Mass transfer between eastern Tien Shan and adjacent basins (central Asia): constraints on regional tectonics and topography

Abstract

Using depths and ages derived from isopachs, drill‐holes or cross‐sections, it is possible to reconstruct the space‐time depositional history of a sedimentary basin. Drill holes and cross‐sections give the local sedimentation history, while isopachs allow the definition of the spatial distribution of the sediments. Assuming several simple hypotheses, such as similarity of the strata and regional applicability of results derived from local analyses, one can reconstruct balanced maps of the solid (or grain) volumes, and hence the mass of sediments deposited during several time intervals since the Palaeogene. Applying this method to the Tarim and Dzungar basins (NW China), we estimate the total Cenozoic solid‐phase volume and mass of sediments stored to be 1358 ± 520 × 103 km3 (36.7 ± 14 × 1017 kg) and 172 ± 56 × 103 km3 (4.6 ± 1.5 × 1017 kg) respectively. The reconstruction also enables us to detect two main pulses in the sedimentation. The first, around 17 Ma, affected only the northern part of the Tarim Basin (also known as the Kucha or Kuche Depression) at the foot of the Tien Shan Mountains and supports the idea that the presently active shortening regime in that range started at that time. The second, 5 to 6 Ma, affected most of the depositional areas of the region and may have an even greater geographical extent. Assuming local isostasy, we estimate the volume of shortening induced by the rotation of the Tarim block relative to Siberia and stored in the range and adjacent basins to be between 1.15 × 106 and 4.23 × 106 km3. This corresponds to a clockwise rotation of between 2.5° and 8.7°. We use these results in two simple models of self‐similar growth of pyramidal topographies that approximately fit the eastern Tien Shan.

Paleo-erosion rates in Central Asia since 9Ma: A transient increase at the onset of Quaternary glaciations?

“…1). The large Pleistocene increase of sediment flux to the basins reported in previous studies (Métivier and Gaudemer, 1997;Zhang et al, 2001) is therefore a key observation.…”

“…The basal age of the conglomeratic 'Xiyu' formation found at each of these locations is indicated in bracket (see references in (Charreau et al, 2009b)). At the bottom, from left to right, the evolution of sediment flux to basins for the world (Zhang et al, 2001), and Central Asia (Métivier and Gaudemer, 1997) and the accumulation rates records derived from magnetostatigraphy arround the Tianshan (see references in (Charreau et al, 2009b)). The red box shows the location of attenuation lengths (g.cm -2 ) of spallogenic and muogenic productions; P e (t): the average spallation production rate for the whole drainage basin (in at.g -1 .yr -1 ); ε(t d ): the erosion rates on the drainage basin at the time of deposition (in cm.yr -1 ).…”

Thermo-Mechanical Models for Coupled Lithosphere-Surface Processes: Applications to Continental Convergence and Mountain Building Processes

“…1) because in this area, the rates of deformation and erosion have been well estimated from previous studies (Avouac et al, 1993: Metivier andGaudemer, 1997), and because this range has a relatively simple 2-D geometry. The Tien Shan is the largest and most active mountain range in central Asia.…”

Seismic Hazard in Tien Shan: Basement Structure Control Over the Deformation Induced by Indo-Eurasia Collision

“…However in most cases, it is safe to say that cooling initiated, seemingly in a somewhat poly-phased fashion, during the last 10 to 15 Ma. These cooling curves in the models might thus represent the timing of the denudation of the modern Tien Shan orogenic edifice and can be corroborated by several lines of independent geological evidence from such fields as sedimentology [Cobbold et al, 1994;Métivier & Gaudemer, 1997;Dill et al, 2007], magneto-stratigraphy [Sun et al, 2004;Charreau et al, 2005;Huang et al, 2006;Ji et al, 2008], geomorphology and structure [Tibaldi et al, 1997;Yin et al, 1998;Burbank et al, 1999;Abdrakhmatov et al, 2001;Thompson et al, 2002;Buslov et al, 2003;Fu et al, 2003;Hubert-Ferrari et al, 2007;Oskin & Burbank, 2007], geophysics [Trapeznikov et al, 1997;Bielinski et al, 2003;Rybin et al, 2004;, geodesy [Abdrakhmatov et al, 1996;Reigber et al, 2001;Vinnik et al, 2004;Tychkov et al, 2008], and other geochronological studies [Sobel & Dumitru, 1997;Bullen et al, 2001;Sobel et al, 2006;De Grave et al, 2007a;Heermance et al, 2007]. We should caution the reader that this Late Cenozoic feature is mainly obtained by modelling the AFT data [Laslett et al, 1987;Ketcham et al, 2000].…”

“…Given the ages, the specific low-T-sensitivity of the various thermochronologic methods applied, and the punctuated character, we interpret the Jurassic-Cretaceous Kyrgyz Tien Shan basement cooling as exhumation of this basement due to denudation of the overlying bedrock. The denudation and erosion can be associated with a phase of tectonic reactivation of the Tien Shan orogen and rejuvenated mountain building [Graham et al, 1993;Cobbold et al, 1994;Allen & Vincent, 1997;Métivier & Gaudemer, 1997;Hendrix, 2000;Li et al, 2004]. This Mesozoic tectonic activity and the resulting sediments are expressed in the field e.g.…”