SEDIMENTARY RESPONSE TO EOCENE TECTONIC ROTATION IN WESTERN OREGON (WASHINGTON, PACIFIC NORTHWEST, PETROLOGY).

Persistent Link:
http://hdl.handle.net/10150/187393
Title:
SEDIMENTARY RESPONSE TO EOCENE TECTONIC ROTATION IN WESTERN OREGON (WASHINGTON, PACIFIC NORTHWEST, PETROLOGY).
Author:
HELLER, PAUL LEWIS.
Issue Date:
1983
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Published paleomagnetic studies have shown that the Oregon Coast Range has rotated 60° clockwise since middle Eocene time, probably by pivoting either during collision of a seamount terrane or during an episode of asymmetric extension within western North America. Eocene sedimentary deposits within the Oregon Coast Range basin, in particular the Tyee Formation, document changes in basin evolution that provide geologic constraints for proposed rotation models. The Tyee Formation comprises an arkosic petrofacies which is different from underlying lithic sandstones that were derived from the adjacent Klamath Mountains. Isotopic study of sandstones of the arkosic petrofacies, including Sm-Nd, Rb-Sr, K-Ar, and ¹⁸O analyses, indicate that much of the sandstone was not derived from the Klamath Mountains or nearby Sierra Nevada. The source area most likely included S-type granites of the Idaho Batholith. Lithofacies within the Tyee Formation include a sandy deltaic system to the south, a thin muddy shelf/slope sequence farther north, and a thick basinal sequence of sandy high-density turbidites that grade northward into low-density turbidites. Absence of facies segregation within the turbidite sequence precludes application of classical deep-sea fan depositional models and forms the basis for the delta-fed submarine ramp model introduced here. Delta-fed submarine ramps are short-lived sandy systems that result from rapid rates of progradation as well as aggradation. Synchronous changes in depositional style, structural deformation, sandstone composition, and rates of tectonic subsidence of the Oregon Coast Range basin are interpreted to record the transition from collisional trench-fill deposition to a subsiding forearc basin. The Tyee Formation was deposited after collision was complete and yet is rotated as much as the seamounts on which it lies; therefore, rotation must have occurred subsequent to collision. Since these sediments were partially derived from the Idaho Batholith region, the Oregon Coast Range probably lay much farther east during deposition and subsequently rotated westward to its present position. Tectonic rotation of the Oregon Coast Range may have resulted from continental extension that began in the Pacific Northwest about 50 Ma. Paleogeographic reconstructions show that basin development was synchronous with regional extension, arc migration, and tectonic rotation throughout the Pacific Northwest.
Type:
text; Dissertation-Reproduction (electronic); maps
Keywords:
Geology -- Oregon.; Geology, Structural.; Plate tectonics.; Geology, Stratigraphic -- Eocene.; maps
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Geosciences; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Dickinson, Bill

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleSEDIMENTARY RESPONSE TO EOCENE TECTONIC ROTATION IN WESTERN OREGON (WASHINGTON, PACIFIC NORTHWEST, PETROLOGY).en_US
dc.creatorHELLER, PAUL LEWIS.en_US
dc.contributor.authorHELLER, PAUL LEWIS.en_US
dc.date.issued1983en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractPublished paleomagnetic studies have shown that the Oregon Coast Range has rotated 60° clockwise since middle Eocene time, probably by pivoting either during collision of a seamount terrane or during an episode of asymmetric extension within western North America. Eocene sedimentary deposits within the Oregon Coast Range basin, in particular the Tyee Formation, document changes in basin evolution that provide geologic constraints for proposed rotation models. The Tyee Formation comprises an arkosic petrofacies which is different from underlying lithic sandstones that were derived from the adjacent Klamath Mountains. Isotopic study of sandstones of the arkosic petrofacies, including Sm-Nd, Rb-Sr, K-Ar, and ¹⁸O analyses, indicate that much of the sandstone was not derived from the Klamath Mountains or nearby Sierra Nevada. The source area most likely included S-type granites of the Idaho Batholith. Lithofacies within the Tyee Formation include a sandy deltaic system to the south, a thin muddy shelf/slope sequence farther north, and a thick basinal sequence of sandy high-density turbidites that grade northward into low-density turbidites. Absence of facies segregation within the turbidite sequence precludes application of classical deep-sea fan depositional models and forms the basis for the delta-fed submarine ramp model introduced here. Delta-fed submarine ramps are short-lived sandy systems that result from rapid rates of progradation as well as aggradation. Synchronous changes in depositional style, structural deformation, sandstone composition, and rates of tectonic subsidence of the Oregon Coast Range basin are interpreted to record the transition from collisional trench-fill deposition to a subsiding forearc basin. The Tyee Formation was deposited after collision was complete and yet is rotated as much as the seamounts on which it lies; therefore, rotation must have occurred subsequent to collision. Since these sediments were partially derived from the Idaho Batholith region, the Oregon Coast Range probably lay much farther east during deposition and subsequently rotated westward to its present position. Tectonic rotation of the Oregon Coast Range may have resulted from continental extension that began in the Pacific Northwest about 50 Ma. Paleogeographic reconstructions show that basin development was synchronous with regional extension, arc migration, and tectonic rotation throughout the Pacific Northwest.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.typemaps-
dc.subjectGeology -- Oregon.en_US
dc.subjectGeology, Structural.en_US
dc.subjectPlate tectonics.en_US
dc.subjectGeology, Stratigraphic -- Eocene.en_US
dc.subjectmaps-
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGeosciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorDickinson, Billen_US
dc.contributor.committeememberConey, Peteren_US
dc.contributor.committeememberKidwell, Susanen_US
dc.contributor.committeememberBaker, Victoren_US
dc.contributor.committeememberSmiley, Terahen_US
dc.identifier.proquest8401264en_US
dc.identifier.oclc690197116en_US
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