The first radiocarbon-dated pollen record from the Mamakan section is presented. This record has become the basis for the reconstruction of the vegetation and climate of the Middle Holocene in the Mamakan archaeological area, where a number of well-known Siberian archaeological sites of the Late Mesolithic–Middle Bronze period are located. Reconstructions suggest that sparse spruce and larch stands dominated in the area between 6450 and 6150 cal BP. Later, from 6150 to 4700 cal BP, Scots pine began to spread in a warmer climate than before, following the general trend of its expansion in the southern part of Eastern Siberia. A cooler climate than previously with increased soil and air humidity occurred in the Mamakan region from 4700 to 3840 cal BP, causing the regional expansion of Siberian pine. The time interval from 3840 to 3600 cal BP was characterized by the significant development of pine, spruce, and larch forests. On the basis of the age model, we assume that, in the lower reaches of the Vitim River and, probably, in other mountain regions north of Lake Baikal, Scots pine spread about 600 years later than in the Cis-Baikal region and east of the lake. This transition from dark coniferous-taiga to light coniferous-taiga with a predomination of Scots pine signifies the most fundamental change in vegetation of the Baikal region in the Holocene. This is often discussed as one of the possible causes of the Middle Neolithic cultural hiatus (6660–6060 cal BP), which has been documented in the archaeological records from different parts of this vast region. Reconstruction of vegetation in the Mamakan region suggests that the territory of the Nizhnii Vitim River has been favorable for humans during most of the hiatus recorded in the Cis-Baikal area and may have been considered as a refuge for populations of hunter-gatherers in the Middle Neolithic.
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1.
Numerical viscoelastic modelling by the spectral Laguerre method 总被引：1，自引：0，他引：1
Seismic wave propagation in a viscoelastic media can be described by a system of integro-differential equations. The solution of such equations requires special methods when using finite-difference techniques in the time domain. In the frequency domain, the integral terms are represented by complex elastic parameters. This paper presents an efficient algorithm for viscoelastic modelling based on the integral Laguerre transform for the approximation of temporal derivatives and for the calculation of convolution integrals. For the calculation of spatial derivatives, it is possible to use various methods: finite-difference and finite-element techniques, spectral and pseudo-spectral methods. We then obtain a system of algebraic equations with a matrix independent of the parameter m , i.e. the degree of the Laguerre polynomials. In this case, only the right-hand side of the system has recurrent dependence on the parameter m , which is an analogue of the temporal frequency in the frequency domain. The obtained system with a large number of right-hand sides can be solved using fast methods, where the matrix is transformed only once, as opposed to the frequency-domain approach, when the matrix is transformed for each temporal frequency. 相似文献
2.
Vishnevsky D. M. Kolyukhin D. R. Lisitsa V. V. Protasov M. I. Reshetova G. V. Tcheverda V. A. Qu D. Tveranger J. 《Doklady Earth Sciences》2017,473(2):477-481
Doklady Earth Sciences - This paper addresses seismic imaging of fault zones and analysis of the seismic data with the use of the fault facies model developed at Uni Research CIPR. Simulated and... 相似文献
3.
Bezrukova E. V. Reshetova S. A. Volchatova E. V. Kuzmin M. I. 《Doklady Earth Sciences》2022,506(1):687-692
Doklady Earth Sciences - The Central part of the Oka Plateau lying in the East Sayan Mountains is still a poorly studied area of southern Siberia as regards its paleogeography. This gap can be... 相似文献
4.
This paper presents a new approach to a local time-space grid refinement for a staggered-grid finite-difference simulation
of waves. The approach is based on approximation of a wave equation at the interface where two grids are coupled. As no interpolation
or projection techniques are used, the finite-difference scheme preserves second order of convergence. We have proved that
this approach is low-reflecting, the artificial reflections are about 10 − 4 of an incident wave. We have also shown that if a successive refinement is applied, i.e. temporal and spatial steps are refined
at different interfaces, this approach is stable. 相似文献
5.
L. V. Zamana A. B. Ptitsyn G. Chu S. A. Reshetova A. V. Dar’in I. A. Kalugin 《Doklady Earth Sciences》2011,437(1):335-339
On the basis of bottom sediment core dating performed by the technogenic isotope 137Cs, the rate of sedimentation in periodically drying Zun-Torei Lake (water area is up to 300 km2) is estimated at 2.88 mm per year over the last 59 years. This value is in agreement with the data of palinological determinations
(3.44 mm per year). High sedimentation rates are attributed to intensive evaporite sedimentation and probable eolian addition
of terrigenous material. 相似文献
6.
Reshetova S. A. Bezrukova E. V. Tetenkin A. V. Kuzmin M. I. 《Doklady Earth Sciences》2022,501(1):S27-S31
7.
S. A. Reshetova E. V. Bezrukova V. Panizzo A. Henderson A. B. Ptitsyn A. V. Daryin I. A. Kalugin 《Geography and Natural Resources》2013,34(2):172-178
Presented are the latest findings from investigating bottom sediments in Lake Arakhlei, containing continuous records of the vegetation evolution in the Beklemishevskaya depression and its mountain surroundings for the last 13 500 years. 相似文献
8.
Doklady Earth Sciences - A diffuse-interface method for simulating wave fields in saturated elastic porous media is addressed. Wave processes are described by a hyperbolic system of first-order... 相似文献
9.
Localization of fractured areas is of primary interest in the study of oil and gas geology in carbonate environments. Hydrocarbon reservoirs in these environments are embedded within an impenetrable rock matrix but possess a rich system of various microheterogeneities, i.e., cavities, cracks, and fractures. Cavities accumulate oil, but its flow is governed by a system of fractures. A distinctive feature of wave propagation in such media is the excitation of the scattered/diffracted waves by the microheterogeneities. This scattering could be a reliable attribute for characterization of the fine structure of reservoirs, but it has extremely low energy and any standard data processing renders them practically invisible in comparison with images produced by specular reflections. Therefore, any attempts to use these waves for image congestion of microheterogeneities should first have a preliminary separation of the scattering and specular reflections. In this paper, the approach to performing this separation is based on the asymmetric summation. It is implemented by double focusing of Gaussian beams. To do this, the special weights are computed by propagating Gaussian beams from the target area towards the acquisition system separately for sources and receivers. The different mutual positioning of beams in each pair introduces a variety of selective images that are destined to represent some selected singular primitives of the target objects such as fractures, cavities, and edges. In this way, one can construct various wave images of a target reservoir, particularly in scattered/diffracted waves. Additional removal of remnants of specular reflections is done by means of spectral analysis of the scattered/diffracted waves' images to recognize and cancel extended lineaments. Numerical experiments with Sigsbee 2A synthetic seismic data and some typical structures of the Yurubcheno‐Tokhomskoye oil field in East Siberia are presented and discussed. 相似文献
10.
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