High Resolution Spatial Models of a High-Relief Carbonate Platform Slope (Early Jurassic, Djebel Bou Dahar, High Atlas, Morocco)

Klaas Verwer¹, Oscar Merino-Tome², Jeroen Kenter³, Giovanna Della Porta², Erwin Adams⁴, Paul (Mitch) Harris⁵, and Ted Playton^6
1Faculty of Earth and Life Sciences, Vrije Universiteit, Amsterdam, Netherlands
²School of Earth, Ocean and Planetary Sciences, Cardiff University, Cardiff, United Kingdom
³Chevron ETC, Voorburg, Netherlands
⁴Shell International Exploration & Production, Rijswijk, Netherlands
⁵Chevron ETC, San Ramon, CA
⁶Jackson School of Geosciences, University of Texas at Austin, Austin, TX

Seismic-scale continuous exposures of a Lower Jurassic (Hettangian-Pliensbachian) carbonate platform (High Atlas, Morocco) provide detailed information on lithofacies and stratal geometries in a slope setting strongly affected by synsedimentary extensional tectonics. Aggradational, backstepping and progradational platform-to-slope transects were characterized by distinct lithological features and stratal patterns, and integrated in a digital outcrop model through digital field technologies (RTK GPS and lidar).

The first stage corresponds to a low-relief carbonate platform, which was affected by block faulting. The second platform stage developed as a retrograding platform and built considerable relief (height-above-basin of > 420 m). Small listric “subsurface” faults affected sedimentation patterns in the middle and lower slope. The third stage involved a major change in focus of sediment deposition, and a time during which the slope was sediment starved. During stage four, following a major backstep, 70-meter high clinoforms prograded across the platform top until reaching the relict platform edge. Deposition reestablished in the slope environment, and a coral-sponge-microbial boundstone-dominated margin formed. The platform was not able to fill the available accommodation space in the basin, and the prograding clinoforms steepened up to dips of 23^o, with a total relief of 460 m. Within the slope environment deposits from stage four are present in the form of channelized olistolith bodies, and coarse sheet-like beds, which are interbedded in thick wedges of fine-grained background sediments and calciturbidites.

The spatial information on sedimentary bodies and stratal anatomy will be used to populate 3D depositional models of a retrograding and prograding margin. A number of deterministic and stochastic realizations of rock type population will be presented.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas