Benthic Foraminifera-based reconstruction of the first Mediterranean-Atlantic exchange in the early Pliocene Gulf of Cadiz

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doi: 10.1016/j.palaeo.2017.02.009
Author(s): Garcia-Gallardo, Angela; Grunert, Patrick; Van der Schee, Marlies; Sierro, Francisco J.; Jiménez-Espejo, Francisco J.; Alvarez Zarikian, Carlos A.; Piller, Werner E.
Author Affiliation(s): Primary:
University of Graz, Institute of Earth Sciences, Graz, Austria
University of Salamanca, Spain
Japan Agency for Marine-Earth Science and Technology, Japan
Texas A&M University, United States
Volume Title: Palaeogeography, Palaeoclimatology, Palaeoecology
Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Vol.472, p.93-107. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0031-0182 CODEN: PPPYAB
Note: In English. 97 refs.; illus., incl. 1 table, sketch map
Summary: Upper Miocene to lower Pliocene sediment cores from Integrated Ocean Drilling Program (IODP) Hole U1387C (IODP Expedition 339) have been studied. The main goal of this study is to reconstruct initial Mediterranean-Atlantic water exchange after the opening of the Gibraltar Strait in the early Pliocene. Benthic foraminiferal assemblages are the focus of the palaeoceanographic analyses of this work. A distinct faunal turnover indicates a considerable change of the depositional environment at the Miocene/Pliocene boundary. Foraminiferal composition suggests high rates of organic carbon flux and poorly oxygenated sea-floor environment for the basal, late Messinian interval. In contrast, earliest Pliocene assemblages point to periodic advection of warm, better ventilated and likely Mediterranean-sourced waters to the studied site. Parallel periodic changes in Siphonina tubulosa, Globocassidulina subglobosa, and Planulina ariminensis and previously established sedimentological and geochemical records (Zr/Al, δ18O) suggest a rather sluggish Mediterranean Outflow between ∼ 5.3 and 5.2 Ma. Benthic foraminifera, along with sedimentological and geochemical data thus provide the earliest indications of Mediterranean-Atlantic water exchange following the opening of the Gibraltar Strait. Sandy layers become frequent towards the top of the interval. These sediments are rich in shelf foraminifera, reflecting episodes of turbidite deposition possibly caused by tectonic adjustments related to the opening of the Gibraltar Strait. The allochthonous assemblages frequently contain Cibicides lobatulus and C. refulgens, species that have been considered indicators of Mediterranean Outflow Water (MOW) in previous studies. Our results warrant for caution when applying these species as MOW proxy in the fossil record if there is evidence for downslope transport.
Year of Publication: 2017
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Aluminum; Assemblages; Atlantic Ocean; Benthic taxa; Biozones; Cenozoic; Chemical ratios; Expedition 339; Foraminifera; Gulf of Cadiz; IODP Site U1387; Integrated Ocean Drilling Program; Invertebrata; Isotope ratios; Isotopes; Lower Pliocene; Mediterranean Sea; Metals; Microfossils; Miocene; Multivariate analysis; Neogene; North Atlantic; O-18/O-16; Oxygen; Paleo-oceanography; Paleoenvironment; Pliocene; Protista; Stable isotopes; Statistical analysis; Stratigraphic boundary; Tertiary; Upper Miocene; Zirconium; Zr/Al
Coordinates: N364819 N364820 W0074308 W0074308
Record ID: 2017050006
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands