Robustness of fossil fish teeth for seawater neodymium isotope reconstructions under variable redox conditions in an ancient shallow marine setting

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doi: 10.1002/2015GC006218
Author(s): Huck, Claire E.; van de Flierdt, Tina; Jiménez-Espejo, Francisco J.; Bohaty, Steven M.; Röhl, Ursula; Hammond, Samantha J.
Author Affiliation(s): Primary:
Imperial College London, Department of Earth Science and Engineering, London, United Kingdom
University of Southampton, United Kingdom
Japan Agency for Marine-Earth Science and Technology, Japan
University of Bremen, Germany
Open University, United Kingdom
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 17(3), p.679-698. Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. 111 refs.; illus., incl. 2 tables
Summary: Fossil fish teeth from pelagic open ocean settings are considered a robust archive for preserving the neodymium (Nd) isotopic composition of ancient seawater. However, using fossil fish teeth as an archive to reconstruct seawater Nd isotopic compositions in different sedimentary redox environments and in terrigenous-dominated, shallow marine settings is less proven. To address these uncertainties, fish tooth and sediment samples from a middle Eocene section deposited proximal to the East Antarctic margin at Integrated Ocean Drilling Program Site U1356 were analyzed for major and trace element geochemistry, and Nd isotopes. Major and trace element analyses of the sediments reveal changing redox conditions throughout deposition in a shallow marine environment. However, variations in the Nd isotopic composition and rare earth element (REE) patterns of the associated fish teeth do not correspond to redox changes in the sediments. REE patterns in fish teeth at Site U1356 carry a typical mid-REE-enriched signature. However, a consistently positive Ce anomaly marks a deviation from a pure authigenic origin of REEs to the fish tooth. Neodymium isotopic compositions of cleaned and uncleaned fish teeth fall between modern seawater and local sediments and hence could be authigenic in nature, but could also be influenced by sedimentary fluxes. We conclude that the fossil fish tooth Nd isotope proxy is not sensitive to moderate changes in pore water oxygenation. However, combined studies on sediments, pore waters, fish teeth, and seawater are needed to fully understand processes driving the reconstructed signature from shallow marine sections in proximity to continental sources. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.
Year of Publication: 2016
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Cenozoic; Chordata; Eh; Eocene; Expedition 318; IODP Site U1356; Integrated Ocean Drilling Program; Isotope ratios; Isotopes; Marine environment; Metals; Middle Eocene; Nd-144/Nd-143; Neodymium; Paleo-oceanography; Paleoenvironment; Paleogene; Pisces; Rare earths; Reconstruction; Sea water; Shallow-water environment; Southern Ocean; Stable isotopes; Teeth; Tertiary; Vertebrata
Coordinates: S631837 S631837 E1355956 E1355956
Record ID: 2017055352
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