Collaborative Research: Cenozoic Evolution of the Aleutian-Kamchatka Junction

Yale University, New Haven CT

Investigators

Abstract

Abstract OPP-9911925 Brandon OPP-9911910 Garver This is a collaborative proposal with Principal Investigators from Yale University and Union College. This proposal is receiving joint funding from the Baltic States, Bulgaria, Poland, Independent States of the Former Soviet Union, International Programs. The Kamchatka region contains a detailed, well-exposed record of the plate tectonic evolution of the north Pacific basin, essential for resolving the origin of the Aleutian volcanic arc and major geologic features beneath the Bering Sea. The Kamchatka is underlain by at least two exotic island arcs, which formed at low latitudes during the late Cretaceous and early Tertiary, 90-60 million years ago (Ma), and then moved north, colliding with the northeast Russian continental margin. The first to collide was the Olyutorsky island arc which overrode the Russian margin along the Vatyna thrust about 45 Ma. The Cape Kamchatka arc collided next. The collision is poorly resolved, but may have started in late Miocene (1 5 Ma) and appears to be presently active at the Aleutian-Kamchatka junction. This collision event is complicated because the pieces of the collided arc are isolated along the prominent capes on the east side of the Kamchatka Peninsula and may also include the Komandorsky Islands and western Aleutian Islands. The tectonic zones that presently border these exotic arcs contain a valuable record of the timing and kinematics of the collisions. The Principal Investigators have studied the age and kinematics of part of the Vatyna thrust and will continue to study both collision zones in the southern transect across the Kamchatka Isthmus to Cape Kamchatka to establish the ages for the collisional history of the Olyutorsky and Cape Kamchatka arcs. They have selected three target areas: 1) southern continuation of the Vatyna thrust in the Lesnovsk Highland of the Kamchatka Isthmus; 2) the east side of Karaginsky Island which exposes the Vetiovsky complex, a poorly dated subduction complex that formed outboard of the Olyutorsky arc; and 3) west of Cape Kamchatka where the Vetiovsky subduction complex has been pinched between the Olyutorsky arc and the more outboard Cape Kamchatka arc. They will date the continuation of the Vetlovsky complex from Karaginsky Island to determine how and when the Eocene to Miocene Tyushev basin began to overlap the older tectonic units in this area. This information should provide a record of the first arrival of the Cape Kamchatka arc at the Kamchatka margin. They will use fission-track dating of detrital zircons from continental-derived sandstones. Dating of individual zircons will allow them to statistically isolate the youngest fraction of grain ages. The dating method is precise (relative standard error - 3.5%) and will provide age information about a tectonically important group of rocks. The method will also be used to date volcanic rocks and plutons that crosscut and seal the Vatyna thrust in the Lesnovsk highlands. Some ages will be supplemented by more expensive high precision uranium/lead zircon ages.