--> SILICICLASTIC RESERVOIR DEVELOPMENTS IN THE MOROCCAN ATLANTIC MARGIN AND THE TETHYS RELATED BASINS IN THE MESOZOIC ERATHEM

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SILICICLASTIC RESERVOIR DEVELOPMENTS IN THE MOROCCAN ATLANTIC MARGIN AND THE TETHYS RELATED BASINS IN THE MESOZOIC ERATHEM

Abstract

Due to the ancestral location of Morocco at the junction between the Tethys and the Central Atlantic domains, several eustatic and tectonic controlled siliciclastic reservoir rocks developments occurred almost simultaneously in these two domains during the Mesozoic Erathem. The sediment sources are the Precambrian and Paleozoic sediments, granites and meta-sediments.

The contemporaneous opening of the central Atlantic and the westward spreading of the Tethys Sea way led to deposition of Triassic-Lias fluvial and eolian sandstones in more than fifteen fault bounded grabens and half-grabens, along the Atlantic margin, in the Atlas domain and in the Rif domain. The hydrocarbon accumulations encountered in the Essaouira and the High plateaux basins is a precursor for the Triassic-Lias reservoir rocks exploration in the other similar basins.

The Middle Jurassic fall of the global sea level caused the receding of Atlantic Ocean to the west and the Tethysian Sea to the East. This have resulted in the exposure of the land mass and deposition of fluvial and deltaic systems within the continent and shelf and likely turbidite complexes in the deep basins. The first ones crop out at several locations and have been proven hydrocarbon bearing in subsurface, meanwhile, the turbidites have been inferred from the 3D seismic data in the deep offshore.

The confinement of the Upper Jurassic platforms, was followed by a series of Lower Cretaceous global fall and rise of sea level. The effects of these events are different and seems to be diachronous in the two domains and even from one segment of the Atlantic margin to another, due either to local tectonics (salt) control or diachronism. However, widespread alluvial, fluvial, deltaic and shallow marine siliciclastic sediments have been reported from the outcrops and in sub-surface in Rif and Atlantic domains. The most distinguished ones occurred during the Barremian, the Hauterivian and the Aptian-Albian stages. Lateral age equivalent turbidites have been identified on the seismic data in the offshore.

Simultaneously with the onset of the Alpine Atlasic/Rif inversion and the hinterlands uplifts, during the Upper Cretaceous, siliciclastics shed from the hinterlands have been deposited on the shelves and the basins during the Coniacian and the Maastrichtian mainly.