Foraminifer isotope study of the Pleistocene Labrador Sea, northwest North Atlantic (IODP Sites 1302/03 and 1305), with emphasis on paleoceanographical differences between its "inner" and "outer" basins

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doi: 10.1016/j.margeo.2010.11.001
Author(s): Hillaire-Marcel, Claude; de Vernal, Anne; McKay, Jennifer
Author Affiliation(s): Primary:
Université du Québec à Montreal, GEOTOP, Montreal, QC, Canada
Volume Title: Marine Geology
Source: Marine Geology, 279(1-4), p.188-198. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0025-3227 CODEN: MAGEA6
Note: In English. 51 refs.; illus., incl. 1 table, sketch map
Summary: Cores raised during IODP Expedition 303 off southern Greenland (Eirik Ridge site 1305) and off the Labrador Coast (Orphan Knoll site 1302/1303) were analyzed to establish an isotope stratigraphy, respectively for the "inner" and "outer" basins of the Labrador Sea (LS). These isotopic data also provide information on the Atlantic Meridional Overturning Circulation (AMOC), notably with regard to the intensity of the Western Boundary Under Current (WBUC), which is tightly controlled by the production of Denmark Strait Overflow Water (DSOW), and the production of Labrador Sea Water (LSW) in the inner basin through winter cooling and convection. The upper 184m of sediment at Eirik Ridge spans marine isotope stages (MIS) 32 to 1. At this site, two distinct regimes are observed: prior to MIS 20, the isotopic record resembles that of the open North Atlantic records of the interval, whereas a more site-specific pattern is observed afterwards. This later pattern was characterized by i) high DSOW production rates and strong WBUC during interglacial stages, as indicated by sedimentation rates, ii) large amplitude δ18O-shifts from glacial stages to interglacial stages (> 2.5ppm) and iii) an overall range of δ18O-values significantly more positive than before. At Orphan Knoll, the 105m record spans approximately 800ka and provides direct information on linkages between the northeastern sector of the Laurentide Ice Sheet and the North Atlantic. At this site, a shift towards larger amplitude glacial/interglacial ranges of δ18O-values occurred after MIS 13, although isotopic records bear a typical North Atlantic signature, particularly during MIS 5, in contradiction to those of Eirik Ridge, where substages 5a to 5c are barely recognized. Closer examination of δ18O-records in planktic and benthic foraminifera demonstrates the presence of distinct deep-water masses in the inner vs. outer LS basins during MIS 11 and more particularly MIS 5e. Data confirm that the modern AMOC, with LSW formation, seems mostly exclusive to the present interglacial, and also suggest some specificity of each interglacial with respect to the production rate of DSOW and the AMOC, in general. Abstract Copyright (2011) Elsevier, B.V.
Year of Publication: 2011
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 24 Surficial Geology, Quaternary Geology; Atlantic Ocean; Boreholes; C-13/C-12; Carbon; Cenozoic; Chemostratigraphy; Chronostratigraphy; Cores; Expedition 303; Expeditions 303/306; Foraminifera; Glacial environment; Glacial geology; IODP Site U1302; IODP Site U1303; IODP Site U1305; Ice sheets; Integrated Ocean Drilling Program; Interglacial environment; Invertebrata; Isotope ratios; Isotopes; Labrador Sea; Laurentide ice sheet; Lithostratigraphy; MIS 5; Marine sediments; Microfossils; North Atlantic; Northwest Atlantic; O-18/O-16; Oxygen; Paleo-oceanography; Paleoclimatology; Pleistocene; Protista; Quaternary; Sedimentation; Sedimentation rates; Sediments; Stable isotopes
Coordinates: N501000 N501000 W0453800 W0453800
N501200 N501200 W0454100 W0454100
N572800 N572900 W0483200 W0483200
Record ID: 2011026391
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands