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.