INTEGRATED ANALYSIS OF LOWER CRETACEOUS STRATIGRAPHY AND DEPOSITIONAL SYSTEMS: THE ESSAOUIRA-AGADIR BASIN OF MOROCCO.

Access to files

•   FULL-TEXT.PDF (pdf)

Abstract

This multi-disciplinary study integrates high-resolution field sedimentological analysis, biostratigraphy and chemostratigraphy to build a sequence stratigraphic and biochronostratigraphic framework of the Lower Cretaceous in the Essaouira-Agadir Basin (EAB) of Morocco. The results provide insight into the controls on coarse siliciclastic sediment delivery along the Northwest African passive continental margin. This area lies inboard of an underexplored but potentially prolific hydrocarbon province of the Central Atlantic Margin. Recent and past drilling activity has failed to locate commercial reservoirs, highlighting the poor understanding of timing, location, and controls of sediment distribution. Low-temperature geochronological studies of the hinterland show that provenance terranes have experienced kilometre-scale exhumation during the Late Jurassic and Early Cretaceous. This opens the potential for delivery of a substantial amount of coarse clastic material into the basin. The Lower Cretaceous strata of the west-central EAB, however, is overall characterised by a mud-dominated shelf succession. During the late Barremian to early Aptian, a major shoreline shift placed the shallow marine fluvial transition zone close to the shelf edge. No similar event was recorded throughout the Cretaceous, opening questions on the relative role of eustasy versus tectonics as a driving mechanism along passive margins. Detailed sequence stratigraphic assessment on the migration of the shoreface and deltaic depositional environments across the shelf identified tectonic control in the hinterland as the main factor for progradation of the shoreline. The amplification through a subsequent eustatic sea-level fall shifted the shoreline even further basinward and leads to the development of forced regressive deposits. The upper Barremian to lowermost Aptian is the key interval for coarse siliciclastic sediment delivery offshore in the EAB. Detailed correlations, constrained by the high-resolution biostratigraphy, also give important insight into pre-existing structural domains in the basin. The work reveals the presence of palaeohighs throughout the study area, which interacted with fluvial sedimentation during the regression and influenced sediment dispersal. 14 This work underscores the need for integrated and multi-disciplinary stratigraphic studies to decipher basin evolution and controls on changes in depositional environments. It also questions the paradigm for a largely eustatic control on base-level change along the NW Atlantic margin, adding to the growing body of published literature that identifies a more complex post-rift tectonic history for passive margins.

Additional content not available electronically

Distribution Charts Calcareous Nannofossils and Foraminifera (Chapter 4)

Keyword(s)

Ammonoids; Atlantic Margin; Biostratigraphy; Calcareous Nannofossils; Forced Regression; Formaninifera; Lower Cretaceous; Passive Margin; Sedimentology; Sequence Stratigraphy; Stratigraphy

Bibliographic metadata

Institutional metadata

Record metadata