About 225 lava flows and ash-flow tuffs of the Deschutes Formation (DF) were mapped at Green Ridge. The units fill east-trending paleovalleys which "sky-out" westward and dip east; the eastward dip of the units decreases
as they are traced eastward. The source of the units was west of Green Ridge...
Four formations of the Cretaceous Nanaimo Group crop out on Galiano Island and on Parker and Gossip Islands, nearby. These formations are: early Campanian Geoffrey Formation which encloses a tongue of the Northumberland Formation; early Campanian to late Maestrichtian Spray Formation; and Maestrichtian Gabriola Formation. The stratigraphic succession has a...
Two ash-flow tuff units of the late Miocene-early Pliocene Deschute Formation in central Oregon were studied in detail because of the widespread distribution, diverse compositions, and stratigraphic importance.
The Lower Bridge tuff is a double-flow simple
cooling unit that is poorly welded. The upper flow grades from rhyolite in the...
A sequence of volcanic, volcaniclastic, and epiclastic deposits from Oligocene to Recent age are exposed in the region from Lake
Simtustus to Madras in central Oregon. The epiclastic sediments of the Oligocene John Day Formation are unconformably overlain by two flows of the middle Miocene Columbia River Basalt Group. The...
The Peck Mountain area is located in west-central Idaho just 15 miles east of the Oregon-Idaho border. It is tectonically located within the "Columbia Arc" of the Nevadan oroaenic belt. The Seven Devils Volcanics, Permian to Traissic in age, are the oldest rocks in the area. They are composed of...
The Whitewater River area is located directly east of Mt. Jefferson in the Cascades of central Oregon. Approximately 90 mi2 (230 km2) were mapped (scale 1/24,000) and four new K-Ar ages and 151 major element analyses were obtained in a study of the stratigraphic
and magmatic transition from the Miocene...
The Mitchell inlier in north-central Oregon contains the largest exposure of Cretaceous marine sedimentary rocks in this region. Nearly 9,000 ft of Albian-Cenamanian rocks are exposed along the flanks of the Mitchell anticline. The Cretaceous section rests unconformably overlain by Tertiary volcanic rocks. The Cretaceous rocks have previously been divided...
Geologic mapping of the Longview-Kelso area and the measurement and description of a composite 650-meter thick stratigraphic section of the Cowlitz Formation (Tc) in Coal Creek using bio-, magneto-, litho-, and sequence stratigraphy reveals a complex interplay of Cowlitz micaceous, lithic arkosic shelf to tidal/estuarine to delta
plain facies associations,...
The Bend pumice and Tumalo tuff are products of a plinian eruption which occurred sometime between 0.89 and 2.6 m.y. The Bend pumice is a poorly consolidated, air-fall vitric lapilli tuff, which overlies a zone of reworked tephra. Perlitic obsidian in the reworked zone probably represents the remains of a...
About 9600 nautical miles of marine gravity, magnetic, and bathymetric data were collected by Oregon State University during the cruise Yucatan'85 in the north and eastern margins of the Yucatan Peninsula, using a research vessel of the Mexican Navy, the Altair. A compilation of Yucatan' 85 marine data and marine...
The Tumalo quadrangle lies approximately 30 kilometers behind the Cascade volcanic arc and marks the southernmost extent of continuously exposed Deschutes Formation rocks. Deschutes Formation rocks in the
Tumalo quadrangle include late Miocene volcaniclastic sedimentary rocks, ignimbrites and lapillistones, and late Miocene to early
Pliocene basalts and basaltic andesites. Volcaniclastic...
A thick sequence of intercalated andesite and basalt flows, tuffs, and volcanic sediments crop out in the Fly Creek Quadrangle and the north half of the Round Butte Dam Quadrangle. This sequence was deposited in the ancestral Deschutes River Valley along the east flank of the Cascade Range during the...
The thesis area is located in north-central Oregon approximately 20 km west of the town of Mitchell. The rocks exposed in the area belong to the Clarno Formation. This study supports the informal reclassification of the Clarno to Group status, composed of an Upper and Lower Clarno Formation. An angular...
The mapped area is part of the middle Deschutes Basin of central Oregon, which lies in the northwestern corner of the High Lava Plains physiographic province, between the Cascade and Ochoco Mountains. It is underlain by Cenozoic lavas, tuffs and sediments of continental origin. The oldest rocks in the sequence...
During Early and Middle Devonian time, the main part of the Death Valley area was characterized by shallow marine shelf position. In the extreme western part, deposition took place in carbonate slope environments. Early and Middle Devonian eastern platform dolomites, represented by uppermost Hidden Valley Dolomite and lower Lost Burro...