HR: 0800h
AN: GP41A-0812    [Abstracts]
TI: Mesozoic oceanic terranes - key to our understanding of Meso-Pacific History
AU: * Krylov, K A
EM: kirillkrylov@earthlink.net
AB: Along the eastern Pacific margin of Asia Mesozoic oceanic complexes are widely distributed. The structure and geometry of these accreted oceanic complexes vary from: (1) dismembered ophiolite nappes; (2) blocks in serpentinite melange and olistostromes; (3) offscraped fragments of the oceanic crust in a sheared argillite matrix which is interpreted to represent an accretionary prism sequence. The sedimentary strata associated with the oceanic complexes are mostly various types of siliceous sediments: radiolaria chert and jasper, grey cherts and siliceouc argillite and in lesser quantities, limestones. In many ophiolitic sections, sediments form the cover sequences of the various MORB-type lavas. The following sedimentary sequences have been mapped and described in the Koryak Mountains: The Pekul'ney Ridge, Mainitz, Alkatvaam, Ekonay, Kuyul (Penzhina) Ukelayat and Olutor terranes. Similar sequences are known from Kamchatka, Sakhalin, Taigonos and Elistratov Peninsulas, in Udskaya Guba, Priamurie, and in Sikhote-Alin. The composition and character of microfauna in these mostly pelagic sequences indicate accumulation of siliceous strata at lower latitudes than their present localities (Bragin, 1991; Vishnevskaya, 1990). Paleomagnetic data available on the oceanic complexes tend to support their allochthoneity, and indicate significant northward motion. As such, these oceanic complexes are particularly important for paleotectonic reconstructions of the Paleo Pacific ocean floor. Analysis of all data and paleomagnetic results from Late Jurassic - to Cretaceous accreted oceanic units allow one to conclude that the kinematics of the Koryak and Kamchatka oceanic terranes and their accretion is defined by the presence and interactions of four oceanic plates, the Izanagi, Farallon, Kula and Pacific plates with the continental margins of North American and Siberian continents. The older, Triassic - to Middle Jurassic complexes are the main source of information on the composition and structure of the more ancient Meso-Pacific Ocean. Correlation and age of these oceanic fragments together with a study of their structure and their time of accretion, provides a unique data set that is much more complete than that possible with deep-ocean drilling of Pacific Ocean floor.
UR: http://pangea.stanford.edu/research/structure/
DE: 8105 Continental margins and sedimentary basins
DE: 8157 Plate motions--past (3040)
DE: 3655 Major element composition
DE: 1525 Paleomagnetism applied to tectonics (regional, global)
DE: 1635 Oceans (4203)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting