Yamazaki, Toshitsugu and Oda, Hirokuni (2001): A Brunhes-Matuyama polarity transition record from anoxic sediments in the South Atlantic (Ocean Drilling Program Hole 1082C)

Leg/Site/Hole:
ODP 175
ODP 175 1082
Identifier:
2002-016191
georefid

Creator:
Yamazaki, Toshitsugu
Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
author

Oda, Hirokuni
author

Identification:
A Brunhes-Matuyama polarity transition record from anoxic sediments in the South Atlantic (Ocean Drilling Program Hole 1082C)
2001
Earth, Planets and Space
Terra Scientific Publishing Company (TERRAPUB), Tokyo, Japan
53
8
817-827
A paleomagnetic study was performed on Hole 1082C sediment cores taken during the Ocean Drilling Program (ODP) Leg 175 in the South Atlantic in order to obtain a high-resolution Brunhes-Matuyama (B/M) polarity transition record. An average sedimentation rate was as high as 10 cm/kyr. The cores consist of strongly anoxic sediments, which is common for the areas of large material supply. Anoxic sediments, which are geochemically quite active, were considered to be unsuitable for studies on detailed behavior of the geomagnetic field such as polarity transitions. For global site distribution, however, it is necessary to make efforts to retrieve paleomagnetic records from such sediments. A continuous record of directional changes around the transition was obtained from U-channel samples after cleaning by stepwise alternating-field (AF) demagnetization. Consistency of the record was checked using discrete samples taken from the other half of the cores. The coring-induced magnetic overprint of radial-inward direction, which has often been reported from ODP piston-cores, was negligibly small in our cores. Relative paleointensity variation was estimated from remanent intensities of the discrete samples normalized by artificial remanences. Our record shows following features of the B/M transition similar to those already reported by previous studies. A zone of large directional fluctuations with low paleointensities occurs just before the main transition (788 to 795 ka based on the oxygen-isotope stratigraphy), which would correspond to the "Precursor" of Hartl and Tauxe (1996). The virtual geomagnetic poles (VGPs) at the precursor lie along the so-called preferred longitudinal bands over the north-south Americas and Australia-east Asia. After the main transition from the reversed to normal polarity, VGPs stayed in the middle-to-high latitudes over the North America with an intermediate paleointensity for about 5 kyrs, and then moved in the vicinity of the North Pole with full recovery of intensity. Such behavior was reported by Oda et al. (2000). These similarities suggest that the anoxic sediments at Site 1082 could record the behavior of the geomagnetic field rather faithfully, although the remanence may be of chemical origin.
English
Serial
Coverage:Geographic coordinates:
North:-21.0539
West:11.4914East: 11.4914
South:-21.0539

Sedimentary petrology; Geochronology; anaerobic environment; Atlantic Ocean; Brunhes Chron; Cenozoic; geochronology; Leg 175; marine environment; Matuyama Chron; Ocean Drilling Program; ODP Site 1082; paleo-oceanography; paleoenvironment; paleomagnetism; polar wandering; Quaternary; sediments; South Atlantic; upper Cenozoic; upper Quaternary;

.