Geochemistry of Diagenesis of Organogenic Sediments: An Example of Small Lakes in Southern West Siberia and Western Baikal Area

Organogenic sediments (sapropels) in lakes are characterized by a reduced type of diagenesis, during which organic compounds are decomposed, the chemical composition of the pore waters is modified, and authigenic minerals (first of all, pyrite) are formed. Pyrolysis data indicate that organic matter undergoes radical transformatons already in the uppermost sapropel layers, and the composition of this organic matter is principally different from the composition of the organic matter of the its producers. The sapropels contain kerogen, whose macromolecular structure starts to develop during the very early stages of diagenesis, in the horizon of unconsolidated sediment (0–5 cm). The main role in the diagenetic transformations of organic matter in sediments is played by various physiological groups of microorganisms, first of all, heterotrophic, which amonifying, and sulfate-reducing bacteria. SO₄^2? and Fe²⁺ concentrations in the pore waters of the sediments are determined to decrease (because of bacterial sulfate reduction), while concentrations of reduced Fe and S species (pyrite) in the solid phase of the sediment, conversely, increase. Comparative analysis shows that, unlike sapropels in lakes in the Baikal area, sapropels in southern West Siberia are affected by more active sulfate reduction, which can depend on both the composition of the organic matter and the SO₄^2? concentration in the pore waters.     

The Phosphates of Pleistocene–Holocene Sediments of the Eastern Gallery of Denisova Cave

Authigenic phosphate mineralization was first studied on the territory of Russia on the basis of the Holocene and Pleistocene deposits of Denisova Cave. The formation of phosphates in the eastern gallery is related to biodegradation of the horizons of guano of insectivorous bats, which inhabited the cave in the absence man. The results confirmed the archaeological record of the Holocene and the upper part of Pleistocene sequences of the eastern gallery.     

First results of GPS measurements on the Ulaanbaatar geodynamic testing area

First results of the analysis of GPS measurement data obtained from 18 sites of two local networks in the vicinity of Ulaanbaatar (Mongolia) for the period 2010–2015 have been presented. Horizontal velocity vectors are consistent with each other in the ITRF2014 system and with the velocities of the IGS permanent station ULAB. The sites move in the E–SE direction at a rate of 25–30 mm/yr, with the displacement azimuth averaging 105°. With respect to Eurasia, the vectors for most of the sites are slighly turned to the south, but they are still of SE orientation with the azimuth range of 130°–150° and magnitude values of 2–4 mm/yr. Relative horizontal velocities tend to decrease towards southeast that determines a zonal distribution of different type of relative strain patterns. The western part of the Ulaanbaatar network is characterized by the W–E oriented extension with the elongation rate ε₁ = 12–16 × 10^–8 yr^–1. The shortening NW–SE trending strain with calculated value ε₂ = 22.4 × 10^–8 yr^–1 characterizes the network’s eastern part. The highest values of the maximum shear strains (ε_max = 10–14 × 10^–8 yr^–1) form an extended area in the center of the testing ground, which is elongated in the northeastern direction, conformably with the strike of the major geologic structures. The strain distribution pattern of the Emeelt network located within the eponymous seismogenic structures is characterized by the crustal elongation (5 × 10^–6 yr^–1) trending SE–NW and less pronounced shortening in the SW–SE directions.The axial part of the fault crossing the network in the NW direction exhibits maximum deformations.     

Solar cosmic rays: 70 years of ground-based observations

The main data have been summarized, and the results, achieved using data from the worldwide network during the entire period of ground-based observations of solar cosmic rays (SCRs) from February 28, 1942, when they were discovered, have been generalized. The methods and equipment for registering SCRs have been described. The physical, methodical, and applied aspects, related to the SCR generation, as well as the SCR interaction with the solar atmosphere, transport in the IMF, motion in the Earth’s magnetosphere, and the affect on the Earth’s atmosphere, have been discussed. It has been indicated that the fundamental results were achieved in this field of space physics during 70 years of studies. Special attention has been paid to up-to-date models and concepts of ground-level enhancement (GLE). The most promising tendencies in the development and application of this effective method of solar-terrestrial physics have been outlined.     

GPS rotation and strain rates in the Baikal–Mongolia region

Current deformation in Pribaikalia, Western and Central Mongolia, and Tuva has been studied from measured horizontal GPS velocities and respective computed strain and rotation rates using 1994–2007 data of the Baikal–Mongolian GPS triangulation network.The GPS velocity field shows two main trends: an NE trend within Jonggaria, the Mongolian Altay, and the Great Lakes Valley and an SE trend in the Hangayn and eastern Gobi Altay mountains, and in the Transbaikalian block of the Amur plate. The velocity magnitudes and vectors are consistent with an SE motion of the Amur plate at a rate of ～2 mm/year.The derived strain pattern includes domains of crustal contraction and extension recognized from the magnitudes of relative strains. Shortening predominates in the Gobi and Mongolian Altay and in the Khamar-Daban Range, where it is at ?₂ = (19.2 ± 6.0)×10^?9 yr^?1 being directed northeastward. Extension domains exist in the Baikal rift and in the Busiyngol–West Hangayn area, where the crust is stretching along NW axes at ?₁ = (22.2 ± 3.1) × 10^–9 yr^–1. The eastern Hangayn dome and the Gobi peneplain on its eastern border show low and unstable strain rates. In central and northern Mongolia (Orhon–Selenge basin), shortening and extension are at similar rates: ?₂ = (15.4 ± 5.4)×10^?9 yr^?1 and ?₁ = (18.1 ± 3.1)×10^?9 yr^?1. The strain pattern changes notably in the area of the Mogod earthquake of 1967.Most of rotation throughout Central Asia is clockwise at a low rate of about Ω = 6×10^?9 deg·yr^?1. High rates of clockwise rotation are observed in the Hangayn domain (18.1 ± 5.2)×10^?9 deg·yr^?1, in the Gobi Altay (10.4 ± 7.5)×10^?9 deg·yr^?1, and in the Orhon–Selenge domain (11.9 ± 5.2)×10^?9 deg·yr^?1. Counterclockwise rotation is restricted to several domains. One is in western Tuva and northwestern Great Lakes Valley of Mongolia (Ω = 3.7×10^?9 deg·yr^?1). Two more counterclockwise rotation regions occur on both flanks of the Baikal rift: along the craton edge and in basins of Transbaikalia on the rift eastern border, where rotation rates are as high as (13.0 ± 3.9)×10^?9 deg·yr^?1, while rotation within the Baikal basin does not exceed the measurement error. Another such domain extends from the eastern Hövsgöl area to the Hangayn northern foothills, with the counterclockwise rotation at a highest rate of (16.3 ± 2.8)×10^?9 deg·yr^?1.