SEQUENTIAL STRATIGRAPHY OF THE LOWER CARB ONIFEROUS OF THE CENTRAL HIGH ATLAS AND THE JEBILET IN MOROCCO - BASINS WITH TURBIDITES CONTROLLED BY TECTONICS

Marine deposits of Visean age are well exposed in the Marrakesh area. Two third order sequences are identified in the central High Atlas and Jebilet: SA, which is of Middle Visean age (Cf5); SB of Upper Visean age (CfG alpha beta gamma); and a complex with olistoliths of Upper Vi sean-Lower Namurian age (Cf6 delta-Cf7). The SA and SB sequences consi st of a relative low-lying system tract with turbidites, a retrograde transgressive system tract and a prograde high-lying system tract. The relative low level comprises a turbiditic fan fed by tectonic uplift, which does not strictly coincide with eustatic processes. The transgr essive system tract retrogrades firstly on the slope during tectonic r eactivation with slumps, channels and silty levees, secondly on the sh elf edge with a mixture of turbiditic and storm deposits and finally o n the shelf with storm deposits and reef building. The high level syst em tract progrades on the shelf by a delta fan. This model is similar to sequences described in Spain and Italy by Mutti (1992), where tecto nism is dominant. Nevertheless, eustasy, as described by Vail et al. ( 1977) played a part, since the same sequences are found in the chart o f Ross and Ross (1987): S1, which is of Middle Visean age (Cf5) and S2 which is of Upper Visean age (Cf6 alpha beta gamma). Only the compari son between regional sequences described in Morocco and the sequences of the European platform allows tectonics and eustasy to be taken into consideration. (C) 1997 Elsevier Science Limited.