Volume 19, 2, 2000
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Volume 19, 2, 2000 |
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Geophysics
G.I. Anosov, B.Ch. Suk ,V.V. Argentov, S.K. Bikkenina , V.V. Zhigulev , K.F. Sergeev . Structure of eastern shelf of the Korean Peninsula by seismic data 3
V.L. Lomtev, V.E. Kononov, V.N. Ageev.New data on the structure of the southern Lord Howe Ridge (the Tasman Sea) 17
GeomorphologyV.B. Spektor, N.T. Bakulina, L.P. Anosova. Pliocene ?rogenesis ?ycle in the Cherski Mountain System (North?ast of Russia) 32
Sedimentology and GeochemistryY.D. Zakharov, N.G. Boriskina, A.V.Ignatyev, T.B. Afanasyeva, G.I. Buryi, V.Y. Vuks, G.V. Kotlyar, E.S. Panasenko, A.M. Popov, T.A. Punina, A.K. Cherbadzhy. Triassic carbonates in North Caucasus and Primorye: stable oxygen and carbon isotopes, Ca/Mg ratio and correlation 47
S.A.Gorbarenko, A.N.Derkachev, A.S.Astakhov, J.R. Sauton, D.Nurnberg, V.V. Shapovalov-Chuprynin. Lithostratigraphy and tephrochronology of the Upper Quaternary deposits in the Sea of Okhotsk 58
N.G. Razjigaeva, T.A. Grebennikova, V.D. Bazarova, L.D. Sulerzhitskiy, L.M.Mokhova, L.A. Ganzeiy, V.S.Pushkar, A.V. Chernov. Terrestrial Late Pleistocene deposits of the Kunashiri Islands, Kurile Islands 73
N.V. Astakhova. Geochemical peculiarities of the sediments in the Deryugin trough, the Sea of Okhotsk 87
Petrology and MineragenyI.V.Buchko. PGE distribution types in stratified ultrabasite-basite intrusions within the Stanovoy fold block system, an example from the Vesselkinsky massif 94
E.L.Schkolnik, L.B.Kherschberg, M.M.Zadornov, O.V.Chudaev.The phosphorites of Dalmorgeo guoyt in the Magellan seamounts of the Pacific ocean 101
ReviewsV.S.Vishnevskaya. Problems of Nassellaria classification: biochemical peculiarities of the evolution 109
G. I. Anosov, B. Ch. Suk, V. V. Argentov, S.K. Bikkenina, V. V. Zhigulev, K. F. Sergeyev
Structure of eastern shelf of the Korean Peninsula by seismic data
The paper presents results of seismic refraction survey carried out on the eastern shelf of the Korean Peninsula in spring, 1993, within the frames of the joint Russian-South Korean projects on study of deep structure of the Tsushima depression in the Japan Sea. Observations have been carried out by research vessel "Morskoi Geofizik" using self-contained bottom seismometers and pneumatic radiator (the working camera capacity of 30 dm3).
The data obtained and the available seismic reflection data allow to determine the upper crust structure and to study interrelation between the shelf structures and the Tsushima depression.
On the basis of a set of available seismic and geological data the question is stated on reestimation of possible oil-and-gas perspectives in the eastern shelf of the Korean Peninsula and the additional geophysical investigations are recommended aimed at verifying such perspectives.
V.L. Lomtev, V.E. Kononov, V.N. Ageev
New data on the structure of the southern Lord Howe Ridge (the Tasman Sea)
The structure of the Bellona trough area is analysed from continuous seismic and drilling data. Seismostratigraphy, seismofacies, and depositional environments are investigated. Oil and gas fields are supposed in coastal Late Eocene-Early Oligocene sediments and eluvial horizons of the paleoland buttes. Manifestations of a giant gas field have been recorded near the southern Shatsky Rise and Darwin paleoland in northeastern East Marianna basin by continuous seismic data.
V.B. Spektor, N.T. Bakulina, L.P. Anosova
Pliocene orogenic cycle in the Cherskiy Mountain System (Northeast of Russia)
During the Pliocene, the Cherskiy Range survived orogenic cycle which began with intensive upward movements accompanied by gravitational nappes and overthrusts as well as folded deformations of the Miocene and more ancient deposits, and terminated with relief lowering and formation of a regional planation surface. This conclusion is based on the analysis of facies and thicknesses of the Neogene deposits in central Cherskiy Range and the adjacent Momsky and Upper-Nersky depressions. Available geological and geomorphologic data allow to draw a conclusion that the range surface lowering and planation in the second half of the Pliocene was mainly accounted for by isostatic subsidence and in a lesser extent by erosional and glacial cut and sediment accumulation.
Yu.D. Zakharov, N.G. Boriskina, A.V.Ignatyev, T.B. Afanasyeva, G.I. Buryi, V.Y. Vuks, G.V. Kotlyar, E.S. Panasenko, A.M. Popov, T.A. Punina, A.K. Cherbadzhy
Triassic carbonates in North Caucasus and Primorye: stable oxygen and carbon isotopes, Ca/Mg ratio, and correlation
Some Early Dorashamian, Middle Olenekian, Early Anisian, Late Ladinian-?Early Carnian, Late Carnian, Early Norian, and Early Rhaetian events marked by an anomalously high value of d13? (2.5-6.9‰) and more or less expressed decline in Ca/Mg ratio in organogenic carbonates of the Tethyan Realm might be explained by high bioproductivity of the marine basins in the conditions of transgressions and warm climate. The highest d13? values identified in the Triassic limestones of Malaya Laba (6.9‰) and Sakhrai (4.2‰) River basins in North Caucasus and Russian Island (4.9‰) in Primorye region fall on the Middle Olenekian Tirolites-Amphistephanites Zone and its equivalents. Oxygen isotope analyses of brachiopod shells (with good preserved microstructure) from Nikitin and Urushten Formations show that the temperatures of the shallow water in marine basins in North Caucasus fluctuated during the Early Dorashamian from 23.8° to 24.2°C which is in accoedance with our previous paleotemperature data for the Paratirolites kittli Zone of Transcaucasia (22.0-24.2°C). Similar conditions appear to have occured in North Caucasus and South Primorye at least during the Middle Olenekian.
S.A.Gorbarenko, A.N.Derkachev, A.S.Astakhov, J.R. Sauton, D.Nurnberg,
V.V. Shapovalov-Chuprynin
Lithostratigraphy and tephrochronology of the Upper Quaternary deposits in the Sea of Okhotsk
Lithological horizons have been distinguished in sediments cores from different parts of the Sea of Okhotsk based on the primary description of sediments and smear slides, and analysis of the content of both calcium carbonate and organic carbon, and opal . Established sediment lithology has been correlated with oxygen isotope records and standard isotope scale and radiocarbon data by AMS method for three detailed studied cores. That allowed us to determine in detail the periods of carbonaceous and diatomaceous ooze in the Sea of Okhotsk.
Changes in magnetic susceptibility and sediment granulometric composition have been also compared with oxygen-isotope curves and radiocarbon dates. The results obtained confirm that variations of the magnetic susceptibility are related to oxygen-isotope stages thus being influenced by the climatic changes.
Tephra interlayers ?0, TR, K2, K3 have been singled out and identified by mineralogical analysis in all studied cores. Stratigraphic location of these tephra in detailed studied cores and their radiocarbon ages (8.1, 8.05, 26.8 and about 60 ka, respectively) provided base correlation between the interlayers and eruptions of the Kamchatka's and the Kurils' volcanoes. That allows us to use the former ones as time markers of the Sea of Okhotsk deep-sea sediments.
New lithostratigraphic and tephrochronologic data obtained, permitted correlation of the Upper Quaternary sediments from the Sea of Okhotsk.
N.G. Razjigaeva, T.A. Grebennikova, V.D. Bazarova, L.D. Sulerzhitskiy, L.M.Mokhova, L.A. Ganzeiy, V.S.Pushkar, and A.V. Chernov
Terrestrial Late Pleistocene deposits of the Kunashiri Islands, Kurile Islands
Terrestrial cover deposits of southern Kunashiri Island (Belozerskiy layers) include pyroclastic, alluvial, proluvial, lacustrine, and swamp facies. The deposits were accumulated during Late Plaistocecne active explosive volcanizm (48-30 ka. B.P.). Biostratigraphy (diatoms, spore and pollen), tephrostratigraphy and radiocarbon dating results are discussed. Some phases of vegetation development were distinguished. Dark-coniferous, small-leaved, spruce and broad-leaved forests reflect climatic conditions similar to or cooler than the present. Spore and pollen assemblages with abundant Betula sect. Nanae obtained from the buried soil from an eolian sandy loam indicate rigorous climatic conditions and development of mosaic landscapes (birch forests and shrub associations) at the end of the last Glacial Maximum. Paleoclimatic events on Kunashiri Island are correlated with Hokkaido, Sakhalin and Primorye.
N.V. Astakhova
Geochemical peculiarities of the sediments in the Deryugin trough, the Sea of Okhotsk
Microelement distribution in the upper (up to 5 m) Holocene-Upper Pleistocene sediments along the northern and southern sublatitudinal profiles located in the northern part of the Deryugin trough is discussed. The mathematical data processing of the chemical analysis has been made. On the basis of the cluster analysis, 16 elements have been combined into 5 geochemical groups. One of them includes Ag and Mo, another - Mn, Ba, Ni and Sr. Analysis of Ag and Mo distribution in the sediments and findings of molybdenite permitted conclusion that the enrichment of the sediments by these elements resulted from the edaphic washing of magmatic rocks which form Ag/Mo mineralization and are probably located on the northwestern slope of the Deryugin truogh.. The other geochemical group is most likely to be connected with hydrothermal barytic mineralization revealed in the northeastern part. Considering the type of Mn distribution in the bottom sediment columns, the supply of Mn is pulsating in character. It allows us to conclude that during the Holocene - Late Pleistocene, three cycles of hydrothermal activity were recognized for the Deryugin trough. The most intensive hydrothermal activity occurred during the Holocene.
I.V.Buchko
PGE distribution types in stratified ultrabasite-basite intrusions within the Stanovoy fold block system, an example from the Vesselkinsky massif
Considering the predominance of one or another platinoid, two types are estabilshed based on the investigations of PGE contents in stratified intrusive of the dunite-clinopyroxenite-gabbro formation, namely, the platinum (Pt) type and palladium (Pd) one. The first type is confined to layers with poor sulfide mineralization distributed in olivinite and characterized by the predominance of Pt over Pd. The second type spatially coincides with chrome-magnetite in ortho- and clinopyroxenites. The latter one is dominated by Pd.
E.L.Schkolnik, L.B.Kherschberg, M.M.Zadornov, O.V.Chudaev
The phosphorites of the Dalmorgeo guyot in the Magellan seamounts of the Pacific ocean
The paper describes a phosphate mineralization in the well studied Dalmorgeo guyot (the Magellan seamounts) in the Pacific ocean. A phosphate mineralization is connected with Cretaceous -Early Miocene sediments of a different consolidation grade, which cover the slopes and top of the guyot. During the reef stage of the guyot's evolution a nannoforaminiferal ooze filled pore sand holes. In the planktonic sediments phosphate occupies not only pores but cements as well. In general, phosphate mineralization was conditioned by high rates of planktonic organism sedimentation, and organic material transformation at the early diagenetic stage, when these organisms died out abruptly.