HR: 16:30h
AN: GP44A-03    [Abstracts]
TI: Timing and Kinematics of Eocene Olyutorsky Arc-Continent Collision
AU: * Soloviev, A V
EM: solov@ilran.ru
AF: Geological Institute, Pyzhevsky, 7, Russia, 119017 Russian Federation
AU: Hourigan, J K
EM: jeremy.hourigan@yale.edu
AF: Dept. of Geology and Geophysics, P.O. Box 208109 Yale University, New Haven, CT 06511 United States
AU: Garver, J I
EM: garverj@union.edu
AF: Department of Geology, Olin Building Union College 807 Union Ave , Schenectady, NY 12308 United States
AU: Brandon, M T
EM: mark.brandon@yale.edu
AF: Dept. of Geology and Geophysics, P.O. Box 208109 Yale University, New Haven, CT 06511 United States
AB: The collision of the Cretaceous Olyutorsky terrane with the northeast Asian margin was critical event in Cenozoic evolution of the northern Pacific. Remnants of the far-traveled Olyutorsky terrane can be traced for almost the entire length of the Kamchatka Peninsula, and likely extend eastward into the Bering Sea as the Shirshov and Bowers Ridge for an aggregate length of ~ 3000 km. The Vatyna Thrust representing the collisional suture between Ukelayat Flysch in the lower plate and Olyutorsky arc can be traced for 2000 km from southern Koryakia to Kamchatka. The Olyutorsky terrane comprises Late Cretaceous MORB-type basalt, chert, island-arc volcanic rocks, and associated zoned Alaskan-type intrusions. The Ukelayat flysch consists of a 10-to-15 km-thick zone of deformed Late Cretaceous to Eocene turbidites. In southern Koryakia and the Lesnovsk highlands brittle fault zone kinematic indicators suggest that the initial phase of collision was controlled by oblique arrival of the Olyutorsky terrane to southeast-facing NE Asian margin. Subsequently, orthogonal convergence prevailed as indicated by later NW-SE directed imbricate thrusting and NE-SW trending tight to isoclinal folds developed in the Ukelayat flysch. Stratigraphic and cross-cutting relationships in the Lesnovsk highlands provide tight control on the timing of thrusting. Here, detrital fission-track grain-ages and biostratigraphic data suggest that the deformed Lesnaya group rocks span the Upper Cretaceous to Middle Eocene. Further, the Vatyna Thrust is cross-cut by the Shamanka granitic massif and unconformably overlain by Kinkil Formation felsic volcanic rocks both of which yield 45 Ma U/Pb zircon ages, placing a Middle Eocene lower age limit on the timing of arc obduction. Low temperature thermochronologic data indicate that post-orogenic exhumation in this region proceeded slowly (~ 50 m/myr). Geochronologic data and regional structural observations from Sredinny Range (southern Kamchatka) indicate that collision began in the Late Paleocene. Syn-to-post collisional exhumation was initially rapid (~3 km/myr) in the Middle Eocene. In total, the high-grade core of the Sredinniy Range has been exhumed to depths of ~30 km. These new timing constraints indicate that arc obduction proceed diachronously. To explain this difference in the collisional and post-collisional tectonic histories, we argue that a transform fault likely separated the southern and northern portions of Olyutorsky terrane.
DE: 8005 Folds and folding
DE: 8025 Mesoscopic fabrics
DE: 8105 Continental margins and sedimentary basins
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting