HR: 11:50h
AN: GP42A-07    [Abstracts]
TI: The paleointensity of single silicate crystals from the Southern Volcanics of the Chatham Islands: What is the behavior of Earth's magnetic field leaving a superchron state?
AU: * Sail, A B
EM: asail@mail.rochester.edu
AF: University of Rochester, Department of Earth and Environmental Sciences, 227 Hutchison Hall, Rochester, NY 14627, United States
AU: Tarduno, J A
EM: john@earth.rochester.edu
AF: University of Rochester, Department of Earth and Environmental Sciences, 227 Hutchison Hall, Rochester, NY 14627, United States
AU: Cottrell, R D
AF: University of Rochester, Department of Earth and Environmental Sciences, 227 Hutchison Hall, Rochester, NY 14627, United States
AU: Sutherland, R
EM: r.sutherland@gns.cri.nz
AF: Institute of Geological & Nuclear Sciences, PO Box 30-368, Lower Hutt, Wellington, 6315, New Zealand
AU: Campbell, H
EM: h.campbell@gns.cri.nz
AF: Institute of Geological & Nuclear Sciences, PO Box 30-368, Lower Hutt, Wellington, 6315, New Zealand
AB: While the strength of Earth's magnetic field during the Cretaceous Normal Polarity Superchron has been the subject of several recent (and on-going) studies, very little is known about the behavior of the magnetic field during the transition from a superchron to a mixed polarity state. To examine this issue, a new paleointensity study has been conducted using plagioclase crystals from the Late Cretaceous Southern Volcanics of the Chatham Islands, New Zealand. Plagioclase crystals are sought as paleointensity recorders because prior studies have demonstrated that they can contain minute (50 to 250 nm) magnetic inclusions with ideal magnetic properties. Such crystals have also been show to alter less than bulk lava samples during Thellier paleointensity experiments. Furthermore the silicate host can shelter the magnetic inclusions from in situ alteration that commonly occurs on geologic time scales, compromising the paleointensity fidelity of whole rock lava samples. Magnetic hysteresis data, collected using a Princeton Measurements Alternating Gradient Force Magnetometer and P1 probes, confirm that plagioclase crystals from lavas and dikes of the Southern Volcanics contain magnetic inclusions that are near single domain in character. Thus, the crystals are well-suited for paleointensity analysis. Magnetic hysteresis and first order reversal curves (FORCs) will be presented to examine potential differences in the magnetic inclusions between individual lavas and dikes. In addition, results derived from Thellier-Coe paleointensity analyses of single plagioclase crystals separated from select units of the Southern Volcanics will be presented and compared with values from other studies.
DE: 1521 Paleointensity
DE: 1535 Reversals: process, timescale, magnetostratigraphy
DE: 1540 Rock and mineral magnetism
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Fall Meeting