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The geology of part of the Snake River Canyon and adjacent areas in Northeastern Oregon and Western Idaho

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Title The geology of part of the Snake River Canyon and adjacent areas in Northeastern Oregon and Western Idaho
Names Vallier, Tracy L. (Tracy Lowell), 1936- (creator)
Taubeneck, W. H. (advisor)
Date Issued 1967-05-01 (iso8601)
Note Graduation date: 1967
Abstract The mapped area lies between the Wallowa Mountains
of northeastern Oregon and the Seven Devils Mountains of
western Idaho. Part of the Snake River canyon is included.
A composite stratigraphic section includes at least
30,000 feet of strata. Pre- Tertiary and Tertiary strata
are separated by a profound unconformity. Pre -Tertiary
layered rocks are mostly Permian and Triassic volcaniclastic
and volcanic flow rocks. At least four pre -Tertiary
intrusive suites occur. Tertiary rocks are Miocene
and Pliocene plateau basalts. Quaternary glacial materials
and stream deposits locally mantle the older rocks.
Permian ( ?) rocks of the Windy Ridge Formation are
the oldest rocks and consist of 2,000 to 3,000 feet of
keratophyre, quartz keratophyre, and keratophric pyroclastic
rocks. Unconformably ( ?) overlying the Windy
Ridge Formation are 8,000 to 10,000 feet of volcaniclastic
rocks and minor volcanic flow rocks of the Hunsaker Creek Formation of Middle Permian (Leonardian and Wordian) age.
Spilitic flow rocks of the Kleinschmidt Volcanics are
interlayered with and in part overlie the Hunsaker Creek
Formation and comprise a sequence about 2,000 to 3,000
feet thick. The Paleozoic layered rocks were intruded by
the Holbrook - Irondyke intrusives, composed of keratophyre
porphyry, quartz keratophyre porphyry, diabase, and gabbro.
The Paleozoic rocks were deformed by an orogeny between
Middle Permian and Middle Triassic time. Plutonic
rocks (Oxbow Complex) of gabbro, quartz diorite, diorite,
and albite granite were intruded during Early Triassic
(7) time. Movements along the Oxbow -Cuprum shear zone
occurred during and after the intrusions.
Middle Triassic (Ladinian) spilitic flow rocks and
volcaniclastic rocks of the Grassy Ridge Formation overlie
the older rocks with angular unconformity. Thicknesses
are 3,000 to 4,000 feet in the northeast part of the map
area; no rocks of the Grassy Ridge Formation are exposed
in the southwest part. The Imnaha Formation of Late Triassic
(Karnian) age overlies the Permian strata unconformably
near Fish Lake in the western part of the area.
The Doyle Creek Formation of Late Triassic (Karnian) age
conformably overlies the Grassy Ridge Formation in the
Snake River and Imnaha River canyons and may interfinger
with the Imnaha Formation east of Fish Lake. The Doyle Creek Formation ranges in thickness from 3,000 to 5,000
feet and includes two members - the Ashby Creek Conglomerate
and the Piedmont Point Member. The Martin Bridge
Formation, represented by 1,750 feet of Late Triassic
(Norian) limestone, conformably overlies the Doyle Creek
Formation.
At least two intrusive events apparently occurred
during the Jurassic Period. The Jurassic ( ?) intrusives,
were emplaced before regional metamorphism and consist of
hypabyssal dikes and sills of diorite, quartz diorite,
and dacite and andesite porphyries. Subsequently, the
Upper ( ?) Jurassic intrusives were emplaced during a late
stage of regional metamorphism and are represented by
small stocks of gabbro, norite, quartz diorite, and gran -
odiorite porphyry.
A major orogeny during Middle and Late ( ?) Jurassic
time deformed the rocks. Regional metamorphism produced
mineral assemblages characteristic of the greenschist
facies.
Columbia River Basalt, 2,000 to 3,000 feet thick,
erupted from fissures during late Miocene and early Pliocene
time and covered an old erosion surface. Pliocene -
Pleistocene uplift, alpine glaciation, and extensive
stream erosion are responsible for the present topography.
Genre Thesis/Dissertation
Topic Geology -- Oregon -- Snake River Canyon
Identifier http://hdl.handle.net/1957/47345

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