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Russian Geology and Geophysics

2008 year, number 1


V.V. Khomentovsky, K.E. Nagovitsin, A.A. Postnikov
Institute of Petroleum Geology and Geophysics, Siberian Branch of the RAS, 3 prosp. Akad. Koptuyga, Novosibirsk, 630090, Russia
Keywords: Mayanian; Kerpylian; Lakhandinian; Baikalian; microfossils; stromatolites; geochronology; geodynamics; event boundaries
Pages: 1-22

Abstract >>
The Mayanian (1100-850 Ma) is an all-Siberian stratigraphic subdivision of the Neoproterozoic distinguished on the basis of generalized geological and paleontological data for the Maya Group in the southeast of the Siberian craton and for its counterparts in other structure-facies areas (SFA). The Mayanian deposits in all principally different structures of every SFA, such as intracratonic depressions, pericratonic troughs, and marginal parts of blocks with oceanic crust, were incorporated into the craton in the Vendian. It is separated from the surrounding stratigraphic divisions, Baikalian and Aimchanian, by distinct tectonic boundaries coinciding in time with the formation and starting breakup of the supercontinent Rodinia, i.e., with global events. In the adjacent parts of the platform they were reflected in erosion and considerable gaps in sedimentation. These events are well-expressed where they occurred under intense contraction or, on the contrary, are veiled where extension was predominant.
The boundary between the Kerpylian and Lakhandinian, subdivisions of the Mayanian, is not bearing on important events and is hardly traceable throughout the region. Therefore, the base of the Kerpylian is preferable to be taken as the lower boundary of the Upper Riphean. There are attempts to establish this boundary, as it is made for the Phanerozoic, from paleontological data in compositionally similar deposits. These attempts, however, fail in matching this boundary with the base of the Lakhandinian. Distinctive transitions in communities of microfossils and stromatolites appear to be linked to the Mayanian-Baikalian and, undoubtedly, Middle Riphean-Aimchanian boundaries. In the Lakhandinian, on the contrary, the changes that appeared in the Kerpylian only tend to continue. Some taxa typical of the Lakhandinian appear as early as the Kerpylian. In the Lakhandinian their amount gradually increases upsection, until the top of this division. Thus, it is reasonable to start the Upper Riphean with the lower boundary of the Mayanian.
All the main subdivisions of the Siberian Neoproterozoic - Mayanian, Baikalian, and Vendian - are linked to the most important stages of development of this vast and structurally heterogeneous territory. Each of the above-mentioned stratons can be divided, according to historico-geological and paleontological data, into two or three independent interregional subdivisions. Thus, the stratigraphic scheme of the Neoproterozoic of Siberia seems to be promising for the general scale of this period of the Late Precambrian.


Li Rongxia,b, Li Youzhua,b
a Key Laboratory of West Mineral Resource and Geology Engineering, Education Ministry of China,
Chang'an University, 126 Yanta Road, Xian, 710054, China
b School of Earth Science and Resource, Chang'an University,126 Yanta Road, Xian, 710054, China
Keywords: Tectonic evolution, petroleum potential, stratigraphy, Ordos Basin, China
Pages: 23-27

Abstract >>
The western half of the Ordos Basin lies in the north of Central China, on the western margin of the North Chinese Platform. In the southwest and south it borders the Qilian and Qinling folded systems. Their frontal northeastern flank is thrust over the Paleozoic nappe of the Ordos Basin and consists of a series of large parallel linear folds separated by thrusts. The basement of the basin is made up of deformed metamorphic rocks of tentatively Late Proterozoic age. Carbonate and terrigenous intracratonic facies accumulated on the Ordos block from Early Cambrian through Middle Ordovician. From Middle Ordovician through Middle Carboniferous, the western edge of the block was uplifted as a land as a result of Caledonian tectonic movement and underwent denudation for about 150 Myr. In the Late Paleozoic, a series of coal-bearing formations was deposited. In the Triassic, the Ordos Basin became filled with fluviolacustrine delta facies. Thrusts and folds on the southwestern margin of the basin formed in the Mesozoic and were intensified by Himalayan tectonic movements.


N.I. Akulov, B.P. Agafonov†, M.N. Rubtsova
Institute of the Earth's Crust, Siberian Branch of the RAS, 128 ul. Lermontova, Irkutsk, 664033, Russia
Keywords: Quaternary glaciation; morainic deposits; fluvioglacial formations; «watershed pebbles»; Lake Baikal; western Baikal area
Pages: 28-39

Abstract >>
Results of the activity of Quaternary glaciations in the western Baikal area are considered based on new factual material. Also, the problem of the formation of

EARLY RESPONSE OF CONTINENTAL ASIA TO PLEISTOCENE CLIMATE CYCLES ( retuned orbital chronologies for Baikal, marine, and ice core records )

M.A. Phedorin a, b , E.L. Goldberg a, b
a Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the RAS, 3 prosp. Koptyuga, Novosibirsk, 630090, Russia
b Limnological Institute, Siberian Branch of the RAS, 3 ul. Ulanbatorskaya, 664033, Irkutsk, Russia
Keywords: Pleistocene paleoclimate records; orbital climate cycles; Baikal records; 100-kyr cycle
Pages: 40-45

Abstract >>
Assuming orbital modulation of Pleistocene climate cycles, we have generated a new time scale for the Asian geochemical limnic record in the BDP-96-2 Baikal and the KDP-01 Hovsgol cores and updated the chronologies for the global marine δ18O and Vostok ice-gas records. The time scales were obtained by orbital tuning with the assumption of arbitrary but time invariable amplitudes and phase lags of the orbital parameters and responses.
The retuned chronologies highlighted the cycles of eccentricity (100 kyr), obliquity (41 kyr), and precession (23 and 19 kyr), but the combined 70- and 30-kyr cycles became less prominent in the continental (Baikal) record though persisted in the global data (Vostok δD). The residual 70- and 30-kyr harmonics more likely result from errors in the untuned chronology for the Baikal record but are rather due to nonlinearity in the climate response.
We investigated the leads and lags of orbital climate signals with a special focus on the 100-kyr cycle. The phases of precession, obliquity, and eccentricity cycles, compared among the records, showed the lead of the continent. The Baikal geochemical signal at the 100-kyr band led the global glacial and greenhouse CH4 responses and was almost synchronous with the earliest responding polar temperature signal. The reported results characterize the continent as a system highly responsive to eccentricity variations but do not contradict alternative hypotheses for the origin of the 100-kyr cycle in the Earth's climate history.


I.N. Malikova a , M.T. Ustinov b , G.N. Anoshin a , Zh.O. Badmaeva a , Yu.I. Malikov a
a Institute of Geology and Mineralogy, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
b Institute of Soil Sciences and Agrochemistry, Siberian Branch of the RAS, 18 ul. Sovetskaya, Novosibirsk, 630099, Russia
Keywords: Mercury; catchment area of Lake Bol'shoe Yarovoe; soils; plants; waste
Pages: 46-51

Abstract >>
We examined mercury distribution in soils and plants of the catchment area of Lake Bol'shoe Yarovoe with the Altaikhimprom chemical industrial complex situated on its shore. Data on mercury contents show a considerable mercury flow into the environment, though the industrial complex and its waste do not pose serious threat. The revealed pollution in the immediate vicinity of the industrial complex, including that due to atmospheric transport, as well as the elevated content of mercury in hydrochloric and alkaline extracts suggest its intense migration from the waste. Therefore, it is necessary to make up an inventory of the industrial-complex waste and perform a detailed study of the lake ecosystem as a model unit.


S.V. Astafurova, E.V. Shilkoa, V.V. Ruzhichb, S.G. Psakhiea
a Institute of Strength Physics and Materials Science, Siberian Branch of the RAS, 2/1, prosp. Akademichesky, Tomsk, 634021, Russia
b Institute of the Earth's Crust, Siberian Branch of the RAS, 128, ul. Lermontova, Irkutsk, 664033, Russia
Keywords: Faulted crust; interface; dynamic loading; response; slip; stress
Pages: 52-58

Abstract >>
The effect of local stress on the interface response to dynamic loading in faulted crust has been studied through MCA (movable cell automata) simulation. Knowing the strain response of a fault block boundary to test impacts, one can estimate the proximity of the fault to critical stress that allows an unstable slip. The computing results are consistent with data of field experiments in fault fragments (vibration, water injection, explosions). The reported analysis makes the basis for a new approach to estimating stress and strain in active faults.


V.V. Bakhterev
Institute of Geophysics, Ural Branch of the RAS, 100, ul. Amundsena, Ekaterinburg, 620016, Russia
Keywords: Serpentinization of ultramafics; electrical resistance; high temperature; activation energy
Pages: 59-63

Abstract >>
Electrical resistance measurements, thin-section, chemical, thermal differential, and thermal gravity analyses have been applied to study samples of chromite and the host serpentinite from the Podenny and Kurman deposits in the Alapaevsk ophiolite and from the Piany Bor and southern deposits in the Klyuchevskoi ophiolite. Samples from the four sites exhibit similar patterns of activation energy (E0) vs. resistance coefficient (log R0). The E0-log R0 points of samples collected away from ore fields align along a straight line corresponding to the log R 0 = a - bE0 relationship typical of nonmineralized rocks, with the a and b coefficients as in alpine ultramafics. The samples of mineralized rocks depart from the basic line, the departure increasing as they approach the orebody. Though having similar patterns, the E0-log R0 fields of the samples from different sites show no overlap. The revealed features may be useful as implicit diagnostic criteria for ophiolite-hosted chromite mineralization.


A.G. Konstantinov
Institute of Petroleum Geology and Geophysics, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
Keywords: Triassic; Ladinian Stage; Carnian Stage; ammonoids; biostratigraphy; zonal scales; correlation
Pages: 64-71

Abstract >>
Various opinions on the position of the Middle/Upper Triassic boundary have been concisely reviewed. The lower boundary of the Carnian Stage is accepted at the base of the Trachyceras aon Zone. The recentmost data on biostratigraphy of boundary beds of the Ladinian and Carnian Stages of the Southern Alps, Himalayas, British Columbia, northeastern Asia, Svalbard, and Arctic Canada have been considered and critically analyzed. Using sections of British Columbia with mixed Boreal and Tethyan fauna of Ammonoidea, we compared biostratigraphic schemes of the Middle/Upper Triassic boundary interval of the Boreal and Tethyan regions. On the basis of correlations and paleontological data, the lower boundary of the Carnian Stage in Northeastern Asia is suggested to be drawn at the base of the ammonoid