Environmental rock-magnetism of Cenozoic red clay in the South Pacific Gyre

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doi: 10.1002/2015GC006062
Author(s): Shimono, Takaya; Yamazaki, Toshitsugu
Author Affiliation(s): Primary:
University of Tsukuba, Graduate School of Life and Environmental Sciences, Tsukuba, Japan
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 17(4), p.1296-1311. Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. 63 refs.; illus.
Summary: Nonfossiliferous red clay can be used for elucidating long-range environmental changes, although such studies were limited so far because of the difficulty in precise age estimation and extremely low sedimentation rates. We conducted an environmental rock-magnetic study of Cenozoic red clay at the Integrated Ocean Drilling Program Site U1365 in the South Pacific Gyre. Magnetostratigraphy could be established only above ∼6 m below the seafloor (mbsf) (∼5 Ma). Below ∼6 mbsf, the ages of the cores were transferred from the published ages of nearby Deep Sea Drilling Project Site 596, which is based mainly on a constant Cobalt flux model, by intercore correlation using magnetic susceptibility and rare earth element content variation patterns. Rock-magnetic analyses including first-order reversal curve diagrams, the ratio of anhysteretic remanent magnetization susceptibility to saturation isothermal remanent magnetization (SIRM), and IRM component analyses revealed that magnetic minerals consist mainly of biogenic magnetite and terrigenous maghemite, and that the proportion of the terrigenous component increased since ∼23 Ma. We consider that the increase reflects a growth of eolian dust flux associated with a northward shift of Australia and the site to an arid region of the middle latitudes. The increase of the terrigenous component accelerated after ∼5 Ma, which may be associated with a further growth of the Antarctic glaciation at that time. This is coeval with the onset of the preservation of magnetostratigraphy, suggesting that the primary remanent magnetization is carried by the terrigenous component. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.
Year of Publication: 2016
Research Program: DSDP Deep Sea Drilling Project
IODP Integrated Ocean Drilling Program
IPOD International Phase of Ocean Drilling
Key Words: 17 Geophysics, General; Cenozoic; Clastic sediments; Clay; DSDP Site 596; Deep Sea Drilling Project; East Pacific; Expedition 329; IODP Site U1365; IPOD; Integrated Ocean Drilling Program; Isothermal remanent magnetization; Leg 91; Maghemite; Magnetic minerals; Magnetic properties; Magnetization; Magnetostratigraphy; Oxides; Pacific Ocean; Paleomagnetism; Remanent magnetization; Sedimentation; Sedimentation rates; Sediments; South Pacific; South Pacific Gyre; Southeast Pacific
Coordinates: S235103 S235103 W1653839 W1653839
Record ID: 2016068950
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