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Site U13871

Expedition 339 Scientists2

Background and objectives

Integrated Ocean Drilling Program (IODP) Site U1387, located toward the eastern end of Faro Drift (36°48.3210′N, 7°43.1321′W), is one of the most important sites of Expedition 339 (Figs. F1, F4 in the “Site U1386” chapter [Expedition 339 Scientists, 2013c]). It represents an opportunity for recovering a key succession spanning the early Pleistocene, Pliocene, and latest Miocene. In particular, we are interested in the Pliocene record, which should allow us to determine the onset of the upper core of Mediterranean Outflow Water (MOW) and assess its influence on the margin during this period (Fig. F6 in the “Expedition 339 summary” chapter [Expedition 339 Scientists, 2013a]). Site U1387 is ~4.1 km southeast of Site U1386 (Fig. F1 in the “Site U1386” chapter [Expedition 339 Scientists, 2013d] and F12 in the “Expedition 339 summary” chapter [Expedition 339 Scientists, 2013a]).

Opening of the Strait of Gibraltar (or Gibraltar Gateway) had a major impact on both the Alboran Sea and North Atlantic Ocean (Ryan et al., 1973; Duggen et al., 2003; Briand, 2008; García-Castellanos et al., 2009; Estrada et al., 2011; Garcia-Castellanos and Villaseñor, 2011). Opening of the Gibraltar Gateway is documented to have occurred at the end of the Miocene (Berggren and Hollister, 1974; Mulder and Parry, 1977; Maldonado et al., 1999; Estrada et al., 2011). One of its key effects was the initiation of MOW, the timing of which has generally been accepted as coeval with the Strait of Gibraltar opening (Maldonado and Nelson, 1999; Blanc, 2002; Khélifi et al., 2009).

Since the latest Miocene, an oblique compressional regime has regionally developed simultaneously with the extensional collapse of the Betic-Rif orogenic front by westward emplacement of a giant chaotic body known as the Cádiz Allochthonous Unit and by very high rates of basin subsidence coupled with strong diapiric activity (Maldonado et al., 1999; Medialdea et al., 2004, 2009; Zitellini et al., 2009). During the Pliocene and Quaternary, the effect of glacio-eustatic variations partly overprinted structural effects on the margin and resulted in erosion, sedimentary progradation, and incision of major submarine canyons (Mougenot, 1988; Llave et al., 2001, 2007a, 2011; Alves et al., 2003; Terrinha et al., 2003). By the end of the early Pliocene, subsidence decreased and the margin evolved toward its present, more stable conditions (Maldonado et al., 1999; Medialdea et al., 2004; Roque et al., 2012). Some neotectonic reactivation is also evident, as expressed by the occurrence of mud volcanoes and diapiric ridges (Somoza et al., 2003; Fernández-Puga et al., 2007) and fault reactivation (Zitellini et al., 2009). Tectonics have represented a long-term key factor in affecting seafloor morphology, which has exerted strong control on the pathways of MOW and, therefore, on the architecture of the contourite depositional system (CDS) (Llave et al., 2007b, 2011; García et al., 2009; Roque et al., 2012).

Co-eval with the aforementioned tectonic framework, a very large CDS was generated during the Pliocene and Quaternary by the action of MOW on the middle slope of the Gulf of Cádiz. General background about this CDS as well as the Faro Drift was included in “Background and objectives” in the “Site U1386” chapter (Expedition 339 Scientists, 2013d).

Several authors have tried to reconstruct the Pliocene and Quaternary sedimentary stacking pattern and evolution of the large drifts within that CDS (Faugères et al., 1985; Nelson et al., 1999; Llave et al., 2001, 2007a, 2011; Hanquiez et al., 2007; Hernández-Molina et al., 2006, 2009; García et al., 2009; Marchès et al., 2007, 2010; Roque et al., 2012). They have proposed a contourite stacking pattern by different units and subunits depending very much on the resolution degree of their data set. Moreover, there is not a consensus between these authors about

  • The timing of the onset of contourite deposition in the Faro-Albufeira Drift,

  • The detail of evolutionary phases and specifically the nature of evolution during the early and late Pliocene,

  • The age of the different seismic units, and

  • The timing of neotectonic activity.

However, there is consensus about enhanced contourite deposition and marked drift growth during the Quaternary (i.e., after 2.6 Ma). Moreover, these authors have proposed two more phases of current intensification, possibly associated with the mid-Pleistocene revolution (MPR; ~0.9 Ma) and marine isotopic Stage 12 (~0.4 Ma), and inferred that the present drift morphology was developed after the MPR. In addition, most sediments within the drift were deposited by alongslope processes related to MOW, although some turbidite input and downslope processes were suggested by Riaza and Martinez del Olmo (1996), Maldonado et al. (1999), and Roque et al. (2012) for the early Pliocene and by Marchés et al. (2010) for the Quaternary.


The major objective for Site U1387 was to recover a complete sedimentary record for at least the last 5.3 m.y. on the Faro Drift, deposited under the influence of the upper core of MOW.

This record will allow us to investigate

  • The onset of MOW and its relation with the opening of the Gibraltar Gateway,

  • The influence of the Gibraltar Gateway through the Pliocene,

  • MOW paleoceanography and its global climate significance, and

  • The effects of long- and short-term climate and sea level changes on the sediment architecture of the contourite drift.

Specific objectives for Site U1387 include:

  • Drilling through the drift succession and into late Miocene sediments and hence dating the basal age of contourite drift sedimentation in the Gulf of Cádiz;

  • Evaluating the nature of change in the patterns of sedimentation and microfauna from the end of the Miocene through the early to middle Pliocene;

  • Documenting the possible effects of the Gibraltar Gateway through the Pliocene and hence determining the input variation of the influx of warm, saline intermediate water into the North Atlantic Ocean and the nature of change in the patterns of sedimentation and microfauna;

  • Reconstructing the main MOW paleoceanographic events for the Pliocene and identifying the role of salt injection from MOW in the dynamics of North Atlantic Deep Water;

  • Focusing on calibration of facies and the inferred environmental changes in terms of global rapid climatic events;

  • Evaluating the correlation and influence of cold/warm periods with MOW variation, which can test the concept of cold-period intensification of MOW during the Pliocene and early Pleistocene;

  • Determining the sedimentary stacking pattern of Faro Drift in relation to changes in sea level and other forcing mechanisms, determining the potential role of variations in cross-sectional area of the Gibraltar Gateway;

  • Evaluating periods of drift construction, non-deposition (hiatuses) and erosion;

  • Evaluating the contourite deposition in relation to sea level variation and to the further development of a sequence stratigraphic model; and

  • Calibrating and hence understanding the sedimentary cyclicity evident on the deposits, which can characterize their sedimentary expression and regional extent.

1Expedition 339 Scientists, 2013. Methods. In Stow, D.A.V., Hernández-Molina, F.J., Alvarez Zarikian, C.A., and the Expedition 339 Scientists, Proc. IODP, 339: Tokyo (Integrated Ocean Drilling Program Management International, Inc.).

2Expedition 339 Scientists’ addresses.

Publication: 17 June 2013
MS 339-105