HR: 0800h
AN: GP41A-0816    [Abstracts]
TI: Triassic terrigeneous deposits of Western Chukotka: sedimentation, mineral composition, deformations (NE Russia)
AU: * Tuchkova, M I
EM: tuchkova@ginras.ru
AF: Geological Intitute, Pyzhevsky pereulok 7, Moscow, 119017 Russian Federation
AU: Bondarenko, G Y
EM: : g.bondarenko@promgaz.gazprom.ru
AF: Intitute "PROMGAZ", Nametkina ulitsa 6, Moscow, 117420 Russian Federation
AU: Miller, E L
EM: miller@pangea.stanford.edu
AF: Dept. Geological and Environmental Sciences, Stanford University, Stanford, CA 94305 United States
AU: Katkov, S M
EM: sergkat@yandex.ru
AF: Geological Intitute, Pyzhevsky pereulok 7, Moscow, 119017 Russian Federation
AB: Chukotka's Triassic terrigeneous deposits form three different complexes: Lower-Middle Triassic complex, Upper Triassic Karnian complex and Upper Triassic Norian complex. The studied part of western Chukotka is composed of variably deformed, folded and cleaved rhythmic deposits. All the complexes are represented by rhythmic intercalation of sandstones, siltstones and mudstones. Unfortunately, macrofaunas are not numerous in the Triassic deposits, and in some cases deposits are dated by analogy or comparison to the units dated with macrofaunas. Triassic deposits are composed of hemipelagic sediments, low-density flows, high-density flows, and shelf facies associations. Relationships between the facies were reconstructed with structural researches and data. During the Triassic, sedimentation was represented by continental slope progradation. Petrographic study of mineral composition has established the sandstones as graywackes (classification diagram by Shutov, 1972). Although Triassic sandstones are similar in outcrops and classification, the enclosed rocks fragment grains are different. Rock fragment grains in sandstones are composed of diverse lithologies, and we chart the evolution of their composition from the Lower to the Upper Triassic. Sandstones with (clasts) rock fragments of lower metamorphic grade rocks dominate at the base of Triassic deposits, sandstones with fragments of higher grade metamorphic rocks dominate in the Later Triassic deposits. This different show us that the Triassic represents an unroofing sequence where(sours of) erosional processes that produced the clastic material eroded more deeply buried rocks through time. Supported by RFFI (grants 02-05-64217, 03-05-64915).
DE: 9315 Arctic region
DE: 9609 Mesozoic
DE: 3675 Sedimentary petrology
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting