Magnetic stratigraphy and tectonic rotation of the Eocene-Oligocene Keasey Formation, northwest Oregon
作者： Donald R. Prothero , Karina G. Hankins
DOI: 10.1029/2000JB900063
关键词: Basement (geology) 、 Geology 、 Forearc 、 Cenozoic 、 Paleontology 、 Foraminifera 、 Phanerozoic 、 Stage (stratigraphy) 、 Magnetostratigraphy 、 Paleogene 、 Earth-Surface Processes 、 Ecology (disciplines) 、 Earth and Planetary Sciences (miscellaneous) 、 Space and Planetary Science 、 Palaeontology 、 Forestry 、 Aquatic science 、 Atmospheric Science 、 Soil science 、 Geochemistry and Petrology 、 Geophysics 、 Oceanography 、 Water Science and Technology
摘要: The upper Eocene-lower Oligocene Keasey Formation in northwestern Oregon consists of ∼700 m deep marine forearc basin sediments exposed stream beds and roadcuts. abundant molluscs this unit were the basis for Stage Weaver et al. [1944] timescale, but precise age fauna formation have long been controversial. Analysis over 130 magnetic samples from five sections yielded a stable remanence held mainly magnetite which passed reversal test. On calibration by benthic foraminifera is correlative with Chrons C15r-C12r (35.0-33.0 Ma), so spans latest Eocene early Oligocene. directions suggest tectonic rotation 73.7° ± 4.7°, consistent nearest volcanic basement rock reported Wells Coe [1985].
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