133,000 Years of Sedimentary Record in a Contourite Drift in the Western Alboran Sea: Sediment Sources and Paleocurrent Reconstruction

The Djibouti Ville Drift is part of a contourite depositional system located on the southern side of the Djibouti Ville Seamount in the Alboran Sea (Western Mediterranean). The sedimentary record of a core located in the drift deposits has been characterized to achieve the possible sediment sources for the Saharan dust supply and the paleocurrent variability related to Mediterranean intermediate waters for the last 133 kyr. Three end-member grain-size distributions characterize the sediment record transported by the bottom current to address the different aeolian populations, i.e., coarse EM1, silty EM2, and fine EM3. For these particles, the most likely source areas are the Saharan sedimentary basins and deserts, as well as the cratonic basins of the Sahara-Sahel Dust Corridor. The prevalence of these main source areas is shown in the core record, where a noticeable change occurs during the MIS 5 to MIS 4 transition. Some punctual sediment inputs from the seamount have been recognized during sea-level lowstand, but there is no evidence of fluvial supply in the drift deposits. The paleocurrent reconstruction allows the characterizing of the stadial and cold periods by large increases in the mean sortable silt fraction and UP10, which point to an enhanced bottom current strength related to intermediate water masses. Conversely, interglacial periods are characterized by weaker bottom current activity, which is associated with denser deep water masses. These proxies also recorded the intensified Saharan wind transport that occurred during interstadial/stadial transitions. All these results point to the importance of combining sediment source areas with major climatic oscillations and paleocurrent variability in palaeoceanographic sedimentary archives, which may help to develop future climate prediction models

Reconstruction of the source areas for the aeolian dust deposited in the contourite drift associated with the submarine seamount Djibouti Ville (Alboran Sea)

Se ha realizado el estudio del registro sedimentario del drift contornítico asociado al monte submarino Villa de Djibouti (mar de Alborán, Mediterráneo occidental) con el fin de reconstruir las áreas fuente de polvo eólico desde el Pleistoceno Superior al Holoceno. Se han podido diferenciar tres end-members (EM1 grueso, EM2 limoso y EM3 fino) que caracterizan la distribución granulométrica de las principales poblaciones de polvo eólico. Las áreas fuente más probables de estas partículas son las cuencas sedimentarias y los desiertos, así como las cuencas cratónicas del corredor Sahara-Sahel, cuya prevalencia en el registro sedimentario experimenta un cambio durante la transición de MIS 5 a MIS 4. Se han reconocido algunos aportes puntuales del monte coincidiendo con periodos de bajada del nivel del mar, pero no se han encontrado evidencias de aportes fluviales en los depósitos contorníticosThe sedimentary record of the contourite drift associated with the Djibouti Ville seamount (Alboran Sea, western Mediterranean) has been studied to reconstruct the source areas of the aeolian dust from Late Pleistocene to Holocene. Three end-member grain-size distributions address for different aeolian populations (coarse EM1, silty EM2 and fine EM3). For these particles, the most probable source areas are the Saharan sedimentary basins and deserts as well as the cratonic basins of the Sahara-Sahel corridor, whose prevalence in the core record changes by the MIS 5 to MIS 4 transition. Some punctual sediment inputs from the seamount have been recognized during sea-level low-stand but there is no evidence for fluvial supply in the drift deposit

De la déchirure continentale à l'accrétion océanique (ouverture du Golfe d'Aden)

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Sci.Terre recherche (751052114) / SudocFONTAINEBLEAU-MINES ParisTech (771862302) / SudocSudocFranceF

Tectonic and stratigraphic evolution of the Western Alboran Sea Basin in the last 25 Myrs

International audienceThe Western Alboran Basin (WAB) formation has always been the subject of debate and considered either as a back-arc or a forearc basin. Stratigraphic analyses of high-resolution 2D seismic profiles mostly located offshore Morocco, enabled us to clarify the tectonic and stratigraphic history of the WAB. The thick pre-rift sequence located beneath the Miocene basin is interpreted as the topmost Malaguide/Ghomaride complex composing the Alboran domain. The structural position of this unit compared with the HP–LT exhumed Alpujarride/Sebtide metamorphic basement, leads us to link the Early Miocene subsidence of the basin with an extensional detachment. Above the Early Miocene, a thick Serravallian sequence marked by siliciclastic deposits is nearly devoid of extensional structures. Its overall landward to basinward onlap geometry indicates that the WAB has behaved as a sag basin during most of its evolution from the Serravallian to the late Tortonian. Tectonic reconstructions in map view and in cross section further suggest that the basin has always represented a strongly subsiding topographic low without internal deformation that migrated westward together with the retreating slab. We propose that the subsidence of the WAB was controlled by the pull of the dipping subducting lithosphere hence explaining the considerable thickness (10 km) of the mostly undeformed sedimentary infill