Pliocene anisotropy of magnetic susceptibility (AMS) and diatom stratigraphy from the Wilkes Land margin

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Author(s): Sugisaki, Saiko; Iwai, M.; Tauxe, L.; van de Flierdt, Tina; Cook, C.; Jimenez-Espejo, F.; Passchier, S.; Roehl, U.; González, J.; Escutia, C.
Author Affiliation(s): Primary:
Scripps Institution of Oceanography, La Jolla, CA, United States
Kochi University, Japan
Imperial College London, United Kingdom
CSIC, Instituto Andaluz de Ciencias de la Tierra, Spain
Montclair State University, United States
University of Bremen, Germany
Volume Title: AGU 2012 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2012; American Geophysical Union 2012 fall meeting, San Francisco, CA, Dec. 3-7, 2012. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: During IODP Expedition 318, Sites U1359 and U1361 were drilled on the continental rise offshore the Wilkes subglacial basin to reconstruct the stability of the East Antarctic Ice Sheet (EAIS) during Neogene warm periods, such as the late Miocene and the early Pliocene. As the drilled core has complex story of compaction, erosion (thus hiatuses), and possibly artificial disturbance, identifying these is important for reconstructing paleoenvironments. Anisotropy of magnetic susceptibility (AMS) is sensitive to lithological changes and differential compaction. At site U1359, highly anisotropic layers correspond with lithologic boundaries and hiatuses. In places, it appeared that the degree of anisotropy was controlled by the presence or absence of diatoms. Here we present a detailed study of the relationships between sediment compaction based on AMS fabric and variations in diatom taxa and magnetic mineralogy. There is clear correlation between degree of anisotropy and moisture content; where moisture content is high, the layer is more isotropic, and vice versa. Moreover, the anisotropic layers correspond to layers with abundant fibrous diatom taxa (e.g, Thalassionema nitzschioides). In contrast, the more isotropic layers are dominated by the Pennate diatom taxa (e.g, Rouxia spp.). There are also strong rock magnetic indications for changes in the sources of the magnetic minerals. We will describe our AMS and diatom stratigraphy to 1) characterize sediments compaction with diatom taxa variation and 2) detect the source of magnetic mineralogy throughout Pliocene.
Year of Publication: 2012
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Algae; Antarctica; Biostratigraphy; Cenozoic; Diatoms; Expedition 318; IODP Site U1359; IODP Site U1361; Integrated Ocean Drilling Program; Magnetic properties; Magnetic susceptibility; Microfossils; Neogene; Paleomagnetism; Plantae; Pliocene; Southern Ocean; Tertiary; Wilkes Land
Coordinates: S645415 S645415 E1435738 E1435738
S642434 S642434 E1435312 E1435312
Record ID: 2014061515
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