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Magnetostratigraphic and Cyclostratigraphic Records from Eocene-Miocene Sediments Cored in the Paleoequatorial Pacific: Initial Results from IODP Expedition 320
University of California, Davis.
Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
2009 (English)Conference paper (Other academic)
Abstract [en]

Sediments from the paleoequatorial Pacific record the paleomagnetic field with high-fidelity and contain cyclic variations in chemical and physical properties that can be astronomically tuned, as has been shown from past Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) cruises, e.g., Legs 85, 138, 198, and 199. In an effort to fill gaps from past coring and to construct complete stratigraphic sections spanning the Cenozoic, Integrated Ocean Drilling Program (IODP) Expeditions 320 and 321 cored sediments along a Pacific Equatorial Age Transect (PEAT) earlier this year. A total of 23 holes at 8 Sites (Sites U1331 through U1338) were cored, recovering 6,141 m of sediment (Preliminary Reports are available at Initial paleomagnetic results from Expedition 320 include measurements at 56,222 intervals along ~2000 split-core sections, as well as detailed progressive alternating field (AF) and thermal demagnetization of over 400 discrete samples (7 cm3 cubes). The cleaned paleomagnetic data were characterized by shallow inclinations, consistent with the sites being near the paleoequator, and by 180° alternations in declination downhole, reflecting magnetic polarity zones. The resulting magnetostratigraphies, which are used to develop initial age models for the drill sites, yield 803 dates ranging from 51.743 Ma (the base of Chron 23n.2n at Site 1331) to the present (Chron C1n; 0 to 0.783 Ma at Site U1335). In addition, 83 short polarity intervals were observed that might correspond to cryptochrons or geomagnetic excursions. We will discuss initial efforts to further resolve the PEAT magnetostratigraphies and to integrate them with bio-, chemo-, and cyclo- stratigraphies from the equatorial Pacific and elsewhere in order to improve and extend astronomical calibration of the geologic timescale.

Place, publisher, year, edition, pages
, Eos Trans. AGU, 90(52), Fall Meet. Suppl.,, Abstract GP22A-04
National Category
Research subject
Geophysics Specialized In Solid Earth
URN: urn:nbn:se:su:diva-34397OAI: diva2:284666
AGU Fall Meeting 2009
Available from: 2010-01-08 Created: 2010-01-08 Last updated: 2012-03-09Bibliographically approved

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