Geologiya I Geofizika, 2002, V 43, N 6, June.

STRATIGRAPHY AND PALEONTOLOGY

MAJOR CAMBRIAN BIOTIC BOUNDARIES IN THE NORTHERN SIBERIAN PLATFORM 
I. V. Korovnikov, A. V. Fedoseev, and D. P. Sipin
489

     We have characterized complexes of the guide faunal groups (small-shelled 
fauna, archaeocyathids, trilobites, and brachiopods) and followed their 
stratigraphic and lateral distribution in the Cambrian deposits of the northern 
Siberian platform. Eleven boundaries, where these complexes undergo major biotic 
transformations, have been established. The boundaries are compared with those 
characterized in other studies, as well as with the carbon isotope datings from 
different sections of the Siberian Platform. Some of the boundaries established 
in this study correlate well with global biotic events and with the extrema of 
carbon isotope ratio curves. The examples include Boundary 1, the lower boundary 
of the Tommotian stage; Boundary 3, the lower boundary of the Atdabanian stage; 
Boundary 5, the lower boundary of the Botomian stage; and Boundaries 7 and 8 
marking the transition from the Lower to Middle Cambrian in the Siberian 
Platform. Additionally, Boundary 9 is an almost universally present lower 
boundary of the Triplagnostus gibbus Zone of the Amgan stage.
      Cambrian, trilobites, brachiopods, archaeocyathids, small-shelled 
fauna, biotic boundaries, northern Siberian Platform

ORDOVICIAN SILICEOUS AND SILICEOUS-BASALT FORMATIONS OF KAZAKHSTAN 
I. F. Nikitin
508

     Data on the stratigraphy of siliceous-basalt deposits of Ordovician age 
from Central Kazakhstan have been summarized. The age, succession, and 
correlation between these deposits are refined. Geological dating and 
correlation are based chiefly on conodonts and, to a lesser extent, graptolites. 
It is established that the age of these formations in the west and east of 
Central Kazakhstan is constrained by the Early to Middle Ordovician and in the 
interior structures (Zhungaria-Balkhash zone) it spans the entire Ordovician 
and, possibly, early Silurian. The siliceous and siliceous-terrigene deposits of 
Ordovician age are the water-deepest hemipelagic and pelagic sediments, and 
their accumulation corresponds to the maximum of Arenigian-to-Llanvirnian 
transgression. The reported paleogeographic and paleotectonic data are in 
agreement with the existing paleotectonic reconstructions according to which 
Central Kazakhstan was a marginal basin of the West Pacific type during the 
Ordovician.
     Ordovician, stratigraphy, conodonts, siliceous sediments, basalts, 
Kazakhstan

PETROLOGY, GEOCHEMISTRY, AND MINERALOGY

GEODYNAMICS OF MESO-CENOZOIC VOLCANIC COMPLEXES OF VALAGA RIDGE, KAMCHATKA
 (evolution from spreading to within-plate and island-arc magmatism or accretion of exotic terranes?) 
Yu. M. Puzankov
524
     The paper addresses a comparative geochemical study of volcanic complexes 
that evolved in the Asia/Pacific transition zone from the Late Cenonian to 
Present.
     Chemical compositions were analyzed in 111 representative samples of 
Cenozoic rocks from the eastern side of the Valaga Ridge (Eastern Kamchatka) on 
continuation of the Emperor's Ridge axis, in the region of hotspot volcanism; 
the dataset also includes 39 additional precise analyses published earlier by 
Puzankov et al. Trace elements were determined by INAA, XRF, AAS, LL methods and 
gamma spectrometry developed in UIGGM, Novosibirsk.
     The magmatic complexes of Eastern Kamchatka and the surrounding regions 
were interpreted on the basis of rock chemistry as formed in spreading, island-
arc, and transitional geodynamic environments. Broad occurrence of transitional 
igneous complexes brings together the Meso-Cenozoic volcanic system including 
magmatic chambers at different depths. Accretion postdates the magmatic 
evolution. According to paleontological and K-Ar age constraints, the Eastern 
Kamchatka hotspot has not moved much for 40 Ma (from the Eocene to the 
Pleistocene), though the total extent of alkaline and subalkaline rocks attains 
200-300 km.
     Geochemistry, igneous rocks, Meso-Cenozoic, Eastern Kamchatka

Ar AND He ISOTOPES IN THE DOVYRA MAFIC-ULTRAMAFIC INTRUSION 
E. G. Konnikov, E. M. Prasolov, I. V. Tokarev, E. V. Kislov, and D. A. Orsoev
539

     The paper presents results of Ar and He isotopic studies in rocks and 
sulfide ores of the Late Precambrian Dovyra dunite-troctolite layered intrusion 
(Northern Baikal region). The intrusion shows 3He/4He and 
40Ar/36Ar ratios similar to other basic intrusions in the 
continental crust, and the gases in fluid inclusions contain a significant 
crustal component. The lowest 3He/4He and 40Ar/36Ar 
ratios, similar to those typical of fluids in the continental crust, were found 
in sulfide ores of the intrusion, which indicates involvement of crustal fluids 
in magmatic mineralization of the intrusion.
     Isotopes, helium, argon, fluids, contamination, layered intrusions

GEOLOGY OF OIL AND GAS

STRUCTURALLY CONTROLLED OCCURRENCES OF BATHOMIAN RESERVOIR RICKS WITHIN THE TAZ-NADYM INTERFLUVE 
A. A. Kartashov
549
     Analysis of borehole testing data shows that the large areas where 
reservoir rocks exist within the Bathonian permeable complex gravitate to 
certain structural features. These features have been analyzed with respect to 
inflow of hydrocarbons. According to petroleum potential, the structural 
settings were classified as highly promising, promising, and nonpromising.

     Reservoir zones, structural setting, Bathonian reservoir, petroleum 
potential, West Siberia, Taz-Nadym interfluve

GEOPHYSICS

ONGOING VERTICAL MOVEMENTS IN THE ALTAI-SAYAN PROVINCE AND THEIR 
RELATIONSHIP TO NEOTECTONICS AND SEISMICITY 
P. P. Kolmogorova and V. G. Kolmogorov
563

     Geodetic surveys, especially repeated leveling carried out for the first 
time in the territory of the Altai-Sayan province through the recent decades, 
have yielded a cartographic model of ongoing vertical movements of the Earth's 
surface. The numerical parameters of the model were obtained from the equation 
of leveling network consisting of closed polygons and isolated lines, about 
10,000 km of total length.
     The model reflects regional-scale regular distribution of the rates of 
vertical movements. According to this regularity, the Biya-Katun', Barnaul, and 
Mras blocks are stable, while the background ongoing vertical movements in the 
province are regional-scale doming south of the Barnaul-Biya-Katun' stable block 
and subsidence of the province's northwestern part north of the stable zone. 
Doming is accompanied by local but often considerable subsidence which provides 
further deepening of intermontane depressions.
     Analysis of the relationship between active and neotectonic structures 
revealed regions in which the ongoing movements are conformal to the evolution 
trends of the earlier neotectonic stage and those in which they are different. 
The obtained model of ongoing vertical movements of the Earth's surface was also 
used to detect zones of active faulting.

     Ongoing vertical movements, neotectonic movements, correlation 
analysis, Altai-Sayan folded area