Deciphering bottom current velocity and paleoclimate signals from contourite deposits in the Gulf of Cádiz during the last 140 kyr: An inorganic geochemical approach

2014 ◽  
Vol 15 (8) ◽  
pp. 3145-3160 ◽  
Author(s):  
André Bahr ◽  
Francisco J. Jiménez-Espejo ◽  
Nada Kolasinac ◽  
Patrick Grunert ◽  
F. Javier Hernández-Molina ◽  
...  
Keyword(s):  
Current Velocity ◽  
Bottom Current ◽  
Gulf Of Cadiz ◽  
Gulf Of Cádiz ◽  
Geochemical Approach

Contourites in the Gulf of Cadiz: a cautionary note on potentially ambiguous indicators of bottom current velocity

2013 ◽  
Vol 33 (5) ◽  
pp. 357-367 ◽  
Author(s):  
Thierry Mulder ◽  
Rim Hassan ◽  
Emmanuelle Ducassou ◽  
Sébastien Zaragosi ◽  
Eliane Gonthier ◽  
...  
Keyword(s):  
Current Velocity ◽  
Bottom Current ◽  
Gulf Of Cadiz ◽  
Cautionary Note ◽  
Gulf Of Cádiz

Patterns of bottom current flow deduced from dune asymmetries over the Gulf of Cadiz shelf (southwest Spain)

2000 ◽  
Vol 164 (3-4) ◽  
pp. 91-117 ◽  
Author(s):  
F.J Lobo ◽  
F.J Hernández-Molina ◽  
L Somoza ◽  
J Rodero ◽  
A Maldonado ◽  
...  
Keyword(s):  
Current Flow ◽  
Bottom Current ◽  
Gulf Of Cadiz ◽  
Gulf Of Cádiz

scholarly journals How deep does sand deposits in the Alentejo basin (Gulf of Cadiz) reach? Evaluating slope stability from bottom-current activities through time

2020 ◽  
Author(s):  
Davide Mencaroni ◽  
Roger Urgeles ◽  
Jonathan Ford ◽  
Jaume Llopart ◽  
Cristina Sànchez Serra ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Sediment Supply ◽  
Excess Pore Pressure ◽  
Bottom Current ◽  
Gulf Of Cadiz ◽  
Strait Of Gibraltar ◽  
Gulf Of Cádiz ◽  
The Stability ◽  
Iberian Margin ◽  
Excess Pore

<p>Contourite deposits are generated by the interplay between deepwater bottom-currents, sediment supply and seafloor topography. The Gulf of Cadiz, in the Southwest Iberian margin, is a famous example of extensive contourite deposition driven by the Mediterranean Outflow Water (MOW), which exits the Strait of Gibraltar, flows northward following the coastline and distributes the sediments coming from the Guadalquivir and Guadiana rivers. The MOW and related contourite deposits affect the stability of the SW Iberian margin in several ways: on one hand it increases the sedimentation rate, favoring the development of excess pore pressure, while on the other hand, by depositing sand it allows pore water pressure to dissipate, potentially increasing the stability of the slope.</p><p>In the Gulf of Cadiz, grain size distribution of contourite deposits is influenced by the seafloor morphology, which splits the MOW in different branches, and by the alternation of glacial and interglacial periods that affected the MOW hydrodynamic regimes. Fine clay packages alternates with clean sand formations according to the capacity of transport of the bottom-current in a specific area. Generally speaking, coarser deposits are found in the areas of higher MOW flow energy, such as in the shallower part of the slope or in the area closer to the Strait of Gibraltar, while at higher water depths the sedimentation shifts to progressively finer grain sizes as the MOW gets weaker. Previous works show that at present-day the MOW flows at a maximum depth of 1400 m, while during glacial periods the bottom-current could have reached higher depths.</p><p>In this study we derived the different maximum depths at which the MOW flowed by analyzing the distribution of sands at different depths along the Alentejo basin slope, in the Northern sector of the Gulf of Cadiz.</p><p>Here we show how changes in sand distribution along slope, within the stratigraphic units deposited between the Neogene and the present day, are driven by glacial – interglacial period alternation that influenced the hydrodynamic regime of the MOW.</p><p>By deriving the depositional history of sand in the Alentejo basin, we are able to correlate directly the influence that climatic cycles had on the MOW activity. Furthermore, by interpreting new multi-channel seismic profiles we have been able to derive a detailed facies characterization of the uppermost part of the Gulf of Cadiz.</p><p>An accurate definition of sand distribution along slope plays an important role in evaluating the stability of the slope itself, e.g. to understand if the sediments may be subjected to excess pore pressure generation. As sand distribution is a direct function of the bottom-current transport capacity, the ultimate goal of this study is to understand how climate variations can affect the stability of submarine slope by depositing contourite-related sand.</p>

Benthic foraminifera as tools to distinguish contourites and turbidites

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

<p>Contourites occur where along-slope bottom currents induce large accumulations of sediments in the deep sea (Faugères 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.</p><p>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 (García-Gallardo et al., 2017) resulted in the deposition of thick contourite drift bodies in the Gulf of Cádiz (Hernández-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).</p><p>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 Cádiz (IODP Site U1389) are evaluated to test if their faunal composition provides a reliable tool to distinguish these deposits and the underlying sedimentary processes.</p><p> </p><p> </p><p> </p><p>References:</p><p>de Castro, S., Hernández-Molina, F.J., de Weger, W., Jiménez-Espejo, F.J., Rodríguez-Tovar, F.J., Mena, A., Llave, E., Sierro, F.J., 2020. Contourite characterization and its discrimination from other deep‐water deposits in the Gulf of Cadiz contourite depositional system. Sedimentology. https://doi.org/10.1111/sed.12813</p><p>Faugères, J.C., Stow, D.A.V., 2008. Contourite Drifts. Nature, Evolution and Controls. Dev. Sedimentol. 60, 257–288. https://doi.org/10.1016/S0070-4571(08)10014-0</p><p>García-Gallardo, Á., Grunert, P., Voelker, A.H.L., Mendes, I., Piller, W.E., 2017. Re-evaluation of the “elevated epifauna” as indicator of Mediterranean Outflow Water in the Gulf of Cadiz using stable isotopes (δ13C, δ18O). Glob. Planet. Change 155, 78–97. https://doi.org/10.1016/j.gloplacha.2017.06.005</p><p>Hernández-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., García, 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, 227–230. https://doi.org/10.1130/G35083.1</p><p>Stow, D.A.V., Hernández-Molina, F.J., Llave, E., Bruno, M., García, M., Díaz del Rio, V., Somoza, L., Brackenridge, R.E., 2013. The Cadiz Contourite Channel: Sandy contourites, bedforms and dynamic current interaction. Mar. Geol. 343, 99–114. https://doi.org/10.1016/j.margeo.2013.06.013</p>

scholarly journals 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

2013 ◽  
Vol 16 ◽  
pp. 1-11 ◽  
Author(s):  
F. J. Hernández-Molina ◽  
D. Stow ◽  
C. Alvarez-Zarikian ◽  
Keyword(s):  
Sediment Cores ◽  
Tectonic Activity ◽  
Bottom Current ◽  
Gulf Of Cadiz ◽  
Climate Control ◽  
Mediterranean Outflow Water ◽  
Depositional Processes ◽  
Current Activity ◽  
Gulf Of Cádiz ◽  
Mediterranean Outflow

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.

Deep-water sediment wave fields, bottom current sand channels and gravity flow channel-lobe systems: Gulf of Cadiz, NE Atlantic

Sedimentology ◽  
2003 ◽  
Vol 50 (3) ◽  
pp. 483-510 ◽  
Author(s):  
Edward L. Habgood ◽  
Neil H. Kenyon ◽  
Douglas G. Masson ◽  
Andrey Akhmetzhanov ◽  
Philip P. E. Weaver ◽  
...  
Keyword(s):  
Deep Water ◽  
Flow Channel ◽  
Gravity Flow ◽  
Bottom Current ◽  
Gulf Of Cadiz ◽  
Ne Atlantic ◽  
Sediment Wave ◽  
Wave Fields ◽  
Gulf Of Cádiz

Erosive sub-circular depressions on the Guadalquivir Bank (Gulf of Cadiz): Interaction between bottom current, mass-wasting and tectonic processes

2016 ◽  
Vol 378 ◽  
pp. 5-19 ◽  
Author(s):  
Marga García ◽  
Francisco Javier Hernández-Molina ◽  
Belén Alonso ◽  
Juan Tomás Vázquez ◽  
Gemma Ercilla ◽  
...  
Keyword(s):  
Bottom Current ◽  
Mass Wasting ◽  
Gulf Of Cadiz ◽  
Tectonic Processes ◽  
Gulf Of Cádiz ◽  
Current Mass

FORMATION HISTORY AND OCEANOGRAPHIC CONTROL OF LATE HOLOCENE MUD DEPOCENTERS IN THE NORTHEASTERN GULF OF CADIZ, SOUTHERN SPAIN

2016 ◽  
Author(s):  
Mary Lee King ◽  
◽  
Till J.J. Hanebuth ◽  
Francisco Lobo ◽  
Hendrik Lantzsch ◽  
...  
Keyword(s):  
Late Holocene ◽  
Southern Spain ◽  
Gulf Of Cadiz ◽  
Formation History ◽  
Gulf Of Cádiz
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