Mapping, petrology, and paleocurrent investigations by the speaker and students provide new evidence of sedimentation in a continuously active orogenic belt in southwestern Oregon. Formational units have been traced into California, demonstrating that at least the northern part of the "Franciscan terrane" is divisible. Intensely sheared, northerly trending zones up to 3 miles wide have been traced from California for 100 miles north along the Oregon coast. They pass offshore beneath the seismically active northeast Pacific Basin. Paleogeology shows that these were superimposed upon arcuate Klamath Province fold trends from late Mesozoic to the present.

Extrusion of Jurassic rhyolitic to basaltic marine pillow lava and pyroclastics accompanied deposition of graded and non-graded arkosic wacke, mudstone and bedded chert (Dothan and Rogue? Formations). Associated local conglomerates contain granitic boulders, evidencing hitherto unrecognized "pre-Nevadan" granites. Laminated quartz arenite and argillite intruded by diorite contain Late Jurassic? Foraminifera (Galice Formation). Over large areas these units all have been metamorphosed to form the Colebrook Schist. Thus Late Jurassic orogeny is recorded by deformation, metamorphism, and ultramafic and dioritic plutons. Latest Jurassic and Early Cretaceous rocks contain excellently graded volcanic wackes, mudstone, and thick chert-volcanic conglomerates (Myrtle Group). Diorite, serpentine and schist clasts together with overlap relationships provide sensitive indicators of diastrophic pulses. Volcanism ceased during Cretaceous.

Later orogeny is recorded by severe deformation (but lack of metamorphism) of the Myrtle Group, emplacement of batholiths inland in the eastern Klamath Province, and unconformable overlap by shallow marine Late Cretaceous (Campanian) quartz arenites, quartz wackes, and mudstone. Major shear zones were developed at least by mid-Cretaceous and have been reactivated intermittently since. Post-Cretaceous warping and erosion recurred prior to widespread Eocene transgression, renewed volcanism, and deposition of graded volcanic wackes cross-stratified volcanic arenites, and coal. Regression commenced in Late Eocene. Later Cenozoic movements along the major faults apparently formed the north-trending Coos synclinorium and were related to formation of north-trending Cascade volcanoes and plut ns and to widespread faulting in eastern Oregon and Nevada.

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