L. A. Orlova

Radiocarbon-based chronology of the Paleolithic in Siberia and its relevance to the peopling of the New World.

The territory of Siberia is of crucial importance for the study of early human dispersal and the peopling of the New World. A Siberian Paleolithic Radiocarbon Database has been compiled. The Database allows us to compile a chronological framework for human colonization of Northern Asia. There are 446 (super 14) C dates for 13 Middle and 111 Upper Paleolithic sites older than around 12,000 BP. Seventeen percent of the dates were obtained by the accelerator mass spectrometry (AMS) technique, and the remaining 83% are conventional. From the viewpoint of the spatial distribution of the (super 14) C-dated sites, the majority of these are located at the Yenisey River Basin, Transbaikal, and the Altai Mountains. The general outline of the Upper Paleolithic colonization of Siberia is given here. The earliest traces of modern human occupation are dated to around 43,000-39,000 BP in the southern part of Siberia. It seems that by around 13,000 BP, almost all of northern Asia, including the extreme northeastern Siberia had been colonized by modern humans. We discuss some controversial problems that have provoked heated debates in current Russian archaeology. Notable among these are the surprisingly early AMS dates for the Early Upper Paleolithic, the age of the Dyuktai culture of Yakutia, the problem of human presence in Siberia at the time of the Last Glacial Maximum (20,000-18,000 BP), and the timing of the initial settling of the Chukchi Peninsula and northeastern Siberia.

Carbonates in the sedimentary record of saline Tsagan-Tyrm Lake, west Baikal region: New type of high-resolution paleoclimatic signals

The reasons for catastrophic climate warming have been a matter of heated debates for the past few decades. The issue of the decisive role of anthropogenic factors or natural fluctuations in modern warming can be solved correctly only from paleoclimatic reconstructions, which are mainly based on study of bottom sediments of oceans, seas, and continental lakes. Despite significant intensification of paleoclimatic studies in recent years, one can sense a deficit in reliable data on past climates, especially for intracontinental regions of the large Asian continent. Reference data on this region are represented by the results of deep drilling within the framework of the International Baikal‐Hovsgol Drilling Project in the two largest lakes of the Baikal rift zone (Baikal and Hovsgol). Sedimentary sections of these lakes represent a unique continuous record of climatic and environmental changes in Central Asia for a few million years. In terms of detail, the sections are comparable with records obtained from oceanic muds and Greenland and Atlantic ices. However, intracontinental regions can be characterized by significant local climatic variations related to topography and atmospheric circulation. Therefore, we should examine a significantly greater number of objects. The most promising objects for paleoclimatic studies are the present-day systems of small saline lakes, which can exist only in arid and semiarid conditions [1‐3]. These lakes can provide higher resolution records, because they differ from large basins by lesser conservatism relative to the external impacts. Owing to small dimensions, they rapidly respond to any climatic variations. This paper reports the results of study of the evaporate sediments of one small saline lake in the Ol’khon region (western coast of Lake Baikal) with carbonatetype sedimentation. We attempted to reveal natural assemblages of low-temperature carbonates, crystallochemical and structural features of individual carbonate phases, and their formation sequence in lacustrine sediments depending on the past climatic and environmental variations.

Hydrothermal Activity in the Baikal Rift Zone: Recent Hot Springs and Deposits of Paleothermal Waters

ISSN 1028-334X, Doklady Earth Sciences, 2007, Vol. 412, No. 1, pp. 101–105.

Holocene climate history of the Western Baikal region: Carbonate sedimentary record of Kholbo-Nur Lake

ISSN 1028334X, Doklady Earth Sciences , 2010, Vol. 431, Part 2, pp. 490–496.

Natural-environment dynamics within the Amur basin during the Neoglacial

We examine the natural-environment development dynamics within the Amur basin during the Neoglacial. The study revealed the opposing directedness in climate humidity changes for different parts of the basin. In the maritime and inland parts, a cooling was accompanied by an increase and decrease in humidity, respectively. It is established that a cooling in the maritime part of the basin led to a shift of the boundaries of vegetation zones, an enhancement in waterlogging of bog systems, and to a change of biogeocenoses. In the inland part of the basin, an enhancement in aridization was conducive to a retrogression of the lakes’ level, and to an intensification of aeolian processes.

Radiocarbon dating of buried Holocene soils in Siberia.

We have constructed a detailed chronological description of soil formation and its environments with data obtained on radiocarbon ages, palynology, and pedology of the Holocene buried soils in the forest steppe of western and central Siberia. We studied a number of Holocene sections, which were located in different geomorphic situations. Radiocarbon dating of materials from several soil horizons, including soil organic matter (SOM), wood, peat, charcoal, and carbonates, revealed three climatic periods and five stages of soil formation in the second part of the Holocene. (super 14) C ages of approximately 6355 BP, 6020 BP, and 5930 BP showed that the longest and most active stage is associated with the Holocene Climatic Optimum, when dark-grey soils were formed in the forest environment. The conditions of birch forest steppe favored formation of chernozem and associated meadow-chernozem and meadow soils. Subboreal time includes two stages of soil formation corresponding to lake regressions, which were less intense than those of the Holocene Optimum. The soils of that time are chernozem, grassland-chernozem, and saline types, interbedded with thin peat layers (super 14) C dated to around 4555 BP, 4240 BP and 3480 BP, and 3170 BP. Subatlantic time includes two poorly developed hydromorphic paleosols formed within inshore parts of lakes and chernozem-type automorphic paleosol. The older horizon was formed during approximately 2500-1770 BP, and the younger one during approximately 1640-400 BP. The buried soils of the Subatlantic time period also attest to short episodes of lake regression. The climate changes show an evident trend: in the second part of the Atlantic time period it was warmer and drier than at present, and in the Subboreal and Subatlantic time periods the climate was cool and humid.

Paleoseismicity in cis-Baikal rift basins: Evidence and age constraints

Recent years have witnessed considerable advances in the study of deformation structures caused by soil liquefaction during seismic shocks [1‐5]. These structures are clear paleoearthquake indicators [2] that can be used for determining various parameters of past events [3‐5]. This paper deals with identification, structural and geological study, and dating of the sections that contain seismites, clastic dykes, dislocation cracks, and paleosols buried as a result of rapid tectonic downthrows in the Tunka and Barguzin valleys of the cis-Baikal Area (Fig. 1). The sections with structures indicative of past seismic events were identified along the fault zones that had been previously mapped [6, 7] and ranked as hazardous based on several features [8]. In six stations the deformed sediments were carbon dated (table). The residual carbon activity was measured at the Institute of Geology and Mineralogy (Novosibirsk). Based on a half-life of 5570 years, the age was calculated started at 1950. Below is a short description of the sections and a discussion of the results. Section T0201 in descending order consists of (1) a recent soil and vegetation horizon, 0‐0.08 m; (2) sand loam, 0.08‐0.32 m; (3) laterally persistent paleosol with a disturbed lower part, 0.32‐0.5 m; (4) mediumgrained, limonitized, and strongly deformed sand, with fragments of clay loam and paleosol that previously formed a continuous layer, 0.5‐1.15 m; (5) limonitized clay loam with signatures of seismic shocks in the form of waves, 1.15‐1.57 m; and (6) medium-grained sand with seismites in the form of mushroom- or dropshaped injections into the overlying layer, 1.57‐2.0 m. The lack of inclinations and swellings on the daylight surface of the section suggested that gravity sliding or cryogenic processes were not involved in the origin of the deformations. There are normal faults in the section with dip and dip direction 70/290 that together with the patterns in deformation (Fig. 2a) prove the seismic origin of the observed structures. The dates obtained (table) suggest that the soil fragments in layer 4 represent a once continuous paleosol distinct from layer 3.

New Data on Environments of Cisbaikalia in the Late Holocene

New data on changes in late Holocene environments of Cisbaikalia have been obtained based on integrated studies of the mode of occurrence, genetic types, stratigraphy, and data on absolute geochronology and morphology, as well as palynological, chemical, and grain size compositions of paragenetically related loose sediments of key sections in the central part of the western coast of Lake Baikal. The sections are located in piedmont‐saddle (the Bezymyannyi section) and floodplain‐valley (the Kuchelga section) geomorphological conditions (Fig. 1). Environments of the Subboreal and Subatlantic intervals of the Holocene were reconstructed based on the analysis of loose sediments of the Bezymyannyi section. The section is located in the water-logged, birch‐willow, underbrush (dogrose and currant), and moss‐sedge forest in the subaqueous (high floodplain) area between the Kuchelga River channel and the Bezymyannyi Creek at the foothill of the Primorskii Range. The forest is surrounded by petrophyte thin larch forest with stepped herbs and undergrowth (spiraea and cotoneaster), birch, and aspen. The section is located at the foothill‐saddle surface (slope 1°–3° ) characterized by the minimum influence of gravitational agents of morphogenesis. The basic results of the study of loose sediments in this section are presented below. The total thickness of the section is 95 cm. Mineralized peat deposits occur down to the depth of 42 cm. A fragment of a buried cedar trunk was found at a depth of 22‐32 cm. Five radiocarbon ages have been obtained for this part of the section (table). Interval 78‐95 cm. Sediments of this interval accumulated under hydrogeodynamic conditions with a stable regime of atmospheric precipitation, which afforded sand deposition and brought debris of medium roundness during snow melting, indicating a constancy of water flow. Such conditions seem to be typical for the end of the Atlantic interval of the Holocene. We failed to reconstruct paleovegetation due to the lack of pollen in this bed, probably because of the large size of sand grains in this bed (as compared to spore-and-pollen) and their consequent removal.

14C chronology of late Pleistocene-Holocene events in the Nizhnee Priamurie (Southeast Russia)

The Russian Far East is characterized by widespread peat bogs with a sufficiently thick peat accumulation. A series of radiocarbon dates from the studied peat bogs (in Lower Amur) were obtained. Analysis of these dates shows that the total peat formation in this territory began in the Late Pleistocene-Holocene (11,830+ or -820, TIG-157; 9975+ or -120, SOAN-4025). The rates of peat accumulation and the humidity index were counted. In addition, the botanical composition and degree of peat decomposition were defined. These data allow to study in more detail climate fluctuation and the (super 14) C chronology of Holocene events in the region studied.