Sedimentologic Characterization of Postrift Depositional Systems (Tithonian to Albian) from DSDP Leg 41, Site 370 and DSDP Leg 50, Site 416, Deep Water Offshore Morocco
Larry Zarra, Gemma M. Barrie, Shauna K. Oppert, 2015. "Sedimentologic Characterization of Postrift Depositional Systems (Tithonian to Albian) from DSDP Leg 41, Site 370 and DSDP Leg 50, Site 416, Deep Water Offshore Morocco", Petroleum Systems in “Rift” Basins, Paul J. Post, James Coleman, Jr., Norman C. Rosen, David E. Brown, Tina Roberts-Ashby, Peter Kahn, Mark Rowan
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Predicting potential sandstone reservoir character of deep-water sedimentation units in the postrift subsurface section of the Morocco Atlantic coast is problematic as there are only a few deep wells in the area. Two key control points for uppermost Jurassic to Lower Cretaceous deposition in this area are the Deep Sea Drilling Project (DSDP) Leg 41, Site 370 (1975), and DSDP Leg 50 Site 416 (1976) cores. Sites 370 and 416 are located approximately 150 kilometers from the coast of Morocco, and are in 4,200 m of water, at the base of the continental slope. Sedimentologic characterization of cored strata in the 1978 and 1980 DSDP volumes is generalized, and only a few restricted intervals are described in detail.
This study presents results from a new lithologic description of 440 meters of conventional core from Sites 370 and 416. Strata range from Tithonian to Albian in age. Claystone and siltstone are the dominant lithofacies and comprise 91% of the cores. The cores also contain 6.8% sandstone, 1.7% fine-textured carbonate, and 0.6% carbonate grainstone. The focus here is on the sandstone and grainstone.
Sandstone beds are either Bouma turbidites (26.4%) or contourites (73.6%). Sandstone turbidite beds range from centimeter to several decimeters thick, and are not preferentially distributed within the Mesozoic section. Contourite beds are ≤4 cm. Carbonate grainstones occur in Valanginian to Aptian strata. They were deposited as calciturbidites, and contain platform derived carbonate grains. The presence of numerous turbidite beds (>200) distributed throughout the Tithonian to Albian strata suggests the repeated occurrence of throughgoing turbidite fairways on the Morocco Atlantic slope.