Carbonate Sediment-Fill of an Oceanic Shelf, Lower Cretaceous, Arabian Peninsula
T. C. Connally, R. W. Scott, 1985. "Carbonate Sediment-Fill of an Oceanic Shelf, Lower Cretaceous, Arabian Peninsula", Deep-Water Carbonates: Buildups, Turbidites, Debris Flows and Chalks—A Core Workshop, Paul D. Crevello, Paul M. Harris
Download citation file:
The initial Cretaceous relative seA-1evel rise drowned the Late Jurassic shelf on the eastern margin of the Arabian Plate. The consequent marginal shelf basin extended up to 1100 km onto the Arabian platform. During the approximately 13 ma duration of the Berriasian-Valanginian a sediment wedge accumulated up to at least 500 m thick. This represents an average rate of sediment accumulation of 3.85 cm/1000 yrs. Three successive formations represent a filling of this shelf basin by progressively shallower carbonate-producing environments. Sediment on the deepest part of the shelf was silica-rich, radiolarian-calpionellid lime mudstone, the Rayda Formation, which locally is up to 90 m thick. This facies represents deeper, low oxygen oceanic waters that flooded the shelf. Overlying the Rayda and replacing it shelfwards is the Salil Formation, which consists of up to 335 m of argillaceous lime mudstone. Deep bottom currents are indicated by thin density-current deposits.
At the ramp margin ooid and oncoid grainstones of the Habshan Formation accumulated in the zone of wave action. This unit thickens shelfward from about 45 m to more than 180 m in eastern Arabia. Ooid sands accumulated in bars; leeward of the ooid shoals oncoid muddy sands were deposited in the shelf lagoon. Local storm events deposited intra-clastic sediments. Seaward of the shoals, ooids and bioclasts were mixed downslope into the argillaceous lime muds to form the transition with the Salil. Upon the shoals were scattered bioherms and biostromes of corals, stromatoporoids, and caprotinid rudists, the precursors of the caprinids. The Habshan is overlain by dolomitic lime wackestones with monopleurids, requienids, corals, and various foraminifers of the Lekhwair Formation which were deposited in the protected shelf lagoon. The vertical and lateral succession of these facies demonstrate the progradation of the inner ramp shoals over the middle and outer shelf sediments. Age relationships verify the time-transgressive character of the Habshan from the northern United Arab Emirates to Oman.
Figures & Tables
Deep-water carbonates represent on the few frontiers remaining for carbonate exploration and research. The last decade has experienced a rapid evolution in concepts of depositional models and diagenesis which underscores the importance of these deposits as significant reservoirs and source rocks. This workshop displayed cores selected to provide subsurface geologic examples of deepwater carbonates from a variety of depositional settings. Several papers discuss depositional models, platform-to-basin reconstructions, and diagenetic sequences that are important in the development and exploration of Paleozoic carbonate debris flow and turbidite reservoirs of the Palo Duro, Delaware and Midland Basins. Many other examples are included from several different regions.