A. Yu. Kazansky

Lithogeochemistry of rocks of the Upper Neopleistocene Ust-Oda reference section in the Irkutsk Amphitheater of the Siberian Platform

The results of study of rocks of the Ust-Oda section, one of the key outcrops of Upper Neopleistocene sediments in the Irkutsk Amphitheater of the Siberian Platform, are presented. It is shown that primary sediments were deposited in the Neopleistocene under subarid conditions and relatively high sedimentation rates. Similar contents of trace elements in all rock lithologies suggest that the provenance was unaltered during sedimentation. It is shown that variation in the sediment transport mechanism is one of the signs of changes in the paleoclimatic setting. Climatic cyclicity of the Ust-Oda section formation and succession of sedimentation setting, which were reconstructed on the basis of grain size data, correspond to variations in the petrochemical correlations and geochemical coefficients.

Magnetic Polarity Stratigraphy of the Upper Cenozoic Deposits of Near-Sea Dagestan (Russia) and the Age of the Early Paleolithic Site Rubas-1

We studied magnetic polarity in four Upper Neogene (Akchagylian stage) sections of Near-Sea Dagestan. Paleomagnetic studies have shown that Shor-Dere section is the most complete section of Late Neogene—Late Quaternary in this territory. The section Rubas-1, which contains Paleolithic artifacts, corresponds to the upper part of the Shor-Dere section, while sections Ajinour and Rubas River are likely short fragments, so their correlation with the reference section is ambiguous. A composite magnetic polarity section of Near-Sea Dagestan was constructed on the base of correlation between Shor-Dere, Rubas-1 and, in part, Rubas River sections. Magnetic polarity pattern of the composite paleomagnetic section is well correlated with the polarity zonation of Akchagylian stage for the neighboring regions of the Caspian basin (Azerbaijan and Turkmenistan), the south of the European part of Russia and the Transcaucasia (the Northern Caspian and the Lower Volga region). Such correlation of the magnetic polarity with those from startotype regions of Akchagylian stage made it possible to identify magnetic polarity zones in the composite section with the magnetic polarity chrons of the Neogene and Quaternary Time Scale (2016). We suggest that the upper part of the composite section can be correlated with Matuyama Chron including Olduvai and Reunion subchrons, while the lower part attributes to Gauss Chron with Kaena subchron. The proposed correlation provides the basis for approximate age estimates for the studied strata and supposes the age of the stone industry from Rubas-1 site not later earlier than 2 million years ago.

Basalts of the Zhom-Bolok Lava River as a Possible Sources of Metallic Iron in Sediments of Local Lakes: Thermomagnetic and Microprobe Justification

The results of thermomagnetic and microprobe studies of basalts of the Zhom-Bolok lava river (East Sayan) are given in the article. On the example of the Zhom-Bolok basalt lava river the process of settling of metallic iron particles in a basaltic lava has been demonstrated. Some of examples show the distribution of metallic iron particles during their settling within basaltic lava flows. It has been shown that the main source of metallic iron in lake sediments is the volcanic rocks of the Zhom-Bolok basaltic lava river, detrital material being created through erosion and weathering. Out of numerous studied objects Zhom-Bolok region is a single example of significant enrichment of sediments with metallic iron of terrestrial origin in the immediate vicinity of large eruptions of basaltic lava. Accordingly the halo of scattering of metallic iron particles from the centers of volcanic eruptions and/or the fall of large meteorites and other cosmic bodies to Earth is very limited.

Rock-Magnetism and Granulometry of Late Palaeolithic Sites in the Tunka Rift Valley (Pribaikalie) as a Tool for Reconstruction of Sedimentary Environment

Geological structure, rock-magnetic properties and grain size composition of Late Pleistocene-Holocene sediments containing archaeological horizons with cultural relics have been studied in the Tunka rift valley near Lake Baikal at two archaeological sites: “Tuyana” and “Zaktui”. The closely neighboured sites are in a different geomorphological position: Tuyana is located on the valley slope, while Zaktui sits on the second terrace of Irkut river. The combined analysis of the granulometric and rock-magnetic parameters specifies the genetic deposition types and clarifies the general structure of both sections so that the sedimentation environment in the second half of the Late Pleistocene and Holocene could be reconstructed.

The experience of using the rock magnetic methods for assessing the prospects of magnetic exploration in the territory of archaeological monuments of the Barabinsk forest steppe

The results of studying the magnetic properties of the components of the natural environment of the Barabinsk forest steppe accommodating the archaeological monuments dated to VI century B.C. to II century A.D. are presented. The rock magnetic model is constructed for a two-layer medium composed of modern soil and an underlying blanket substratum deposits (clay loam, sandy loam, sand). It is shown that the magnetism of the humic horizon of the soil depends on the topographic position and soil type, whereas the magnetic characteristics of the underlying substratum deposits are persistent throughout the studied territory. The ratio of the magnetic susceptibilities of the humus horizon to the substratum is K = 3–6 for the automorphic soil, K = 1–2.5 for semihydromorphic soil, and K = 0.8–1.0 for hydromorphic soil. Based on subdividing the studied territory in accordance with the values of K and the calculated amplitudes of the microanomalies of the magnetic field, the areas where application of the magnetic survey is highly promising, moderately efficient, and unpromising are outlined. The particular cases of the absence of magnetic anomalies above the archaeological objects, the false anomalies, and the chaotic patterns of the low-amplitude anomalies—all the situations when the magnetic survey is inefficient—are explained from the standpoint of the model.