Time filter

Source Type

Safonova I.,RAS Institute of Geology and Mineralogy | Santosh M.,Kochi University | Santosh M.,China University of Geosciences
Gondwana Research | Year: 2014

The accretionary complexes of Central and East Asia (Russia, Kazakhstan, Kyrgyzstan, Tajikistan, Mongolia, and China) and the Western Pacific (China, Japan, Russia) preserve valuable records of ocean plate stratigraphy (OPS). From a comprehensive synthesis of the nature of occurrence, geochemical characteristics and geochronological features of the oceanic island basalts (OIB) and ophiolite units in the complexes, we track extensive plume-related magmatism in the Paleo-Asian and Paleo-Pacific Oceans. We address the question of continuous versus episodic intraplate magmatism and its contribution to continental growth. An evaluation of the processes of subduction erosion and accretion illustrates continental growth at the active margins of the Siberian, Kazakhstan, Tarim and North China blocks, the collision of which led to the construction of the Central Asian Orogenic Belt (CAOB). Most of the OIB-bearing OPS units of the CAOB and the Western Pacific formed in relation to two superplumes: the Asian (Late Neoproterozoic) and the Pacific (Cretaceous), with a continuing hot mantle upwelling in the Pacific region that contributes to the formation of modern OIBs. Our study provides further insights into the processes of continental construction because the accreted seamounts play an important role in the growth of convergent margins and enhance the accumulation of fore-arc sediments. © 2012 International Association for Gondwana Research.

Kuzmin Y.V.,RAS Institute of Geology and Mineralogy
Radiocarbon | Year: 2012

The recent progress in radiocarbon dating of the prehistoric cultural complexes in the Russian Far East is discussed against the background of ancient chronologies for greater East Asia. Since 1997, the wide use of accelerator mass spectrometry (AMS) radiocarbon dating along with the continuation of conventional dating has allowed us to establish the age of several key Paleolithic, Neolithic, and Paleometal sites. It has also contributed to advancing a deeper understanding of the timing for the beginning of pottery production, maritime adaptation, and agriculture, and several other important issues in prehistoric chronology for the studied region. Reservoir age correction values for the Japan and Okhotsk seas are now used to adjust the age for samples of marine origin. Some of the cultural-chronological models for prehistoric far eastern Russian complexes put forward in the last 10 yr lack a solid basis, and are critically evaluated herein. © 2012 by the Arizona Board of Regents on behalf of the University of Arizona.

The current evidence for date and environmental preferences of the extinction of two middle-late Pleistocene megafaunal species, the woolly mammoth (Mammuthus primigenius Blum.) and woolly rhinoceros (Coelodonta antiquitatis Blum.), is presented in this review. It is suggested that extinction of these large herbivores in Eurasia was closely related to landscape changes near the Pleistocene-Holocene boundary (c. 12 000-9000 uncalibrated radiocarbon years ago, yr BP), mainly involving the widespread forest formations in the temperate and arctic regions of northern Eurasia and the loss of grasslands crucial to the existence of woolly mammoth and rhinoceros. However, some woolly mammoth populations survived well into the Holocene (up to c. 3700 yr BP), showing that the process of final extinction was fairly complex, with delays in some regions of up to several millennia. The possible role of Palaeolithic humans in the extinction of Late Pleistocene megafauna is also considered. © 2009 The Authors, Journal compilation © 2009 The Boreas Collegium.

Kuzmin Y.V.,RAS Institute of Geology and Mineralogy
Radiocarbon | Year: 2010

The chronometry of the origin of pottery in East Asia can give some insights to the question: did environmental changes trigger and/or accelerate innovations such as pottery-making, maritime adaptation, and agriculture? Recent results show that pottery emerged in 3 regions of East Asia: south China (up to ~14,800 BP), the Japanese Islands (about 13,800- 13,500 BP), and the Russian Far East (~13,300 BP). The earliest pottery in the Old World preceded the Bølling-Allerød warm period (about 13,000-11,500 BP). Thus, the relationship between climate and pottery origin was not "linear." It seems that the combination of environmental changes and the necessity to process freshwater fish and mollusks and terrestrial plants (including acorns and nuts) resulted in the introduction of pottery-making in East Asia. An important feature is the quite nonuniform nature of the Neolithization process in the eastern part of Asia, where often in 2 neighboring regions pottery appeared at very different times: approximately 15,000-14,000 BP in south China and ~4000 BP in mainland Southeast Asia. Thus, the kind of eternal question like "What caused what?" still stands in terms of what were the driving forces for the emergence of pottery in East Asia and worldwide. © 2010 by the Arizona Board of Regents on behalf of the University of Arizona.

Kuzmin Y.V.,RAS Institute of Geology and Mineralogy
Radiocarbon | Year: 2013

Data on the emergence of pottery and agriculture in Eurasia were analyzed from the view of their spatiotemporal relationship. It was found that there are 2 major types of association between pottery and agriculture: 1) East Asian, with pottery as the main criterion of the Neolithization; and 2) Levantine, with agriculture as the phenomenon most closely related to the emergence of the Neolithic. Some regions of Eurasia have intermediate characteristics. The concept of a single area for pottery origin in eastern Eurasia and its subsequent spread to the west, still used by some scholars, is the revival of the old diffusionist paradigm and does not seem to advance the analysis of the Neolithization process. If the wheat/barley agriculture definitely originated in the Levantine "core" and spread toward Anatolia and central/western Europe, it is impossible to apply the same approach to pottery. The latest developments in chronology of the earliest ceramics in China, one of the key regions in the world in terms of the origin of pottery-making, are critically evaluated. © 2013 by the Arizona Board of Regents on behalf of the University of Arizona.

Mikhno A.O.,RAS Institute of Geology and Mineralogy | Korsakov A.V.,RAS Institute of Geology and Mineralogy
Gondwana Research | Year: 2013

Despite extensive studies of calc-silicate rocks of the Kokchetav massif, there is no satisfactory explanation of the origin of potassium-bearing clinopyroxene in alkali poor metamorphic rocks. In this paper we report the finding of potassium-bearing clinopyroxene with prograde zonation (K2O increases from core to rim) from diamond-grade, but diamond-free UHP calc-silicate rocks of the Kokchetav massif. We believe that the crystallization of potassium-bearing clinopyroxene started on the prograde stage and slightly prior to the peak of UHP metamorphism. Thus, prograde metamorphic history is only traceable in diamond-free UHP calc-silicate rocks, while in diamond-bearing UHPM rocks it is completely reset. Fluid and polyphase solid inclusions, originally representing melt inclusions, occur in the core of potassium-bearing clinopyroxene and imply that melt and fluid may coexist in calc-silicate rocks even at 1000-1100°C and 6-7GPa. © 2012 International Association for Gondwana Research.

Novikov I.S.,RAS Institute of Geology and Mineralogy
Russian Geology and Geophysics | Year: 2013

The Junggar basin contains an almost continuous section of Late Carboniferous-Quaternary terrigenous sedimentary rocks. The maximum thicknesses of the stratigraphic units constituting the basin cover make up a total of ~. 23 km, and the basement under the deepest part of the basin is localized at a depth of ~. 18 km. Both the folded framing and the basin edges have undergone uplifting and erosion during recent activity. These processes have exposed all the structural stages of the basin cover. Considering the completeness and detailed stratigraphic division of the section, we can determine the exact geologic age of intense mountain growth and erosion periods as well as estimate the age of orogenic periods by interpolating the stratigraphic ages. During the Permian orogeny, which included two stages (255-265 and 275-290 Ma), the Junggar, Zaisan, and Turpan-Hami basins made up a whole. During the Triassic orogeny (210-230 Ma), the Junggar and Turpan-Hami basins became completely isolated from each other. During the Jurassic orogeny (135-145 and 160-200 Ma), the sedimentation took place within similar boundaries but over a smaller area. During the Cretaceous orogeny (65-85 and 125-135 Ma), the mountain structures formed mainly at the southern boundaries of the basin and along the Karamaili-Saur line. The Junggar and Zaisan basins were separated at that time. The Early and Middle Paleogene were characterized by relative tectonic quiescence. The fifth orogenic stage began in the Oligocene. The recent activity consists of two main stages: Oligocene (23-33 Ma) and Neogene-Quaternary (1.2-7.6 Ma to the present). © 2013 Elsevier B.V.

Dobretsov N.L.,RAS Institute of Geology and Mineralogy
Russian Geology and Geophysics | Year: 2010

The paper is a synthesis of models for basic geodynamic processes (spreading, subduction transient into collision, mantle plumes) in relation with the Earth's evolution and regularly changing geodynamic parameters. The main trends and milestones of this evolution record irreversible cooling of the Earth's interior, oxidation of the surface, and periodic changes in geodynamic processes. The periodicity consists of cycles of three characteristic sizes, namely 700-800 Myr global cycles, 120, 90, and 30 Myr smaller cycles, and short-period millennial to decadal oscillations controlled by changing Earth's orbital parameters and, possibly, also by other extraterrestrial factors. Major events and estimates of mantle and surface temperatures, heat flow, viscosity, and the respective regimes of convection and plume magmatism have been reported for the largest periods of the Earth's history: Hadean (4.6-3.9 Ga), Early Archean (3.9-3.3 Ga), Late Archean (3.3-2.6 Ga), Early Proterozoic (2.6-1.9 Ga), Middle Proterozoic (1.9-1.1 Ga), Neoproterozoic (1.1-0.6 Ga), and Phanerozoic with two substages of 0.6-0.3 and 0.3-0 Ga. Current geodynamics is discussed with reference to models of spreading, subduction, and plume activity. Spreading is considered in terms of double-layered mantle convection, with focus on processes in the vicinity of mid-ocean ridges. The problem of mafic melt migration through the upper mantle beneath spreading ridges is treated qualitatively. Main emphasis is placed on models of melting, comparison of experimental and observed melt compositions, and their variations in periods of magmatic activity (about 100 kyr long) and quiescence. The extent and ways of interaction of fluids and melts rising from subduction zones with the ambient mantle remain the most controversial. Plume magmatism is described with a "gas torch" model of thermochemical plumes generated at the core-mantle boundary due to local chemical doping with volatiles (H2, CH2, KH, etc.) which are released from the metallic outer core, become oxidized in the lower mantle, and decrease the melting point of the latter. The concluding section concerns periodicities in endogenous processes and their surface consequences, including the related biospheric evolution. © 2010.

Buslov M.M.,RAS Institute of Geology and Mineralogy
Russian Geology and Geophysics | Year: 2011

The following structural elements have been recognized to constitute the tectonic demarcation of Central Asian Foldbelt: (1) The Kazakhstan-Baikal composite continent, its basement formed in Vendian-Cambrian as a result of Paleoasian oceanic crust, along with Precambrian microcontinents and Gondwana-type terranes, subduction beneath the southeastern margin of the Siberian continent (western margin in present-day coordinates). The subduction and subsequent collision of microcontinents and terranes with the Kazakhstan-Tuva-Mongolia island arc led to crustal consolidation and formation of the composite-continent basement. In Late Cambrian and Early Ordovician, this continent was separated from Siberia by the Ob'-Zaisan ocean basin. (2) The Vendian and Paleozoic Siberian continental margin complexes comprising the Vendian-Cambrian Kuznetsk-Altai island arc and the rock complexes of Ordovician-Early Devonian passive margin and Devonian to Early Carboniferous active margin. Fragments of Vendian-Early Cambrian oceanic crust represented by ophiolite and paleo-oceanic mounds dominate in the accretionary wedges of island arc. The Gondwana-type continental blocks are absent in western Siberian continental margin complexes and supposedly formed at the convergent boundary of a different ocean, probably, Paleopacific. (3) The Middle-Late Paleozoic Charysh-Terekta-Ulagan-Sayan suture-shear zone separating the continental margin complexes of Siberia and Kazakhstan-Baikal. It is composed of fragments of Cambrian and Early Ordovician oceanic crust of the Ob'-Zaisan basin, Ordovician blueschists and Cambrian-Ordovician turbidites, and Middle Paleozoic metamorphic rocks of shear zones. In the suture zone, the Kazakhstan-Baikal continental masses moved westward along the southeastern margin of Siberia. In Late Devonian and Early Carboniferous, the continents amalgamated to form the North Asian continent. (4) The Late Paleozoic strike-slip faults forming an orogenic collage of terranes, which resulted from Late Devonian to Early Carboniferous collision between Kazakhstan-Baikal and Siberian continents and Late Carboniferous to Permian and Late Permian to Early Triassic collisions between East European Craton and North Asian continent. As a result, the Vendian to Middle Paleozoic accretion-collisional continental margins of Siberia and the entire Kazakhstan-Baikal composite continent became fragmented by large-amplitude (up to a few thousand kilometers) strike-slip faults and conjugate thrusts into several strike-slip terranes, which mixed with each other and thus disrupted the original geodynamic, tectonic, and paleogeographic demarcation. © 2011.

Dobretsov N.L.,RAS Institute of Geology and Mineralogy
Russian Geology and Geophysics | Year: 2011

There were two key stages in the history of Paleozoids that formed in the place of the Paleoasian ocean, one in the Cambrian-Ordovician and the other in the Permian-Triassic. Both time spans were characterized by a combination of similar geodynamic, magmatic, and geomagnetic events: closure and opening of oceanic basins, intense plume magmatism associated with Earth's core cooling, and absence of geomagnetic reversals (superchrons). Three superchrons about 490-460, 260-300, and 124-86 Ma correlate with major events of plume magmatism. Plume reconstructions have to be updated for the period 490-460 Ma, which corresponded to the third superchron and was marked by ocean opening. The previous superplume, about 800-740 Ma, requires further justification but fits the global periodicity with 240 Ma major cycles and smaller ones of 120 (or also 30) Ma.In the Late Cambrian-Ordovician, large-scale accretion and collision events acted, in similar tectonic settings, upon the vast territory that currently extends from the Polar Urals to Lake Baikal (and was times larger in the past). As a result, Gondwanian microcontinents (Kokchetav, Altai-Mongolia, Tuva-Mongolia, etc.) and island arcs joined into the Kazakhstan-Tuva-Mongolia system. The formation of the Late Cambrian-Ordovician orogen in Central Asia was synchronous with opening of the Ural, Ob-Zaisan, Turkestan, and Paleotethys oceans. The plume pulses (520-500 and 490-460 Ma) may have been responsible for opening of new oceans, accelerated amalgamation of terranes, and synchronicity in geodynamic events from the Urals to Transbaikalia. © 2011.

Loading RAS Institute of Geology and Mineralogy collaborators
Loading RAS Institute of Geology and Mineralogy collaborators