Permian and Triassic Rocks of Northeastern Oregon

Bostwick, David; Koch, George S.

doi:10.1130/0016-7606(1962)73[419:patron]2.0.co;2

Cited by 14 publications

(13 citation statements)

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“…Cordey, -2009, indicating that deep-sea deposition possibly continued into Jurassic time. Both Tethyan and McCloud fusulinids are reported from the Bourne subterrane (Bostwick and Koch, 1962;Bostwick and Nestell, 1965;Nestell, 1983). The presence of McCloud-type fauna in rocks of the Bourne and Greenhorn subterranes implies a paleo geographic tie to an inferred oceanic arc that fringed the continental margin of western North America in Permian time (Miller, 1987).…”

Section: Bourne Subterranementioning

confidence: 92%

Analysis of the Wallowa-Baker terrane boundary: Implications for tectonic accretion in the Blue Mountains province, northeastern Oregon

Schwartz

Snoke

Frost

et al. 2009

Geological Society of America Bulletin

108

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The Baker terrane, exposed in the Blue Mountains province of northeastern Oregon, is a long-lived, ancient (late Paleozoic-early Mesozoic) accretionary complex with an asso ciated forearc. This composite terrane lies between the partially coeval Wallowa and Olds Ferry island-arc terranes. The northern margin of the Baker terrane is a broad zone (>25 km wide) of fault-bounded, imbricated slabs and slices of metaigneous and metasedimentary rocks faulted into chert-argillite mélange of the Elkhorn Ridge Argillite. Metaplutonic rocks within tectonic units in this zone crystallized between 231 and 226 Ma and have low initial 87 Sr/ 86 Sr ratios (0.7033-0.7034) and positive initial ε Nd values (+7.7 to +8.5). In contrast, siliceous argillites from the chert-argillite mélange have initial 87 Sr/ 86 Sr values ranging from 0.7073 to 0.7094 and initial ε Nd values between -4.7 and -7.8. We interpret this broad, imbricate fault zone as a fundamental tectonic boundary that separates the distal, Wallowa island-arc terrane from the Baker accretionary-complex terrane. We propose that this terrane boundary is an example of a broad zone of imbrication made up of slabs and slices of arc crust tectonically mixed within an accretionary complex, providing an on-land, ancient analog to the actualistic arc-arc collisional zone developed along the margins of the Molucca Sea of the central equatorial Indo-Pacifi c region.

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Section: Bourne Subterranementioning

confidence: 92%

Analysis of the Wallowa-Baker terrane boundary: Implications for tectonic accretion in the Blue Mountains province, northeastern Oregon

Schwartz

Snoke

Frost

et al. 2009

Geological Society of America Bulletin

108

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“…Elkhorn Ridge Argillite, which underlies most of the roadless area, consists mostly of a monotonous assemblage of argillite and chert, which originally must have been several thousand feet thick. East of the roadless area the formation has yielded Pennsylvanian and Permian fusulinids and Early to Middle Triassic pentacrinoids, hydrozoans and hexacorals (Bostwick and D. A. Koch, 1962;Bostwick, in Brooks and others, 1976, p. 4), which establish the age of the formation as late Paleozoic and Triassic. Brecciated and retrogressively metamorphosed diorite in the southern and western parts of the roadless area underlie an assemblage of pyroclastic and volcanic rocks.…”

Section: Geologymentioning

confidence: 97%

Mineral resource potential map of the North Fork John Day River Roadless Area, Grant County, Oregon

Evans¹,

Conyac²

1983

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Under the provisions of the Wilderness Act (Public Law 88-577, September 3, 1964), and related acts, the U.S. Geological Survey and the U.S. Bureau of Mines have been conducting mineral surveys of wilderness and primitive areas. Areas officially designated as "wilderness," "wild," or "canoe" when the act was passed were incorporated into the National Wilderness Preservation System, and some of them are presently being studied. The act provided that areas under consideration for wilderness designation should be studied for suitability for incorporation in the Wilderness System. The mineral surveys constitute one aspect of the suitability studies. The act directs that the results of such surveys are to be made available to the public and be submitted to the President and the Congress. This report discusses the results of a mineral survey of the

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“…In contrast, the Baker terrane includes variably metamorphosed ocean-floor fragments-pillowed basalt, radiolarian chert, serpentinite-matrix mélangeand arc-derived rocks of Middle Devonian to Early Jurassic age (e.g., Elkhorn Ridge Argillite and Burnt River Schist; Blome and Nestell, 1991;Schwartz et al, 2010). Early Permian faunas recovered from the Elkhorn Ridge Argillite support an exotic origin (Tethyan, McCloud affinity; e.g., Bostwick and Koch, 1962). Paleomagnetic data from turbidite deposits of the Ochoco basin (Cenomanian Gable Creek Formation; e.g., Wilkinson and Oles, 1971) suggest late Early Cretaceous proximity to the southern Sierra Nevada (~39°N) and vertical-axis clockwise rotation (~37°) with respect to stable North America ( Fig.…”

Section: ■ Regional Setting Blue Mountains Provincementioning

confidence: 99%

Orogenic link ∼41°N–46°N: Collisional mountain building and basin closure in the Cordillera of western North America

et al. 2019

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Polyphase structural mapping and mineral age dating across the Salmon River suture zone in west-central Idaho (Riggins region; ∼45°30′N, ∼117°W–116°W) support a late Mesozoic history of penetrative deformation, dynamothermal metamorphism, and intermittent magmatism in response to right-oblique oceanic-continental plate convergence (Farallon–North America). High-strain linear-planar tectonite fabrics are recorded along an unbroken ∼48 km west-to-east transect extending from the Snake River (Wallowa intra-oceanic arc terrane; eastern Blue Mountains Province) over the northern Seven Devils Mountains into the lower Salmon River Canyon (ancestral North America; western Laurentia). Given the temporally overlapping nature (ca. 145–90 Ma) of east-west contraction in the Sevier fold-and-thrust belt (northern Utah–southeast Idaho–southwest Montana segment), we propose that long-term terrane accretion and margin-parallel northward translation in the Cordilleran hinterland (∼41°N–46°N latitude; modern coordinates) drove mid- to upper-crustal shortening >250 km eastward into the foreland region (∼115°W–113°W). During accretion and translation, the progressive transfer of arc assemblages from subducting (Farallon) to structurally overriding (North American) plates was accommodated by displacement along a shallow westward-dipping basal décollement system underlying the Cordilleran orogen. In this context, large-magnitude horizontal shortening of passive continental margin strata was balanced by the addition of buoyant oceanic crust—late Paleozoic to Mesozoic Blue Mountains Province—to the leading edge of western Laurentia. Consistent with orogenic float modeling (mass conservation, balance, and displacement compatibility), diffuse dextral-transpressional deformation across the accretionary boundary (Salmon River suture: Cordilleran hinterland) was kinematically linked to eastward-propagating structures on the continental interior (Sevier thrust belt; Cordilleran foreland). As an alternative to noncollisional convergent margin orogenesis, we propose a collision-related tectonic origin and contractional evolution for central portions of the Sevier belt. Our timing of terrane accretion supports correlation of the Wallowa terrane with Wrangellia (composite arc/plateau assemblage) and implies diachronous south-to-north suturing and basin closure between Idaho and Alaska.

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Permian and Triassic Rocks of Northeastern Oregon

Cited by 14 publications

References 0 publications

Analysis of the Wallowa-Baker terrane boundary: Implications for tectonic accretion in the Blue Mountains province, northeastern Oregon

Analysis of the Wallowa-Baker terrane boundary: Implications for tectonic accretion in the Blue Mountains province, northeastern Oregon

Mineral resource potential map of the North Fork John Day River Roadless Area, Grant County, Oregon

Orogenic link ∼41°N–46°N: Collisional mountain building and basin closure in the Cordillera of western North America

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