Volume 26, 6, 2007 |
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V.M. Nikiforov, I.V. Dmitriev. Geoelectrical section of tectonosphere in the junction zone of the Sea of Japan depression and continental framing 3 T.V. Volodkova. The features of magmatism of Kunashir Island (Kuril Island arc) from aerogeophysical evidence 15 Ye.A. Bessonova. Application of micromagnetic mapping for identification of heterogeneities of geologic and anthropogenic genesis in contemporary sediments of the coastal zone of Expedition Bay (Pyotr Velikiy Strait, Sea of Japan) 38 A.V. Lozhkin, P.M. Anderson, T.V. Matrosova, P.S. Minyuk, J. Brigham-Grette, M. Melles. A continuous record of environmental change in Chukotka during the last 350 thousand years 53 V.I. Anoikin, G.L. Kirillova, L.P. Eichwald. New conceptions of the composition, structure and age of the Lower Amur fragment of the Late Jurassic-Early Cretaceous accretionary prism (Far East) 60 B.I. Pavlyutkin. The Ust’-Davydovskaja suite as the crucial Paleogene straton of Primorye, the Russian Far East 78 M.V. Goroshko, V.A. Guryanov. Ore mineralization in the zone of pre-Riphean structural stratigraphic unconformity and the Lower Riphean platform cover of the Uchur-Maya depression (south-eastern part of the Siberian platform) 93 Chronicles V.E. Kirillov, G.L. Kirillova, V.G. Bykov, V.A. Bormotov, L.I. Popeko, L.F. Mishin, Yu.F. Malyshev. Tectonics and Metallogeny of the Circum-North Pacific and Eastern Asia 111 Index of papers published in the journal in 2007 115 V.M. Nikiforov, I.V. Dmitriev Geoelectrical section of tectonosphere in the junction zone of the Sea of Japan depression and continental framing New data on the deep geoelectrical structure of tectonosphere in the junction zone of the Sea of Japan and continental structures are demonstrated. Digital modeling of the geoelectrical section was performed on the basis of the unique data set which was obtained via monitoring of electrical field variations in the JASC underwater telecommunication cable and in land cables in the Primorye region. The data were collected simultaneously with the registration of geomagnetic variations at VLA, KHB and MMB observatories and at a PPI stationary site. Additionally, data from 80 field MTS sites at the Khanka massif and Sikhote-Alin fold area were used. T.V. Volodkova The features of magmatism of Kunashir Island (Kuril Island arc) from aerogeophysical evidence The use of the maps of natural radioactive elements (RAE) content at a scale of 1:500000 confirmed the existence of transverse volcanic zoning of the Kuril island arc (KIA). Trends of RAE relations of the KIA magmatic complexes were calculated, and their conditionality by fluidization processes was proved. According to aerogeophysical evidence (RAE relations maps, manetic field), the principal cyclic sequence of active volcanoes and magmatism was established on Kunashir Island. Multicyclic volcanoes related to mantle sources are characterized by typical predominance of volcanic assemblages of calc-alkaline composition, the development of processes of “deposition of magnetite”, and weak distribution of metasomatites. The other volcanoes that are related to crust sources are characterized by development of assemblages of a high calcareous character and thick hydrothermal metasomatic systems. Ye.A. Bessonova Application of micromagnetic mapping for identification of heterogeneities of geologic and anthropogenic genesis in contemporary sediments of the coastal zone of Expedition Bay (Pyotr Velikiy Strait, Sea of Japan The comprehensive analysis of multi-parameter and diverse information involving the results of large-scale magnetic survey allowed restoration of the features of sedimentation in the coastal zone of Expedition Bay at the final stage of development of the geological environment. Geological and anthropogenic sources of an abnormal magnetic field are distinguished on the basis of the analysis of results of measurements of the module of a complete vector of the geomagnetic field. A conclusion is drawn on the polygenetic character of accumulation of sedimentary material in the cultural layer of the Kraskinskiy site of an ancient settlement - the largest archaeological monument of the Bohai state in Primorye. For the first time in the south of the Russian Far East the internal topography of the cultural layer of the medieval flat site of the ancient settlement is reconstructed by micromagnetic survey, and the location of the most informative objects necessary for understanding cultural-historical development of the archaeological monument is defined. A.V. Lozhkin, P.M. Anderson, T.V. Matrosova, P.S. Minyuk, J. Brigham-Grette, M. Melles A continuous record of environmental change in Chukotka during the last 350 thousand years The comprehensive study of the upper 1283 cm of sediment from Lake El’gygytgyn, which formed nearly 4 million years ago following a meteorite impact in northern Chukotka, yielded the first continuous record of extreme changes in Beringian climate and vegetation from the middle Middle Pleistocene to Recent time (marine isotope stage equivalent of 1-7 and the upper part of isotope stage 8). During this period, the climate was warmer than at present between 8600 and 10700 14C years BP and during the Late Pleistocene interglaciation (isotope substage 5e, 116-128 thousand years ago). In 2003, the German-Russian-USA international expedition continued studying sediments of Lake El’gygytgyn to obtain new evidence of the change in the vegetation cover in the Middle Pleistocene and the first information on the Middle Pleistocene interglaciation (isotope stage 9, 297-347 thousand years ago). Pollen spectra characterizing the Middle Pleistocene interglaciation are similar to spectra of the early stage of the Middle Pleistocene interglaciation and the climatic optimum in the Pleistocene to Holocene transitional period. The climatic history of Lake El’gygytgyn is the basis for stratigraphic reconstructions and correlations in the eastern sector of the Arctic. These data also expand understanding of climatic changes within the international projects “Pole-Equator-Pole Paleoclimate Project,” “Past Global Changes Project,” and others. V.I. Anoikin, G.L. Kirillova, L.P. Eichwald New conceptions of the composition, structure and age of the Lower Amur fragment of the Late Jurassic-Early Cretaceous accretionary prism (Far East) Based on field observations and the study of conodont and radiolarians microfauna, a new stratigraphic scheme for the Mesozoic of the Komsomolsk region (Priamurye, Far East) is proposed. The lower Khorpinskaya series (T2–J3) consists of two rock units: Boktorskaya (T2–J2) and Kholvasiyskaya ((J2-3 hl). The former is represented by pelagic chert with subordinate cherty-clay shale and volcanics about 400 m thick. The latter is made up of mainly siltstone and clay shale with rare intercalations and lenses of clay chert and cherty-clay shale. Its thickness is 500 m. The upper, Komsomolskaya series of terrigenous composition (Ê1) unites several suites (Gorinskaya, Pionerskaya, and Pivanskaya) with a total thickness of about 5 km. It is made up of intercalated sandstone, siltstone, and mudstone; turbidite (proximal to distal) may be common. The rocks contain abundant buchia fauna of Volgian-Valanginian age, and also carbonized vegetation detritus and flora of the Early Cretaceous habit. The described complex is characterized by the nappe-fold structure specific for the zones of interaction of oceanic and continental lithosphere plates. The coherent type of accretionary prisms prevails which mirrors the simple morphology of the oceanic plate. B.I. Pavlyutkin The Ust’-Davydovskaja suite as the crucial Paleogene straton of Primorye, the Russian Far East The issue of introduction and subsequent abolishment of the nomenclature combination known as the Ust’-Davydovskaya suite is examined. Geological data on the stratotype of the suite on Rechnoi Peninsula, Vladivostok area, are offered. The age of the Ust’-Davydovskaya suite is dated as Late Eocene based on micro- and macrofloral analysis. A new variant is suggested for correlation of sections of Tertiary deposits in different sectors of the Artem-Tavrichanka depression (typical locality of the Ust’-Davydovskaya suite) allowing elimination of contradictions between floral and faunal evidence. M.V. Goroshko, V.A. Guryanov Ore mineralization in the zone of pre-Riphean structural stratigraphic unconformity and the Lower Riphean platform cover of the Uchur-Maya depression (south-eastern part of the Siberian platform Metallogeny of the zone of pre-Riphean structural stratigraphic unconformity and the Lower Riphean platform cover of the Uchur-Maya depression in the south-eastern part of the Siberian platform is considered. Information is offered on the features of the geologic structure of the region, ore localizing structures and wallrock alterations, ore composition and isotope age of mineralization. Extensive development of K-feldspar metasomatites has been recognized in the zone of structural stratigraphic unconformity, and their role as a source of ore elements during ore deposition has been identified. The staging of development of wallrock alterations and ore processes is examined. Typal occurrences of gold, uranium, copper and barium are characterized. The polyelemental composition of ore zones and element scattering aureoles at some ore occurrences is demonstrated. The main features of metallogeny of the zone of pre-Riphean structural stratigraphic unconformity and the Lower Riphean platform cover are intensity and a multistage character of processes of pre-ore preparation, polyelemental character of the ores, and favorable lithologo-structural conditions of ore deposition. |