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GEOREF RECORD

Internal deformation of the southern Gorda Plate; fragmentation of a weak plate near the Mendocino triple junction

Sean P. S. Gulick, Anne S. Meltzer, Timothy J. Henstock and Alan Levander
Internal deformation of the southern Gorda Plate; fragmentation of a weak plate near the Mendocino triple junction
Geology (Boulder) (August 2001) 29 (8): 691-694

Abstract

North-south compression across the Gorda-Pacific plate boundary caused by the northward-migrating Mendocino triple junction appears to reactivate Gorda plate normal faults, originally formed at the spreading ridge, as left-lateral strike-slip faults. Both seismically imaged faults and magnetic anomalies fan eastward from approximately N20 degrees E near the Gorda ridge to approximately N75 degrees E near the triple junction. Near the triple junction, the Gorda plate is faulted pervasively and appears to be extending east-southeast as it subducts beneath North America. Continuation of northeast-southwest-oriented deformation in the southern Gorda plate beneath the continental margin contrasts with the northwest-southeast-trending structures in the overlying accretionary prism, suggesting partial Gorda-North American plate decoupling. Southeast of the triple junction, a slabless window is generated by removal of the subducting Gorda plate. Southwest of the triple junction, the Pacific plate acts as a rigid barrier forcing southern Gorda crust to rotate clockwise, fragment, and flow into the slabless window. Net clockwise rotation of the southern Gorda crust forms a boundary with the nonrotating northern Gorda plate, which is observed as a bend in the magnetic anomalies. This boundary, which is compressional on the western end and extensional to the east, may separate the stress regime of the southern Gorda plate from the remainder of the Cascadia subduction zone.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 29
Serial Issue: 8
Title: Internal deformation of the southern Gorda Plate; fragmentation of a weak plate near the Mendocino triple junction
Affiliation: Lehigh University, Department of Earth and Environmental Sciences, Bethlehem, PA, United States
Pages: 691-694
Published: 200108
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 21
Accession Number: 2001-076331
Categories: Solid-earth geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch maps
N40°30'00" - N41°30'00", W126°00'00" - W125°00'00"
Secondary Affiliation: Rice University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200124
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