Khelifi, Nabil et al. (2008): Pliocene changes in Mediterranean outflow water before and after Gibraltar

DSDP 80 548

Khelifi, Nabil
University of Kiel, Kiel, Germany

Sarnthein, Michael

Frank, Martin

Weinelt, Mara

Andersen, Nils

Garbe-Schoenberg, Dieter

Pliocene changes in Mediterranean outflow water before and after Gibraltar
In: Anonymous, 33rd international geological congress; abstracts
[International Geological Congress], [location varies], International
Pliocene changes in the Mediterranean Outflow (3.6 - 2.5 Ma) were studied at East Atlantic DSDP Site 548 which lies today within the depth range of modern Mediterranean Outflow Water (MOW; 1250 m w.d.). This site provided a largely continuous benthic record of bottom water variability with millennial-scale resolution from 3.68 Ma (MIS Gi01) to 2.56 Ma (MIS 101; tuned to age scale LR04). We assume that MOW spilled this Site 548 almost continuously over the whole interval studied, since Nd isotopes remained constant at epsilon = -10.3+ or -0.3 to -9.5+ or -0.3, a range characteristic of Mediterranean waters. Mg/Ca-based bottom water temperatures show a major increase near 3.46 to 3.38 Ma - for reasons yet unknown - from an average of 6 degrees -8 degrees C up to a plateau of 8 degrees -11.5 degrees C, which lasted until 2.95 Ma (MIS G17). Subsequently, bottom water temperatures displayed a unique short-lasting drop down to 3 degrees C at MIS G10 (2.82 Ma), a drop coeval with the final closure of Central American Seaways (CAS) and the onset of major Northern Hemisphere Glaciation (NHG; Bartoli et al., 2005). After MIS G10 bottom water temperatures returned to 6 degrees -8 degrees C, a level characteristic of modern MOW and being traced until 2.56 Ma (MIS 101). Since ice-volume corrected benthic delta 18O values do not reflect any of these immense changes, the long-term temperature rise of 3 degrees -4 degrees C also implies a major increase of bottom water salinity by 1.5 to 2.0 p.s.u. Accordingly, the plateau reflects intensified advection of MOW and salt discharge to the northern North Atlantic, that may have strengthened North Atlantic THC and thus preconditioned the onset of NHG. Only after 2.95 Ma, during the final closure of the CAS, the high Mediterranean salt input was replaced by salt discharge from the Caribbean. Since this time epibenthic delta 13C values indicate slightly improved ventilation of MOW, that came close to the modern-to-Late Pleistocene level. In contrast to the outlined high level of temperature and salinity MOW ventilation was somewhat reduced prior to 3 Ma, suggesting mid-Pliocene Mediterranean climates and in particular, a regime of continental wetness that was significantly different from today. - The multiproxy records DSDP Site 548 are supplemented by Pliocene paleoceanographic records from the Mediterranean source region (ODP 978) to study Pliocene variations in the initial composition of Mediterranean Intermediate Water prior to its mixing with North Atlantic intermediate water masses.
Coverage:Geographic coordinates:
West:-12.0951East: 42.0000

Stratigraphy; alkaline earth metals; Atlantic Ocean; bottom water; calcium; Cenozoic; Deep Sea Drilling Project; DSDP Site 548; Europe; Gibraltar; glaciation; Goban Spur; Iberian Peninsula; IPOD; isotopes; Leg 80; magnesium; Mediterranean Intermediate Water; Mediterranean Outflow Water; Mediterranean Sea; metals; Mg/Ca; neodymium; Neogene; North Atlantic; paleo-oceanography; paleoclimatology; paleosalinity; Pliocene; rare earths; Southern Europe; temperature; Tertiary; ventilation;