Distinguishing between advection and source changes recorded by Nd isotopes in the NE Atlantic

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doi: 10.1180/minmag.2013.077.5.18
Author(s): Roberts, N. L.; Piotrowski, A. M.
Author Affiliation(s): Primary:
University of Cambridge, Cambridge, United Kingdom
Volume Title: Goldschmidt abstracts 2013
Source: Mineralogical Magazine, 77(5), p.2069; Goldschmidt 2013, Florence, Italy, Aug. 25-30, 2013. Publisher: Mineralogical Society, London, United Kingdom. ISSN: 0026-461X
Note: In English. 8 refs.
Summary: Nd isotopes, measured on authigenic sediment phases, are a powerful tracer of past changes in ocean circulation. Recent method developments have shown that planktonic foraminifera, which have not been chemically cleaned, preserve the Nd isotope signature of bottom water, and thus are an alternative phase to sediment leachates, avoiding possible contamination by volcanic phases. However, interpretation of downcore changes in Nd isotope records, in terms of past changes in water mass proportion, relies on the accurate reconstruction of the endmember composition of water mass source. Records from Fe-Mn crusts and corals from the NW Atlantic, and a sediment leachate record measured on core ODP 980 in the NE Atlantic suggest the Nd isotope composition of the northern source endmember remained constant between the last glacial and the Holocene. However, a recent study comparing sediment leachate and uncleaned foraminifera Nd isotopes from a core close to ODP 980 indicates that sediment leachate data from this region are not reliable, thereby calling into question the invariant nature of the northern source endmember composition. We present Nd isotope records, measured on unclean planktonic foraminifera, from a depth transect of cores in the northern NE Atlantic, which today are bathed by a mixture of overflow waters and Labrador Sea water. Our records sample Nd isotope composition from 1 - 4 km depth, and from 0 -30 ka. We compare our Nd isotope records with previously published benthic δ13C and B/Ca records, measured on the same cores, and used to infer past changes in ocean circulation. We use the observed decoupling between these three proxies to distinguish between endmember source changes in the Nd isotope composition and circulation controlled changes, with implications for interpreting changes in the Nd isotope signatures recorded elsewhere in the N Atlantic.
Year of Publication: 2013
Research Program: ODP Ocean Drilling Program
Key Words: 24 Surficial Geology, Quaternary Geology; Advection; Atlantic Ocean; C-13/C-12; Carbon; Cenozoic; Cores; Ferromanganese crusts; Foraminifera; Holocene; Invertebrata; Isotope ratios; Isotopes; Labrador Sea; Leachate; Leg 162; Marine sediments; Metals; Microfossils; Nd-144/Nd-143; Neodymium; North Atlantic; Northeast Atlantic; ODP Site 980; Ocean Drilling Program; Paleo-oceanography; Planktonic taxa; Pleistocene; Protista; Quaternary; Rare earths; Rockall Bank; Sediments; Stable isotopes
Coordinates: N552906 N552906 W0144208 W0144208
Record ID: 2014023552
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland