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

Online Access: Get full text
doi: 10.1002/2014GC005356
Author(s): Bahr, André; Jiménez-Espejo, Francisco J.; Kolasinac, Nada; Grunert, Patrick; Hernández-Molina, F. Javier; Röhl, Ursula; Voelker, Antje H. L.; Escutia, Carlota; Stow, Dorrik A. V.; Hodell, David A.; Alvarez-Zarikian, Carlos A.
Author Affiliation(s): Primary:
University of Frankfurt, Institute of Geosciences, Frankfurt, Germany
Japan Agency for Marine-Earth Science and Technology, Japan
University of Graz, Austria
Royal Holloway University of London, United Kingdom
University of Bremen, Germany
Instituto Portugues do Mar e da Atmosfera, Portugal
Instituto Andaluz de Ciencias de la Tierra, Spain
Heriot-Watt University, United Kingdom
University of Cambridge, United Kingdom
Texas A&M University, United States
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 15(8), p.3145-3160. Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English; illus., incl. 3 tables
Summary: Contourites in the Gulf of Cádiz (GC) preserve a unique archive of Mediterranean Outflow Water (MOW) variability over the past 5.3 Ma. In our study, we investigate the potential of geochemical data obtained by XRF scanning to decipher bottom current processes and paleoclimatic evolution at two different sites drilled during IODP Expedition 339 through contourites in the northern GC: Site U1387, which is bathed by the upper MOW core, and Site U1389, located more proximal to the Strait of Gibraltar. The lack of major downslope transport during the Pleistocene makes both locations ideally suited for our study. The results indicate that the Zr/Al ratio, representing the relative enrichment of heavy minerals (zircon) over less dense alumnosilicates under fast bottom current flow, is the most useful indicator for a semiquantitative assessment of current velocity. Although most elements are biased by current-related processes, the bromine (Br) record, representing organic content, preserves the most pristine climate signal rather independent of grain-size changes. Hence, Br can be used for chronostratigraphy and site-to-site correlation in addition to stable isotope stratigraphy. Based on these findings, we reconstructed MOW variability for Marine Isotope Stages (MIS) 1-5 using the Zr/Al ratio from Site U1387. The results reveal abrupt, millennial-scale variations of MOW strength during Greenland Stadials (GS) and Interstadials (GI) with strong MOW during GS and glacial Terminations and a complex behavior during Heinrich Stadials. Millennial-scale variability persisting during periods of poorly expressed GS/GI cyclicities implies a strong internal oscillation of the Mediterranean/North Atlantic climate system. Abstract Copyright (2014), American Geophysical Union. All Rights Reserved.
Year of Publication: 2014
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 24 Surficial Geology, Quaternary Geology; Aluminosilicates; Aluminum; Arctic region; Atlantic Ocean; Bathymetry; Bottom currents; Cenozoic; Clastic sediments; Contourite; Cores; Currents; Cyclic processes; Expedition 339; Glaciation; Greenland; Gulf of Cadiz; Heavy minerals; IODP Site U1387; IODP Site U1389; Integrated Ocean Drilling Program; Interstadial environment; Isotope ratios; Isotopes; Marine environment; Marine sediments; Mediterranean Outflow; Mediterranean Sea; Metals; Nesosilicates; North Atlantic; O-18/O-16; Ocean currents; Orthosilicates; Oxygen; Paleoclimatology; Pleistocene; Quaternary; Sediments; Silicates; Stable isotopes; Velocity; X-ray analysis; X-ray fluorescence; Zircon; Zircon group; Zirconium
Coordinates: N350000 N370000 W0060000 W0090000
Record ID: 2016027392
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom, Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union