HR: 0800h
AN: GP41A-0826    [Abstracts]
TI: Phanerozoic Paleomagnetic Reconstruction of Selected Parts of the Kolyma-Omolon Superterrane (Northeast Russia)
AU: * Kolosev, E
EM: kolesov@neisri.magadan.ru
AF: North-East Interdisciplinary Scientific Research Institute, FEB RAS, NEISRI, 16 Portovaya Street,, Magadan, 685000 Russian Federation
AB: There are now sufficient paleomagnetic data for certain terranes of Northeast Russia (Omulevsky, Prykolymsky and Omolonsky terranes) to be able to determine temporal variations of paleolatitude and trace the dynamics of the displacement of these terranes over the whole Phanerozoic. The following paleotectonic development of the terranes studied is suggested: In Early Paleozoic (Cambrian - Early Ordovician Period) Prykolymski was located between 10ø and 20ø S. near the present day Northeast margin of the North Asian craton. In Early Silurian the Omulevsky terrane was located between the equator and 10ø N, but by the end of Silurian it approached the craton and was located between 10ø and 20ø N near the current east margin of the latter. The Prykolymsky terrane has the same paleolatitude and location as was determined for the Omulevsky terrane for Late Silurian time. In the Middle Devonian their locations remained almost identical (between 30ø and 40ø N.). For Late Devonian time there are also data for Omolonsky. This terrane together with the Omulevsky and Prykolymsky terranes was located (at least from the Late Devonian) near the northern or northeast margin of North Asian craton in the west hemisphere between 30ø and 40ø N. and all three were rifting in a northerly direction. The data indicate the Prykolymsky terrane to be close to the craton in the Cambrian, maybe even in Riphean. For the Omulevsky terrane close correspondence with the craton is seen Ordovician time, data for earlier times being unavailable. Prykolymsky in the Middle-Late Devonian was rotated counterclockwise relative to the craton by 132ñ17.7ø, for the Omulevsky terrane, from the Silurian to the Permian a counterclockwise rotation of 85-100ø is observed. The Omolonsky terrane in Permo-Triassic turned 150ø counterclockwise relative to the craton. During the Late Carboniferous and Permian times the scenario of the relative locations of the craton and blocks under study did not undergo significant changes. The Prykolymsky and Omulevsky terranes were located near the craton between 40ø - 50ø N. The Prykolymsky terrane in the Late Paleozoic was turned counterclockwise by 67,7ñ28.5ø relative to the craton. There are conflicting data for Triassic time for the Omolonsky terrane. During the Jurassic period Omolonsky terrane was located at 60o N paleolatitude and by the Late Cretaceous it moved to 75ø N. Omulevsky and Prykolymsky terranes were located tentatively on the same latitudes and this time. Paleotectonic evolution of the terranes described above is proposed based on the analysis of only paleomagnetic data. For complete justification (or refutation) of these locations it is necessary to involve additional geological information. The studies were supported by the Russian Foundation for Basic Research (project 03-05-96012 Arctica) and Far East Branch Russian Academy of Science (grant 04-3A-08-014).
DE: 9315 Arctic region
DE: 9320 Asia
DE: 8155 Plate motions--general
DE: 1525 Paleomagnetism applied to tectonics (regional, global)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting