TY - JOUR
T1 - A rift-edge facies of the late jurassic rogue-chetco arc and josephine ophiolite, Klamath Mountains, oregon
AU - Yule, J. Douglas
AU - Saleeby, Jason B.
AU - Barnes, Calvin G.
PY - 2006
Y1 - 2006
N2 - The western Jurassic belt of the Klamath Mountains represents one of the Earth's best-preserved exposures of ancient marginal ocean basin lithosphere and chiefly consists of the coeval Rogue-Chetco volcanic-plutonic oceanic arc and Josephine ophiolite. This Late Jurassic ocean basin is hypothesized to have formed in response to rifting that initiated at ca. 165 Ma along the western margin of North America, disrupting a Middle Jurassic arc that had been constructed on older Klamath terranes and forming a marginal ocean basin with an active arc, inter-arc basin, and remnant arc. Previous workers characterized a "rift-edge" facies in the remnant-arc region. This chapter describes field, age, and geochemical data that suggest that a similar rift-edge facies exists in the vicinity of the active arc, on the opposite side of the marginal basin. The rift-edge facies in the active arc setting consists of two main lithotectonic units, herein named informally as the Onion Camp complex and Fiddler Mountain olistostrome. The Onion Camp complex is partly composed of a characteristic metabasalt and red chert association. Red chert yielded scarce radiolarians of Triassic(?) and Early Jurassic age. A distinct chert-pebble conglomerate occurs at scarce localities within metasedimentary rocks. Concordant, composite bodies of amphibolite and serpentinized peridotite represent another distinctive feature of the Onion Camp complex. The metamorphic and lithologic features of the Onion Camp complex are similar to the lower mélange unit of the Rattlesnake Creek terrane, and the units are interpreted to be correlative. The Fiddler Mountain olistostrome is composed of Late Jurassic (Kimmeridgian?) pelagic and hemipelagic rocks interlayered with ophioliteclast breccia and megabreccia, similar in character to olistostromal deposits associated with the rift-edge facies of the remnant arc. The occurrence of the Rattlesnake Creek terrane and an associated olistostromal deposit within the western Jurassic belt of southwestern Oregon may therefore represent the rift-edge facies in the active arc setting, at the transition between the Rogue-Chetco arc and Josephine ophiolite, further corroborating previous models for the Late Jurassic tectonic evolution of the Klamath Mountains.
AB - The western Jurassic belt of the Klamath Mountains represents one of the Earth's best-preserved exposures of ancient marginal ocean basin lithosphere and chiefly consists of the coeval Rogue-Chetco volcanic-plutonic oceanic arc and Josephine ophiolite. This Late Jurassic ocean basin is hypothesized to have formed in response to rifting that initiated at ca. 165 Ma along the western margin of North America, disrupting a Middle Jurassic arc that had been constructed on older Klamath terranes and forming a marginal ocean basin with an active arc, inter-arc basin, and remnant arc. Previous workers characterized a "rift-edge" facies in the remnant-arc region. This chapter describes field, age, and geochemical data that suggest that a similar rift-edge facies exists in the vicinity of the active arc, on the opposite side of the marginal basin. The rift-edge facies in the active arc setting consists of two main lithotectonic units, herein named informally as the Onion Camp complex and Fiddler Mountain olistostrome. The Onion Camp complex is partly composed of a characteristic metabasalt and red chert association. Red chert yielded scarce radiolarians of Triassic(?) and Early Jurassic age. A distinct chert-pebble conglomerate occurs at scarce localities within metasedimentary rocks. Concordant, composite bodies of amphibolite and serpentinized peridotite represent another distinctive feature of the Onion Camp complex. The metamorphic and lithologic features of the Onion Camp complex are similar to the lower mélange unit of the Rattlesnake Creek terrane, and the units are interpreted to be correlative. The Fiddler Mountain olistostrome is composed of Late Jurassic (Kimmeridgian?) pelagic and hemipelagic rocks interlayered with ophioliteclast breccia and megabreccia, similar in character to olistostromal deposits associated with the rift-edge facies of the remnant arc. The occurrence of the Rattlesnake Creek terrane and an associated olistostromal deposit within the western Jurassic belt of southwestern Oregon may therefore represent the rift-edge facies in the active arc setting, at the transition between the Rogue-Chetco arc and Josephine ophiolite, further corroborating previous models for the Late Jurassic tectonic evolution of the Klamath Mountains.
KW - Josephine ophiolite
KW - Klamath mountains
KW - Late jurassic
KW - Olistostromal deposits
KW - Oregon
KW - Radiolarians
KW - Rattlesnake creek terrane
KW - Rifting
KW - Rogue-chetco volcanic-plutonic arc
KW - Sncient marginal ocean basin
UR - http://www.scopus.com/inward/record.url?scp=73949092411&partnerID=8YFLogxK
U2 - 10.1130/2006.2410(03)
DO - 10.1130/2006.2410(03)
M3 - Article
AN - SCOPUS:73949092411
SN - 0072-1077
VL - 410
SP - 53
EP - 76
JO - Special Paper of the Geological Society of America
JF - Special Paper of the Geological Society of America
ER -