Development, New Technology Division, March 1999

Sedimentologic investigations on the Jubaila limestone identified a sheet slump in outcrops of the formation at Wadi Labon, Central Saudi Arabia. The exposed portion of the sedimentary deformation zone is only three to five feet thick but covers about a square kilometer. It is bounded below and dissected internally by a complex of sinuous glide planes. The basal decolment is a high-relief surface cut into a Thallasinoides riddled firmground. Internally, glide planes delineate a stack of sedimentary slabs whose shingled arrangement describes an irregular upper surface. Individual sedimentary masses range from a few to tens of feet in length within the stack. They feature strata broken up into more or less discreet tabular, ellipsoidal or wedge-shaped masses of carbonate gravel, sand and lime mud. Distinctive tan-weathering grainstone masses display variable orientations relative to each other and to the horizontal stratification above and below the deformation horizon. Most bodies exhibit some degree of deformation expressed as gentle flexures. Tightly folded "slump balls", contorted or broken muddy strata occurs locally between the sedimentary bodies.

The sheet slump documents a mass wasting event in the upper Jubaila Limestone. Its presence signifies that the Jubaila seafloor sloped at an angle sufficiently steep to allow for the event to take place.

Meyer, F.O., 2000; A carbonate sheet slump from the Jubaila Formation, Saudi Arabia: Slope implications: GeoArabia, v. 5, p. 144-145.