A segmented source-to-sink study of an intricate “passive” continental margin. A case study from the Atlantic of NW Africa, Morocco.
Source-to-sink studies are a relatively novel concept which helps to assess complete sedimentary systems from continental catchment area towards the deepwater basin plains. Deepwater clastics are the main exploration target offshore Morocco but have yet to be located correctly. Furthermore Bertotti & Gouiza (2012) pointed out unexpected behaviour of the far from passive margin. Jurassic-Cretaceous exhumation of 2 to 3 km in the eastern Central Atlantic margin and associated increased subsidence in the developing deepwater basin is shown. This highlights some of the intricate processes that were at work and show the complexity of large-scale studies, which clearly require more thorough investigation.
Source-to-sink segment studies are best applied where a clear division from catchment to deepwater deposits is possible. Well-exposed Early Cretaceous outcrops along the Moroccan Atlantic passive margin, rare deepwater outcrops of the Canary Islands, new and existing apatite fission track and (U-Th)/He data, and extensive seismic data coverage allow such a detailed segmented analysis.
Onshore continental to shelf area sediments are very-well exposed and are being worked by two linked studies in the Agadir-Essaouira Basin and the Souss-Tarfaya Basin by T. Luber and A. Arantegui, respectively.
Fluvio-marine deposits, characterised by significant laterally and temporal variability, are exposed in the Agadir-Essaouira Basin. They comprise dominantly fine-grained deposits an periods of coarse-siliciclastic to mixed carbonate/siliciclastic deposition. Predicted offshore, equivalent aged turbiditic deposits seem to have been fed by discrete feeder systems controlled by palaeotopography, tectonic and simultaneous active salt movement.
In the Souss-Tarfaya Basin more proximal depositional environment can be identified with thick-siliciclastic fluvial successions of cross-bedded sandstones, passing basinwards to shallow marine sandstones, sand-rich carbonates and dark clays (Tan-Tan System) in the Tan-Tan region and polymictic breccias interbedded with red sandstones continental alluvial deposits of red sandstones in the Sidi Ifni region.
In Fuerteventura the otherwise inaccessible deep basin deposits have been uplifted and exposed in a rather complex succession of outcrops. Adequate outcrops where located and a high-resolution stratigraphic log was produced.
Outcrop data will be incorporated as boundary parameters into the source-to-sink numerical and conceptual models developed by R. Charton. Further, Apatite fission track and (U-Th)/He analysis are used to constrain the amplitude, rate, and wavelength of the Late Jurassic to Early Cretaceous vertical movements in the source area.
These integrated studies will be reducing risks for locating valuable plays and sedimentary systems for oil and gas exploration.
AAPG Datapages/Search and Discovery Article #90226 © 2015 European Regional Conference and Exhibition, Lisbon, Portugal, May 18-19, 2015