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

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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The contourite depositional system of the Gulf of Cádiz: A sedimentary model related to the bottom current activity of the Mediterranean outflow water and its interaction with the continental margin

Deep Sea Research Part II Topical Studies in Oceanography ◽

10.1016/j.dsr2.2006.04.016 ◽

2006 ◽

Vol 53 (11-13) ◽

pp. 1420-1463 ◽

Cited By ~ 151

Author(s):

F.J. Hernández-Molina ◽

E. Llave ◽

D.A.V. Stow ◽

M. García ◽

L. Somoza ◽

...

Keyword(s):

Continental Margin ◽

Bottom Current ◽

Gulf Of Cadiz ◽

Mediterranean Outflow Water ◽

Sedimentary Model ◽

Current Activity ◽

Depositional System ◽

Gulf Of Cádiz ◽

Mediterranean Outflow ◽

The Mediterranean

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Benthic foraminifera as tools to distinguish contourites and turbidites

10.5194/egusphere-egu21-2702 ◽

2021 ◽

Author(s):

Johanna Schmidt ◽

Anna Saupe ◽

Jassin Petersen ◽

André Bahr ◽

Patrick Grunert

Keyword(s):

Diagnostic Criteria ◽

Coarse Grained ◽

Bottom Current ◽

Gulf Of Cadiz ◽

Sedimentary Processes ◽

Bottom Currents ◽

Mediterranean Outflow Water ◽

Gulf Of Cádiz ◽

Mediterranean Outflow ◽

Del Rio

Contourites occur where along-slope bottom currents induce large accumulations of sediments in the deep sea (Faug&#232;res and Stow, 2008). Distinguishing among contourites and other depositional facies on continental slopes is fundamental for paleoenvironmental reconstructions like bottom current velocities. Nonetheless, reliable and easily applicable diagnostic criteria to properly differentiate between contourites and other coarse-grained and/or graded deep-water deposits such as turbidites are still sparse (e.g., de Castro et al., 2020). The differentiation and interpretation of these deposits is particularly complex in areas where downslope and along-slope sedimentary processes co-occur.The SW Iberian Margin represents an ideal natural laboratory to study the complex interaction of downslope and along-slope processes. Persistent bottom current activity of Mediterranean Outflow Water (MOW) since the early Pliocene (Garc&#237;a-Gallardo et al., 2017) resulted in the deposition of thick contourite drift bodies in the Gulf of C&#225;diz (Hern&#225;ndez-Molina et al., 2014). At the same time, downslope transport, channeled through submarine canyons, occurs frequently. Extensive turbidite intervals - intercalated between contouritic layers and often reworked by bottom currents - have been identified in several Pleistocene and Pliocene sediments in this area (Stow et al., 2013).The aim of this study is to define diagnostic criteria to differentiate normally graded contourites and turbidites as well as reworked turbidites based on microfaunal analyses. Benthic foraminiferal assemblages along Pleistocene contouritic (~0.5 Ma) and turbiditic (~0.9 Ma, ~1.1 Ma) sequences in the Gulf of C&#225;diz (IODP Site U1389) are evaluated to test if their faunal composition provides a reliable tool to distinguish these deposits and the underlying sedimentary processes.&#160;&#160;&#160;References:de Castro, S., Hern&#225;ndez-Molina, F.J., de Weger, W., Jim&#233;nez-Espejo, F.J., Rodr&#237;guez-Tovar, F.J., Mena, A., Llave, E., Sierro, F.J., 2020. Contourite characterization and its discrimination from other deep&#8208;water deposits in the Gulf of Cadiz contourite depositional system. Sedimentology. https://doi.org/10.1111/sed.12813Faug&#232;res, J.C., Stow, D.A.V., 2008. Contourite Drifts. Nature, Evolution and Controls. Dev. Sedimentol. 60, 257&#8211;288. https://doi.org/10.1016/S0070-4571(08)10014-0Garc&#237;a-Gallardo, &#193;., Grunert, P., Voelker, A.H.L., Mendes, I., Piller, W.E., 2017. Re-evaluation of the &#8220;elevated epifauna&#8221; as indicator of Mediterranean Outflow Water in the Gulf of Cadiz using stable isotopes (&#948;13C, &#948;18O). Glob. Planet. Change 155, 78&#8211;97. https://doi.org/10.1016/j.gloplacha.2017.06.005Hern&#225;ndez-Molina, F.J., Llave, E., Preu, B., Ercilla, G., Fontan, A., Bruno, M., Serra, N., Gomiz, J.J., Brackenridge, R.E., Sierro, F.J., Stow, D.A.V., Garc&#237;a, M., Juan, C., Sandoval, N., Arnaiz, A., 2014. Contourite processes associated with the Mediterranean Outfl ow Water after its exit from the Strait of Gibraltar: Global and conceptual implications. Geology 42, 227&#8211;230. https://doi.org/10.1130/G35083.1Stow, D.A.V., Hern&#225;ndez-Molina, F.J., Llave, E., Bruno, M., Garc&#237;a, M., D&#237;az del Rio, V., Somoza, L., Brackenridge, R.E., 2013. The Cadiz Contourite Channel: Sandy contourites, bedforms and dynamic current interaction. Mar. Geol. 343, 99&#8211;114. https://doi.org/10.1016/j.margeo.2013.06.013

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Latest Miocene restriction of the Mediterranean Outflow Water: a perspective from the Gulf of Cádiz

Geo-Marine Letters ◽

10.1007/s00367-021-00693-9 ◽

2021 ◽

Vol 41 (2) ◽

Author(s):

Zhi Lin Ng ◽

F. Javier Hernández-Molina ◽

Débora Duarte ◽

Francisco J. Sierro ◽

Santiago Ledesma ◽

...

Keyword(s):

Mass Exchange ◽

Water Mass ◽

Atlantic Water ◽

Meridional Overturning Circulation ◽

Gulf Of Cadiz ◽

Mediterranean Outflow Water ◽

Gulf Of Cádiz ◽

Mediterranean Outflow ◽

The Mediterranean ◽

Water Mass Exchange

AbstractThe Mediterranean-Atlantic water mass exchange provides the ideal setting for deciphering the role of gateway evolution in ocean circulation. However, the dynamics of Mediterranean Outflow Water (MOW) during the closure of the Late Miocene Mediterranean-Atlantic gateways are poorly understood. Here, we define the sedimentary evolution of Neogene basins from the Gulf of Cádiz to the West Iberian margin to investigate MOW circulation during the latest Miocene. Seismic interpretation highlights a middle to upper Messinian seismic unit of transparent facies, whose base predates the onset of the Messinian salinity crisis (MSC). Its facies and distribution imply a predominantly hemipelagic environment along the Atlantic margins, suggesting an absence or intermittence of MOW preceding evaporite precipitation in the Mediterranean, simultaneous to progressive gateway restriction. The removal of MOW from the Mediterranean-Atlantic water mass exchange reorganized the Atlantic water masses and is correlated to a severe weakening of the Atlantic Meridional Overturning Circulation (AMOC) and a period of further cooling in the North Atlantic during the latest Miocene.

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