Therese Schneck
Civil Engineer CEO International Ordovician&Petroleum Services
http://www.internationalordovicianandpetroleumservices.com

Regards.

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 107, NO. B6, 2114,
doi:10.1029/2001JB000491, 2002

Geomagnetic excursions and paleointensities in the Matuyama Chron
at Ocean Drilling Program Sites 983 and 984 (Iceland Basin)

J. E. T. Channell

Department of Geological Sciences, University of Florida,
Gainesville, Florida, USA




A. Mazaud

Laboratoire des Sciences du Climat et de l'Environnement,
Gif-sur-Yvette, France




P. Sullivan

Department of Geological Sciences, University of Florida,
Gainesville, Florida, USA




S. Turner

Department of Geological Sciences, University of Florida,
Gainesville, Florida, USA




M. E. Raymo

Department of Earth Sciences, Boston University, Boston,
Massachusetts, USA




Abstract
We report natural remanent magnetization (NRM) directions and
geomagnetic paleointensity proxies for part of the Matuyama Chron
(0.9¨C2.2 Ma interval) from two sites located on sediment drifts in
the Iceland Basin. At Ocean Drilling Program Sites 983 and 984,
mean sedimentation rates in the late Matuyama Chron are 15.9 and
11.5 cm kyr−1, respectively. For the older part of the record
(>1.2 Ma), oxygen isotope data are too sparse to provide the sole
basis for age model construction. The resemblance of the volume
susceptibility record and a reference ¦Ä18O record led us to match
the two records to derive the age models. This match, based on Site
983/984 susceptibility, is consistent with available Site 983/984
benthic ¦Ä18O data. Paleointensity proxies were derived from the
slope of the NRM versus anhysteretic remanent magnetization plot
for alternating field demagnetization in the 30¨C60 mT peak field
range. Paleointensity lows correspond to polarity reversals at the
limits of the Jaramillo, Olduvai, Cobb Mountain, and R¨¦union
Subchrons and to seven excursions in NRM component directions.
Magnetic excursions (defined here by virtual geomagnetic polar
latitudes crossing the virtual geomagnetic equator) are observed at
932, 1048, 1115, 1190¨C1215 (Cobb Mountain Subchron), 1255,
1472¨C1480, 1567¨C1575 (Gilsa Subchron), and 1977 ka. The results
indicate that geomagnetic directional excursions, associated with
paleointensity minima, are a characteristic of the Matuyama Chron
and probably of polarity chrons in general.

Published 13 June 2002.

Index Terms: 1520 Geomagnetism and Paleomagnetism:
Magnetostratigraphy; 1513 Geomagnetism and Paleomagnetism:
Geomagnetic excursions; 1535 Geomagnetism and Paleomagnetism:
Reversals (process, timescale, magnetostratigraphy); 1521
Geomagnetism and Paleomagnetism: Paleointensity.