Paleointensity of the geomagnetic field in the Late Cretaceous and earliest Paleogene obtained from drill cores of the Louisville Seamount trail

Online Access: Get full text
doi: 10.1002/2014GC005298
Author(s): Yamazaki, Toshitsugu; Yamamoto, Yuhji
Author Affiliation(s): Primary:
Geological Survey of Japan, Tsukuba, Japan
Kochi University, Japan
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 15(6), p.2454-2466. Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English; illus., incl. 1 table, sketch map
Summary: Information on the strength of the geomagnetic field is important for understanding the behavior of the geodynamo. Polarity reversal frequency increases toward the late Cenozoic since the end of the Cretaceous Normal Superchron. Accumulating reliable paleointensity data in this time interval is still desired for elucidating the possibility of a link between reversal frequency and paleointensity. We conducted a paleointensity study on 288 samples from four seamounts from ∼74 to ∼50 Ma in age that constitutes the Louisville seamount trail. Based on thermomagnetic curves and scanning electron microscopy, we first excluded 134 samples that showed evidence for low-temperature oxidation. We then applied the Tsunakawa-Shaw method with low-temperature demagnetization and double heating after rejecting some samples that do not preserve stable primary remanence, and 52 successful results were obtained. An average virtual axial dipole moment (VADM) of 3.75 ± 1.52 (1022 Am2) was obtained at Site U1372 on Canopus seamount (∼74 Ma) based on 16 independent measurements. Sites U1373 and U1374 on Rigil seamount (∼70 Ma) yielded a mean of 3.79 ± 1.40 (n = 16), and Site U1376 on Burton seamount (∼65 Ma) yielded a mean of 3.70 ± 1.37 (n = 8). These VADMs are similar to the long-term average of the last 200 Myr by Tauxe et al. (2013) and the mean of the last 5 Myr by Yamamoto and Tsunakawa (2005). The volcanic sequence drilled at Site U1372 probably belongs to Chron C33n of 5.59 Myr long, whereas others belong to shorter chrons. Our results support no discernible relationship between polarity length and paleointensity. Abstract Copyright (2014), American Geophysical Union. All Rights Reserved.
Year of Publication: 2014
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 17 Geophysics, General; Boreholes; Burton Seamount; Cenozoic; Cores; Cretaceous; Demagnetization; Dynamos; East Pacific; Electron microscopy data; Expedition 330; IODP Site U1372; IODP Site U1373; IODP Site U1374; Integrated Ocean Drilling Program; Louisville Ridge; Lower Paleocene; Magnetic field; Magnetic intensity; Magnetic properties; Magnetization; Mesozoic; Ocean floors; Pacific Ocean; Paleocene; Paleogene; Paleomagnetism; Remanent magnetization; Reversals; SEM data; Seamounts; South Pacific; Southeast Pacific; Tertiary; Thermoremanent magnetization; Upper Cretaceous
Coordinates: S400000 S200000 W1650000 W1800000
Record ID: 2016043641
Copyright Information: GeoRef, Copyright 2019 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