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Dextral shear and north-directed crustal shortening defines the transition between extensional and contractional provinces in north-central Oregon

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dc.contributor.advisor Meigs, Andrew J.
dc.creator Johnson, Ajeet K.
dc.date.accessioned 2011-04-25T17:11:45Z
dc.date.available 2011-04-25T17:11:45Z
dc.date.copyright 2011-01-18
dc.date.issued 2011-04-25
dc.identifier.uri http://hdl.handle.net/1957/20928
dc.description Graduation date: 2011 en_US
dc.description.abstract Distributed deformation in the backarc of Cascadia is complex. Off the west coast lies the Cascadia convergent margin. East of the plate boundary, clockwise rotation of the Oregon Coast Range block with respect to stable North America influences backarc deformation, causing extensional faults in southeast Oregon, contraction folding in southeast Washington and a transition between the two opposing styles in north-central Oregon. Folding of the Mutton Mountain and Tygh Ridge anticlines commenced post 15.5 Ma and was most active between ~8.4 and 2.6 Ma. From Mutton Mountain to Tygh Ridge anticlines, minimum estimates of north-south shortening give an average shortening rate of 0.14 mm/yr from 8.4 to 2.6 Ma. Change in strike and dextral offsets of axial traces reflects a broad shear zone transferring motion between two relatively stable blocks; the Ochoco Mountain block and the Cascade arc. The transition region is characterized where dextral shear accommodates for an west-east velocity gradient. GPS velocity vectors indicate a difference of 1.0 mm/yr from the northern Basin and Range to the north and ~0.8 mm/yr from west to east. en_US
dc.language.iso en_US en_US
dc.subject Structure en_US
dc.subject Tectonics en_US
dc.subject Oregon en_US
dc.subject Tygh Ridge en_US
dc.subject Rotation en_US
dc.subject geology en_US
dc.subject Folding en_US
dc.subject Mutton Mountain en_US
dc.title Dextral shear and north-directed crustal shortening defines the transition between extensional and contractional provinces in north-central Oregon en_US
dc.type Thesis/Dissertation en_US
dc.degree.name Master of Science (M.S.) in Geology en_US
dc.degree.level Master's en_US
dc.degree.discipline Science en_US
dc.degree.grantor Oregon State University en_US
dc.contributor.committeemember Grunder, Anita
dc.contributor.committeemember Trehu, Anne


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