Early to middle Eocene history of the Arctic Ocean from Nd-Sr isotopes in fossil fish debris, Lomonosov Ridge

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doi: 10.1029/2008PA001685
Author(s): Gleason, J. D.; Thomas, D. J.; Moore, T. C., Jr.; Blum, J. D.; Owen, R. M.; Haley, B. A.
Author Affiliation(s): Primary:
University of Michigan, Department of Geological Sciences, Ann Arbor, MI, United States
Other:
Texas A&M University, United States
University of Kiel, Federal Republic of Germany
Volume Title: Paleoceanography
Source: Paleoceanography, 24(2). Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. 105 refs.; illus., incl. 2 tables, sketch map
Summary: Strontium and neodymium radiogenic isotope ratios in early to middle Eocene fossil fish debris (ichthyoliths) from Lomonosov Ridge (Integrated Ocean Drilling Program Expedition 302) help constrain water mass compositions in the Eocene Arctic Ocean between ∼55 and ∼45 Ma. The inferred paleodepositional setting was a shallow, offshore marine to marginal marine environment with limited connections to surrounding ocean basins. The new data demonstrate that sources of Nd and Sr in fish debris were distinct from each other, consistent with a salinity-stratified water column above Lomonosov Ridge in the Eocene. The 87Sr/86Sr values of ichthyoliths (0.7079-0.7087) are more radiogenic than Eocene seawater, requiring brackish to fresh water conditions in the environment where fish metabolized Sr. The 87Sr/86Sr variations probably record changes in the overall balance of river Sr flux to the Eocene Arctic Ocean between ∼55 and ∼45 Ma and are used here to reconstruct surface water salinity values. The εNd values of ichthyoliths vary between -5.7 and -7.8 compatible with periodic (or intermittent) supply of Nd to Eocene Arctic intermediate water (AIW) from adjacent seas. Although the Norwegian-Greenland Sea and North Atlantic Ocean were the most likely sources of Eocene AIW Nd, input from the Tethys Sea (via the Turgay Strait in early Eocene time) and the North Pacific Ocean (via a proto-Bering Strait) also contributed.
Year of Publication: 2009
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Alkaline earth metals; Arctic Coring EXpedition; Arctic Ocean; Bones; Cenozoic; Chordata; Eocene; Expedition 302; Integrated Ocean Drilling Program; Isotope ratios; Isotopes; Lomonosov Ridge; Marine environment; Metals; Nd-144/Nd-143; Neodymium; Paleo-oceanography; Paleoenvironment; Paleogene; Pisces; Rare earths; SEM data; Sr-87/Sr-86; Stable isotopes; Strontium; Tertiary; Vertebrata
Coordinates: N875100 N875600 E1393300 E1361000
Record ID: 2010081648
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