Evolution of the Gulf of Cadiz and west Portugal contourite depositional system; tectonic, sedimentary and paleoceanographic implications from IODP Expedition 339

Author(s): Hernández Molina, Francisco-Javier; Sierro, Francisco Javier; Llave, E.; Roque, Cristina; Stow, Dorrik A. V.; Williams, T.; Lofi, Johanna; van der Schee, Marlies; Arnáiz, A.; Ledesma, S.; Rosales, Carlos; Rodriguez-Tovar, Francisco Javier; Pardo-Igúzquiza, Eulogio; Brackenridge, Rachel E.
Author Affiliation(s): Primary:
Royal Holloway University of London, Earth Sciences, Egham, United Kingdom
Other:
University of Salamanca, Spain
Instituto Geológico y Minero de España, Spain
Instituto Dom Luiz, Portugal
Heriot-Watt University, United Kingdom
Lamont-Doherty Earth Observatory, United States
Géosciences Montpellier, France
Repsol, Spain
Gas Natural Fenosa, Spain
University of Granada, Spain
Shell International Exploration & Production, Netherlands
Volume Title: AGU 2015 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2015; American Geophysical Union 2015 fall meeting, San Francisco, CA, Dec. 14-18, 2015. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The contourite depositional systems (CDS) along the southwestern Iberian Margin (SIM) bear the unmistakable signal of Mediterranean Outflow Water (MOW) exiting the Strait of Gibraltar. This locality records key information concerning the effects of tectonic activity on margin sedimentation, the effects of MOW dynamics on Atlantic circulation, and how these factors may have influenced global climate. The Integrated Ocean Drilling Program (IODP) Expedition 339 recently drilled five sites in the Gulf of Cadiz and two sites on the western Iberian margin. The integration of core and borehole data with other geophysical databases leads us to propose a new stratigraphic framework. Interpretation of IODP Exp. 339 data along with that from industry sources and onshore outcrop analysis helps refine our understanding of the SIM's sedimentary evolution. We identify significant changes in sedimentary style and dominant sedimentary processes, coupled with widespread depositional hiatuses along the SIM. Following the 4.5 Ma cessation of a previous phase of tectonic activity related to the Miocene-Pliocene boundary, tectonics continued to influence margin development, downslope sediment transport and CDS evolution. Sedimentary features indicate tectonic pulses of about 0.8 Ma duration with a pronounced overprint of ≈2 -2.5 Ma cycles. Two major compressional events affecting to the Neogene basins at 3.2-3 Ma and 2-2.3 Ma help constrain the three main stages of CDS evolution. The stages include: 1) the initial-drift stage (5.33-3.2 Ma) with a weak MOW, 2) a transitional-drift stage (3.2-2 Ma) and 3) a growth-drift stage (2 Ma-present time) with enhanced MOW circulation and attendant contourite development due to greater bottom-current velocity. Two minor Pleistocene discontinuities at 0.7-0.9 Ma and 0.3-0.6 Ma record the effects of renewed tectonic activity on basin evolution. This research identifies time scales of tectonic controls on deep-marine sedimentation, specifically over periods of 2.5->0.4 Ma Shorter term climatic (orbital) mechanisms control sedimentation at time scales of ≤0.4 Ma. The role of bottom water circulation in shaping the seafloor and controlling the sedimentary stacking pattern on continental margins has to be seriously reconsidered in future studies.
Year of Publication: 2015
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Andalusia Spain; Atlantic Ocean; Cadiz Spain; Contourite; Cores; Europe; Expedition 339; Gulf of Cadiz; Iberian Peninsula; Integrated Ocean Drilling Program; Marine sediments; North Atlantic; Paleo-oceanography; Portugal; Sediments; Southern Europe; Spain; Strait of Gibraltar; Tectonics
Coordinates: N361605 N373418 W0064700 W0100735
Record ID: 2016075300
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