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Jolivet M.,French National Center for Scientific Research | Arzhannikov S.,Institute of the Earth Crust | Arzhannikova A.,Institute of the Earth Crust | Chauvet A.,Montpellier University | And 2 more authors.
Journal of Asian Earth Sciences | Year: 2013

The East Sayan ranges are a key area to understand the interactions between the transpressive deformation linked to the far-field effects of the India-Asia collision and the extension linked to the opening of the Baikal Rift System. The active deformation that affects this range is very recent (around 5Ma) but occurs in a very complex morphotectonic setting and the understanding of the Tertiary deformation relies entirely on a detailed knowledge of the pre-deformation situation. Using apatite fission track thermochronology, cosmogenic 10Be and morphological study on Tertiary lava flows we demonstrate that prior to the Oligocene the morphology of the East Sayan area was characterized by a wide, constantly rejuvenated erosion surface. Apatite fission track thermal modelling indicates that this surface started to form at least in Late Jurassic-Early Cretaceous (140-120Ma). The long-term exhumation rates (several tens of million years) derived from apatite fission track data (17.5m/Ma) and the short-term erosion rates (over a few hundred thousand years) derived from cosmogenic 10Be data (12-20m/Ma) are coherent implying a near constant mean erosion rate since Late Jurassic. This constant, slow erosion prevented the formation of a lateritic-kaolinic weathering crust on the planation surface. By Oligocene-early Miocene times a long wavelength uplift that remains to be explained, induced incision that created shallow valleys later filled by basaltic lava flows. Finally, the present short-wavelength topography initiated during the Pliocene. © 2011 Elsevier Ltd.

Jolivet M.,French National Center for Scientific Research | Arzhannikov S.,Institute of the Earth Crust | Chauvet A.,Montpellier University | Arzhannikova A.,Institute of the Earth Crust | And 3 more authors.
Gondwana Research | Year: 2013

The Baikal Rift System in southern Siberia is one of the main intracontinental extensional features on Earth. The rift system represents the northwestern boundary of the Amuria plate and in that respect can be considered as an evolving plate boundary. The Baikal Rift System has been widely studied both in terms of geology and geophysics and many models have been proposed for its formation and evolution. However, the age of the initiation of deformation and the mechanism driving this deformation are still largely debated. While major extension has occurred since the Late Miocene-Pliocene, the onset of extension seems older than the India-Asia collision, implying that several driving mechanisms may have acted together or in relay through time. In this work, we review the available data and models for deformation in an area encompassing the Baikal Rift System, the Sayan ranges to the west and the Transbaikal to the east. Using a synthesis of this data and our own field and mapping observations, we show that the Baikal Rift System, along with transpressional deformation in the Sayan ranges and transtension in the Transbaikal area, can be explained through major left-lateral strike-slip systems. The deformation is strongly controlled by inherited crustal and lithospheric structures, and is distributed over a wide area within the western Amuria plate that consequently cannot be considered as a rigid block. Such distributed deformation is likely to have a strong effect on the structure of the future continental margin if extension evolves towards the formation of oceanic crust. © 2012 International Association for Gondwana Research.

Arzhannikova A.,Institute of the Earth Crust | Arzhannikov S.,Institute of the Earth Crust | Jolivet M.,French National Center for Scientific Research | Vassallo R.,University of Savoy | Chauvet A.,Montpellier University
Journal of Asian Earth Sciences | Year: 2011

The South East Sayan area, W of the Lake Baikal is subjected to a very complex tectonic setting where the extensional stress field of the Baikal Rift System meets the compressional stress field generated by the India-Asia collision further south. Using satellite images, aerial photographs, SRTM DEM, field mapping of geomorphological structures, and published neotectonics and geological data we show that most of the relief in the SE Sayan initiated during Late Pliocene-Pleistocene through compressive reactivation of inherited structures. By Late Quaternary, clockwise rotation of the compressive field generated strike-slip faulting and local, secondary extension still within a general compressional stress field. We demonstrate that the formation of the small-scale extensional basins within the East Sayan range is not linked to general the extension in the Baikal Rift System nor to a possible asthenospheric plume acting at the base of the crust but rather to the rotation of small rigid tectonic blocks driven by the compression. © 2010 Elsevier Ltd.

Letnikova E.F.,RAS Institute of Geology and Mineralogy | Kuznetsov A.B.,Institute of Precambrian Geology and Geochronology | Vishnevskaya I.A.,RAS Institute of Geology and Mineralogy | Veshcheva S.V.,Institute of the Earth Crust | And 2 more authors.
Russian Geology and Geophysics | Year: 2013

Geochemical and isotopic (Sm-Nd and Sr) studies of deposits of the Baikal and Oselok Groups in the southern Siberian Craton and LA-ICP-MS U-Pb dating of detrital zircons show that they accumulated in passive continental-margin settings in the Vendian. The time limits of sedimentation were assessed on the basis of Sr chemostratigraphy of carbonate deposits of the Baikal Group and LA-ICP-MS U-Pb dating of detrital zircons in first-cycle terrigenous deposits of the Oselok Group. The main provenances for rocks of these groups were constant. These were rocks of the cover and basement of the Siberian Craton. Tuffite horizons in upper portions of the groups are the only sign of Late Vendian activation of this block, which is reflected in changes of geochemical indices of terrigenous rocks and their younger Sm-Nd model ages. © 2013.

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