Résumé
The Mediterranean Outflow Water (MOW), modified by paleoceanographic conditions and tectonic processes, played a significant role in the formation of sediments drifts along the Iberian Margin. Using sediment samples from IODP Hole U1387C, we explore the Early Pleistocene history of the upper MOW core above the central Faro Drift in the Gulf of Cádiz. The time series of benthic foraminifer stable isotope and grain size related data have a rigorous stratigraphic framework consisting of nannofossil biostratigraphy and paleomagnetic and δ18O stratigraphy. The paleoenvironmental records are supplemented by natural gamma ray downhole logging data. Above the hiatus associated with the youngest dolostone, sandy to muddy contourite sedimentation started at 1.946 Ma, i.e., within Marine Isotope Stage (MIS) 74, at IODP Site U1387, slightly younger than at IODP Site U1389. Formation of contourite layers, reflected in the sortable silt and sand percentage records, strongly reacted to precession forcing, including semi- and quarter-precession cycles. The majority of the contourite beds developed during stadial (colder) climate periods, like previous observations from the Early to Late Pleistocene. Formation of contourite layers within MIS 53, MIS 55 and MIS 65, however, appear to be linked to the prevailing atmospheric conditions over North Africa. Periods of poor ventilation in the upper MOW were linked to insolation maxima and reduced ventilation in the Mediterranean Sea. Here, MIS 51 presents a peculiar case as poor ventilation reached from the surface to the lower North Atlantic Deep Water range, reflecting unique interglacial conditions that merit future exploration.
•Multi-proxy stratigraphic control for Early Pleistocene record above dolostone.•Early Pleistocene sedimentation at IODP Site U1387 started at 1.95 Ma (MIS 73).•MOW ventilation levels mainly linked to Mediterranean Sea water masses.•Contourite beds formed with semi- to quarter-precession cyclicity.•MIS 51 stands out with unique conditions for δ13C minimum and contourite beds.