IODP Expedition 339 in the Gulf of Cadiz and off West Iberia : decoding the environmental significance of the Mediterranean outflow water and its global influence

Hernández-Molina, F.J., Stow, D., Alvarez-Zarikian, C., Acton, G., Bahr, A., Balestra, B., Ducassou, E., Flood, R., 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., Richter, C., Roque, C., Pereira, H., Fernanda Sanchez Goni, M., Sierro, F.J., Singh, A.D., Sloss, C.R., Takashiminzu, Y., Tzanova, A., Voelker, A., Williams, T., & Xuan, C. (2013) IODP Expedition 339 in the Gulf of Cadiz and off West Iberia : decoding the environmental significance of the Mediterranean outflow water and its global influence. Scientific Drilling, 16, pp. 1-11.

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Abstract

IODP Expedition 339 drilled five sites in the Gulf of Cadiz and two off the west Iberian margin (November 2011 to January 2012), and recovered 5.5 km of sediment cores with an average recovery of 86.4%. The Gulf of Cadiz was targeted for drilling as a key location for the investigation of Mediterranean outflow water (MOW) through the Gibraltar Gateway and its influence on global circulation and climate. It is also a prime area for understanding the effects of tectonic activity on evolution of the Gibraltar Gateway and on margin sedimentation. We penetrated into the Miocene at two different sites and established a strong signal of MOW in the sedimentary record of the Gulf of Cadiz, following the opening of the Gibraltar Gateway. Preliminary results show the initiation of contourite deposition at 4.2–4.5 Ma, although subsequent research will establish whether this dates the onset of MOW. The Pliocene succession, penetrated at four sites, shows low bottom current activity linked with a weak MOW. Significant widespread unconformities, present in all sites but with hiatuses of variable duration, are interpreted as a signal of intensified MOW, coupled with flow confinement. The Quaternary succession shows a much more pronounced phase of contourite drift development, with two periods of MOW intensification separated by a widespread unconformity. Following this, the final phase of drift evolution established the contourite depositional system (CDS) architecture we see today. There is a significant climate control on this evolution of MOW and bottom-current activity. However, from the closure of the Atlantic–Mediterranean gateways in Spain and Morocco just over 6 Ma and the opening of the Gibraltar Gateway at 5.3 Ma, there has been an even stronger tectonic control on margin development, downslope sediment transport and contourite drift evolution. The Gulf of Cadiz is the world's premier contourite laboratory and thus presents an ideal testing ground for the contourite paradigm. Further study of these contourites will allow us to resolve outstanding issues related to depositional processes, drift budgets, and recognition of fossil contourites in the ancient record on shore. The expedition also verified an enormous quantity and extensive distribution of contourite sands that are clean and well sorted. These represent a relatively untapped and important exploration target for potential oil and gas reservoirs.

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ID Code: 69925
Item Type: Journal Article
Refereed: Yes
Keywords: IODP Expedition, Gulf of Cadiz, West Iberian Margin, Mediterranean Outflow Water
DOI: 10.5194/sd-16-1-2013
ISSN: 1816-3459
Divisions: Current > Schools > School of Earth, Environmental & Biological Sciences
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: Copyright 2013 The Author(s)
Copyright Statement: This work is distributed
under the Creative Commons Attribution 3.0 License.
Deposited On: 07 Apr 2014 22:54
Last Modified: 08 Apr 2014 23:53

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