Possibilities and specific features of pulsed inductive electromagnetic sounding of shallow sections under complex geological conditions

A new high-resolution technology of pulsed induction electrical survey is developed for sounding with small (2–30 m) loops in the depth interval from 0.5 to a few hundred meters (in its possibilities, this technology is unprecedented). The specific feature of the proposed technology is that it is applicable not only to well conducting and contrasting objects but also to sounding of low conductivity and low contrast geological objects (including those overlain by high and low resistivity screens) and to identification of thin and low contrast beds. The minimum initial time of recording the useful signal is 350 ns at a current of 3 A. The accuracy of the location of an interface between layers attains 2–5%. The interpretation results are close to electrical logging data. Testing methodological studies were carried out in the Malo-Batuobinskaya diamondiferous province of the Yakutian permafrost zone and in the inspection of high embankments and two landslides in a railroad zone. The new technology can be used in the presence of intense electromagnetic interferences (in particular, along electrified railroad tracks).     

The first magnetostratigraphic data on the stratotype of the Lopata Formation,Northeastern Yenisei Ridge: Problems of its age and paleogeography of the Siberian Platform at the Proterozoic–Phanerozoic boundary

New paleomagnetic and magnetostratigraphic data are presented for the stratotype of the Upper Riphean Lopata Formation (Teya River, Yenisei Ridge). The paleomagnetic pole calculated is significantly distinct from the Phanerozoic and Riphean poles of the Siberian Platform and is similar to the Late Vendian–Early Cambrian poles of the Madagascar Group. The stratigraphic range studied is characterized by an anomalously high frequency of geomagnetic inversions (15 zones of magnetic polarity), which is comparable with the inversion frequency of the Late Vendian sections of Baltica. These data, along with previous paleontological findings, indicate an age of the Lopata Formation of 555–540 Ma.     

Impact of anthropogenic and natural factors on the air quality above the northern Caspian Sea and the ecological risk level for the human population in the coastal zone

The paper reports monitoring results (obtained in 2000–2001) of the seasonal variations in the quality of lower atmospheric air in the coastal zone of the northern Caspian Sea due to the occurrence of aerosols with submicrometer-sized particles and soot in the lower atmosphere. The contributions of natural and anthropogenic factors to the ecological risk for the local human population are evaluated, along with the contribution of the premature mortality of the human population in the coastal zone in 2005 to its overall average death rate for the Russian Federation (approximately 24%). The authors’ estimates are consistent with those made by the World Health Organization at the United Nations (WHO) for the Russian Federation as a whole (approximately 21%). The information presented in this publication is important for evidence-based recommendations on preventive environment-protective measures to be taken with regard for the development of oil and gas fields on- and offshore the northern Caspian Sea.     

Function of distribution of clouds’ optical thickness over the West Siberian Plain

Results of measurements of optical thickness of clouds over the West Siberian Plain taken with the help of the MERIS spectrometer onboard the European satellite ENVISAT are analyzed. The observational data for two summer periods of 2008–2009 are considered. It is found that the distribution function of the clouds’ optical thickness averaged over the territory is best presented as the sum of three logonormal distributions. The contribution from each of them to the total envelope, values of optical thickness logarithms for mode centers, and values of variances are given. It is shown that the distribution parameters are almost unchanged with conditional division of the plain’s territory into four zones. The total number of the studied cases exceeds 10⁶.     

The North Taymyr ice-marginal zone, Arctic Siberia—a preliminary overview and dating

The North Taymyr ice-marginal zone (NTZ) is a complex of glacial, glaciofluvial and glaciolacustrine deposits, laid down on the northwestern Taymyr Peninsula in northernmost Siberia, along the front of ice sheets primarily originating on the Kara Sea shelf. It was originally recognised from satellite radar images by Russian scientists; however, before the present study, it had not been investigated in any detail. The ice sheets have mainly inundated Taymyr from the northwest, and the NTZ can be followed for 700–750 km between 75°N and 77°N, mostly 80–100 km inland from the present Kara Sea coast.The ice-marginal zone is best developed in its central parts, ca. 100 km on each side of the Lower Taymyr River, and has there been studied by us in four areas. In two of these, the ice sheet ended on land, whereas in the two others, it mainly terminated into ice-dammed lakes. The base of the NTZ is a series of up to 100-m-high and 2-km-wide ridges, usually consisting of redeposited marine silts. These ridges are still to a large extent ice-cored; however, the present active layer rarely penetrates to the ice surface. Upon these main ridges, smaller ridges of till and glaciofluvial material are superimposed. Related to these are deltas corresponding to two generations of ice-dammed lakes, with shore levels at 120–140 m and ca. 80 m a.s.l. These glacial lakes drained southwards, opposite to the present-day pattern, via the Taymyr River valley into the Taymyr Lake basin and, from there, most probably westwards to the southern Kara Sea shelf.The basal parts of the NTZ have not been dated; however, OSL dates of glaciolacustrine deltas indicate an Early–Middle Weichselian age for at least the superimposed ridges. The youngest parts of the NTZ are derived from a thin ice sheet (less than 300 m thick near the present coast) inundating the lowlands adjacent to the lower reaches of the Taymyr River. The glacial ice from this youngest advance is buried under only ca. 0.5 m of melt-out till and is exposed by hundreds of shallow slides. This final glaciation is predated by glacially redeposited marine shells aged ca. 20,000 BP (¹⁴C) and postdated by terrestrial plant material from ca. 11,775 and 9500 BP (¹⁴C)–giving it a last global glacial maximum (LGM; Late Weichselian) age.     

Effect of the zonal E × B plasma drift on the electron number density in the low-latitude ionospheric F region at high solar activity near the December solstice

The variations in the electron number density of the ionospheric F2 layer maximum (NmF2) under the action of the zonal plasma drift in the geomagnetic west-geomagnetic east direction perpendicularly to the electric (E) and geomagnetic (B) fields during a geomagnetically quiet period on December 7, 1989, at high solar activity have been studied based on a three-dimensional nonstationary theoretical model of electron number densities and temperatures in the ionospheric F region. Calculated and measured NmF2 values for 12 low-latitude ionospheric sounding stations have been compared. When the zonal E × B plasma drift is ignored, the NmF2 values become smaller by up to a factor of 3 under nighttime conditions in the low-latitude ionosphere. The average effect of the zonal E × B plasma drift on NmF2 in the low-latitude ionosphere is larger during winter nights than under summer nighttime conditions.