A micropalaeontological perspective on export productivity, oxygenation and temperature in NE Atlantic deep-waters across terminations I and II

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doi: 10.1016/j.gloplacha.2015.06.002
Author(s): Grunert, Patrick; Skinner, Luke; Hodell, David A.; Piller, Werner E.
Author Affiliation(s): Primary:
Rutgers University, Department of Earth and Planetary Sciences, Piscataway, NJ, United States
University of Graz, Austria
University of Cambridge, United Kingdom
Volume Title: Global and Planetary Change
Source: Global and Planetary Change, Vol.131, p.174-191. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0921-8181
Note: In English. Includes appendices. 66 refs.; illus., incl. 2 tables, sketch map
Summary: Census counts of benthic foraminifera were studied from the SW Iberian Margin to reconstruct past changes in deep-water hydrography across Terminations I and II. Detailed benthic faunal data (> 125 µm size-fraction) allow us to evaluate the limitations imposed by taphonomic processes and restricted size-fractions. The comparison of recent (mudline) and fossil assemblages at IODP Site U1385 indicates the quick post-mortem disintegration of shells of astrorhizoid taxa (∼ 80% of the present-day fauna), resulting in impoverished fossil assemblages. While the application of quantitative proxy methods is problematic under these circumstances, the fossil assemblages can still provide a qualitative palaeoenvironmental signal that, while most fully expressed in the 125-212 µm size-fraction, is nonetheless also expressed to some degree in the > 212 µm size-fraction. Variations in the benthic foraminiferal assemblages reveal information about changing organic matter supply, deep-water oxygenation and temperature. MIS 2 is generally characterized by an elevated trophic state and variable oxic conditions, with oxygenation minima culminating in the Younger Dryas (YD) and Heinrich Stadials (HS) 1, 2 and 3. Low oxic conditions coincide with decreased water-temperature and lower benthic δ13C, pointing to the strong influence of a southern sourced water-mass during these periods. HS 1 is the most extreme of these intervals, providing further evidence for a severe temporary reduction or even shutdown of AMOC. With the inception of MIS 1, organic matter supply reduced and a better ventilated deep-water environment bathed by NEADW is established. For Termination II, clear indications of southern-sourced water are limited to the early phase of HS 11. During the latter part of HS 11, the deep-water environment seems to be determined by strongly increased supply of organic matter, potentially explaining the decoupling of benthic δ13C and Mg/Ca records of earlier studies as a phytodetritus effect on the carbon isotope signal. However, the presence of a warm, nutrient-rich and poorly oxygenated water-mass cannot be ruled out. With the inception of interglacial MIS 5e trophic conditions are reduced and ventilation by NEADW increases. Abstract Copyright (2015) Elsevier, B.V.
Year of Publication: 2015
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 10 Paleontology, Invertebrate; 24 Surficial Geology, Quaternary Geology; Assemblages; Atlantic Ocean; Benthic taxa; Cenozoic; Continental margin; Deep-water environment; Europe; Expedition 339; Foraminifera; Granulometry; IODP Site U1385; Iberian Peninsula; Integrated Ocean Drilling Program; Invertebrata; Marine sediments; Microfossils; Morphology; Multivariate analysis; North Atlantic; Northeast Atlantic; Organic compounds; Paleoecology; Paleoenvironment; Paleotemperature; Pleistocene; Protista; Quaternary; Sediments; Shells; Southern Europe; Statistical analysis; Taphonomy; Upper Pleistocene; Upper Weichselian; Weichselian; Younger Dryas
Coordinates: N373417 N373417 W0100719 W0100720
Record ID: 2015093552
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands