Abstract

Combined biostratigraphic, chronostratigraphic, and geochronometric studies of the Rogue and Galice Formations (Rogue Valley subterrane, southwestern Oregon) indicate that the Oxfordian-Kimmeridgian boundary should be placed at 154 ±1.5 Ma rather than at 156 ±6 Ma as advocated in the Decade of North American Geology 1983 geologic time scale. In the Smith River subterrane (northwestern California, southwestern Oregon), well-preserved Radiolaria were recovered not only from strata overlying the Josephine ophiolite, but also from within the volcanic member of the ophiolite. U/Pb geochronometric data constrain the age of the Mirifusus first-occurrence event to after 162 ±1 Ma and to being 157 ±1.5 Ma or slightly older. Radiolarian faunal data indicate that the Josephine ophiolite originated at Central Tethyan paleolatitudes during the latest Callovian (162 Ma) and was carried northward to Northern Tethyan and Southern Boreal paleolatitudes during the Oxfordian.

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