HR: 0830h
AN: GP41C-0054    [PDF]
TI: Paleomagnetism of the Upper Cretaceous Units of the Gold Beach Terrane, Southwest Coastal Oregon
AU: * Liner, N C
EM: sleepymonk@yahoo.com
AF: Western Washington University, 516 high st. ms 9080, bellingham, wa 98225 United States
AU: housen, b
EM: bhousen@cc.wwu.edu
AF: Western Washington University, 516 high st. ms 9080, bellingham, wa 98225 United States
AB: Latitudinal displacement of the Gold Beach terrane, southwest coastal Oregon, is enigmatic. Gold Beach terrane is composed of Jurassic vocaniclastic sandstone and Upper Cretaceous marine sandstone. Previously published paleomagnetic evidence using the Jurassic Otter Point formation indicates 1200 to 1400 km. of post-Jurassic northward displacement along the Cordilleran margin (Blake, et al. 1985). The Upper Cretaceous formations are the subjects of a new paleomagnetic study intended to quantify the amount of displacement, age of magnetization and effects of compaction. Initial results indicate well-defined, consistent directions in some samples, and a positive intra-formational conglomerate test indicating an ancient magnetization. Using a combination of rock magnetic tests of partial anhysteretic remanence and the Lowrie (1990) method has shown a combination of coarse to medium-grained pyrrhotite and magnetite present in several samples. Pretreatment by cooling in liquid nitrogen significantly reduced the magnitude of NRM, consistent with presence of coarse-grained magnetite. It may be possible to show that pyrrhotite carries an ancient magnetization if vectors isolated between 160 to 320 degrees can pass a conglomerate test. If both pyrrhotite and magnetite carry a definable set of ancient directions, a detailed comparison between inclinations of both authigenic and presumably detrital remanence carriers can be made.
DE: 1525 Paleomagnetism applied to tectonics (regional, global)
DE: 1527 Paleomagnetism applied to geologic processes
DE: 1535 Reversals (process, timescale, magnetostratigraphy)
DE: 1594 Instruments and techniques
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2003 Fall Meeting