Structure and variability of Mediterranean outflow water flow recorded in contourite sedimentation in the Gulf of Cadiz and west of Portugal

Author(s): Flood, Roger D.; Ducassou, E.; Covelli, Valentina; Hernandez-Molina, F. J.; Stow, Dorrik A.; Alvarez Zarikian, Carlos A.
Author Affiliation(s): Primary:
Stony Brook University, School of Marine and Atmospheric Sciences, Stony Brook, NY, United States
Universite de Bordeaux I, France
University of London Royal Holloway, United Kingdom
Heriot-Watt University, United Kingdom
Texas A&M University, United States
Volume Title: AGU 2013 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2013; American Geophysical Union 2013 fall meeting, San Francisco, CA, Dec. 9-13, 2013. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Water exchange between the Atlantic Ocean and the Mediterranean Sea has important effects on world hydrography, and the exchange varies on both shorter and longer time scales in response to climate change, sea-level change and tectonic land movements. The modern exchange can be studied with instrumental and observational records, but the longer-term variability of climate and water exchange requires the analysis of sedimentary records. Mediterranean Outflow Water (MOW) has influenced global circulation and climate and created a number of sediment drifts along the continental slope of Iberia. MOW history has been particularly important since the reconnection of the Mediterranean and the Atlantic about 5.3 Ma ago. New information about water exchange comes through study of cores collected from Iberian margin drift deposits during IODP Exp. 339. These cores contain sediments from the last 6.2 Ma in an array of sites. Drift deposits are thick sediment accumulations formed where and when currents flow along the seabed. Drift sediments are primarily muddy but they often include coarser layers which include some silt and sand-sized material which are often termed silty or sandy contourites. Several coarser layers are being studied in detail using high-resolution grain size and CAT scanning techniques, along with the analysis of the sand fraction, supplemented with thin section, X-ray and XRF to characterize the beds and the events which created them. Initial results suggest that many beds are formed of a mixture of finer sediment, often similar in grain size to the sediment deposited before and/or after the silty or sandy contourite, and coarser sediment which often overlaps in grain size with the finer sediment. The coarser sediments may have been deposited during short episodes of higher-speed flow, and later bioturbation has mixed the two grain size populations. Grain-size grading patterns within, and sharp contacts associated with, the coarser contourite layers appear to retain some characteristics of the flow events which formed them. The grain size patterns and other bed characteristics suggest that these silty and sandy contourites provide important information about the both the short-term and long-term history of MOW events. Exp 339 Scientists: Acton, G., Bahr, A., Balestra, B., Flores, J. A., Furota, S., Grunert, P., Hodell, D., Jimenez-Espejo, F., Kim, J. K., Krissek, L., Kuroda, J., Li, B., Llave, E., Lofi, J., Lourens, L., Miller, M., Nanayama, F., Nishida, N., Pereira, H., Richter, C., Roque, C., Sanchez Goñi, M., Sierro, F. J., Singh, A., Sloss, C., Takashimizu, Y., Tzanova, A., Voelker, A., Williams, T., Xuan, C.
Year of Publication: 2013
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Atlantic Ocean; Contourite; Currents; Expedition 339; Gulf of Cadiz; Integrated Ocean Drilling Program; Marine sedimentation; North Atlantic; Northeast Atlantic; Ocean circulation; Ocean currents; Sedimentation
Coordinates: N361605 N373418 W0064700 W0100735
Record ID: 2015031014
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