Stratal and Facies Anatomy of a Lower Jurassic High-Rising Carbonate Platform Margin (Jebel Bou Dhar, High Atlas, Morocco)

Verwer, Klaas¹, Giovanna Della Porta², Jeroen Kenter³, Oscar Merino², Ted Playton⁴, Erwin Adams⁵ (1) Vrije Universiteit, Amsterdam, Netherlands (2) Cardiff University, Cardiff, United Kingdom (3) Chevron Energy Technology Company, Voorburg, Netherlands (4) The University of Texas at Austin, Austin, TX (5) Shell International Exploration and Production, Rijswijk, Netherlands

Studies integrating high-resolution 3D lithofacies distributions and stratal geometries in carbonate platforms are uncommon because of scarcity of continuous 3D outcrops. Such a seismic-scale and continuous carbonate-platform outcrop (High Atlas, Morocco) provided discrete study windows in platform and margin were analyzed using DGPS and LIDAR imaging. The Lower Jurassic Jebel Bou Dahar evolved in a rift basin, developed into a flat-topped, high-relief, carbonate platform during the Sinemurian to Pliensbachian and drowned in the lowermost Toarcian. It measures roughly 35 by 4-5 km and is fully exposed as exhumed topography. During the Pliensbachien, the platform develops a self-eroding retrogradational margin, ~450 relief or water depth, in an extensional tectonic setting with active syn-depositional faulting resulting in a completely exposed intact platform, margin, and flank to basin profile. This study focuses on the slope study windows, which measures 2.5 km in length, 1 km in width. Key depositional settings (basin ward direction) are 1) grain-dominated outer platform dipping several degrees up to 15 degrees, 2) margin edge with shallow water coral framestone.and deeper water, sub-photic, wackestone-mudstone with sponges and stromatactoid-like cavities; and 3) a steep (up to 40o degrees) slope dominated by (mega)breccias and grain flow deposits derived from the margin alternating with thin-bedded turbidites and marls reflecting a spatially heterogeneous sedimentation pattern. This project aims to provide precise and accurate spatial information on sedimentary bodies and their stratal geometries in a retrograding carbonate platform margin. The spatially anchored data allows geostatistical analyses for depositional models, sequence stratigraphy, prediction from seismic reflection data, and flow models for hydrocarbon reservoirs.