Formation conditions and regularities of the distribution of large and superlarge bauxite deposits

A brief characteristic of three genetic groups of large and superlarge (lateritic, sedimentary, and karstic) bauxite deposits is presented. Their structure, composition, formation conditions, and localization patterns in the Earth’s Phanerozoic history are unraveled. Climatic, tectonic, geomorphological, hydrogeological, and other major factors favorable for bauxite formation are scrutinized. It is shown that only the combination of these factors produces large deposits that can make up productive bauxite ore districts and provinces.     

Phanerozic bauxite epochs

The Early Cambrian, Middle and Late Devonian, Middle and Late Carboniferous, Permian, Late Triassic-Early Jurassic, Late Cretaceous, Paleocene-Eocene, and Miocene epochs of bauxite formation have been the most productive. They lasted for no less than 10 Ma. The scope of bauxite deposition of various epochs is shown in the diagram, and the present-day localization of Cenozoic, Mesozoic, and Paleozoic bauxites is depicted in separate maps. The Cenozoic bauxite deposits are located in tropical and subtropical zones of the Southern and Northern hemispheres. The Mesozoic deposits occur in the Northern Hemisphere as far north as 50°N, and the Paleozoic deposits, as far north as 70°N. Palinspastic reconstructions show that during all the aforementioned epochs, bauxites were deposited at paleotropical latitudes. The current localization of the Paleozoic and Mesozoic bauxites at high latitudes up to the Polar Circle is caused by continental drift to the north in the Phanerozoic.     

Bauxite provinces of the world

Phanerozoic bauxite provinces are contoured and characterized. The relations to large tectonic units—ancient and young platforms, island arcs and foldbelts, active continental margins, etc.—are chosen as the major criterion for the recognition of bauxite provinces; 19 provinces of different age and conditions of bauxite deposition are described. Single- and multistage as well as single- and multilevel provinces are distinguished depending on the type of tectonic and geomorphic structure. The most productive bauxite provinces are located in the present-day tropical zone within ancient Gondwanan platforms. Three-level provinces with Cretaceous bauxite at the highest and oldest (post-Gondwanan) surface and Cenozoic deposits at lower and younger planation surfaces are predominant. The most complex, two- and three-stage and multilevel provinces are related to ancient fold regions. The single-level provinces are localized in young island arcs and oceanic islands. The prevalent genetic types of bauxite deposits—lateritic, sedimentary, and karst—are shown in the map of bauxite provinces.     

Reversal of Heliospheric Magnetic Field Polarity: Theoretical Model

A simple analytical model of the reversal of the heliospheric magnetic field is suggested. The shape of the heliospheric current sheet is found for each instant of time using a kinematic approximation. Calculation results are illustratively presented in graphic and animated forms, showing a 3-D dynamic picture of the reversal of the heliospheric magnetic field throughout a 22-year solar cycle.     

Methods and statistics of TV observations of telescopic meteors

A review of TV and telescopic methods of meteor observations and of the problems of meteor astronomy addressed using these methods is presented. A meteor patrol developed at the Astronomical Observatory of Odessa National University and based on a Schmidt telescope and a TV detector is described. The meteor patrol allows meteor events to be recorded with a time resolution of 0.04 s. The investigated characteristics of the patrol are reported, and some aspects of the methods of observations and reduction employed are considered. The results of observations made during the period 2003–2004 are reported. A total of 368 meteors were recorded on 1093 individual frames during a total patrol time of 679 hours within a 36′ × 48′ field of view. The statistical data for meteor observations are reported, and classification of meteor images is presented. The specific features of some recorded meteor events are analyzed.     

Structure and Formation Conditions of the Bazhenovo Horizon in the Pal’yanovo Area,West Siberia

Comprehensive studies of cores from 7 boreholes drilled in the Pal’yanovo area provided insight into the Bazhenovo Horizon in southwestern Siberia represented by the lower subformation of the Tutleim Formation. The work presents a typification of organic-rich biogenic-terrigenous rocks. The Bazhenovo Horizon is divided into 11 lithotypes grouped into 5 large members. Members I?IV correspond to the lower subformation of the Tutleim Formation; member V, to the upper subformation. The identified members are traced explicitly over the Pal’yanovo area, making it possible to examine the whole vertical succession of the Tutleim Formation and reconstruct its evolution based on the proposed sedimentation model.     

PROBLEMS OF THE COMPLEX AUTOMATED MAPPING OF THE MOSCOW REGION

The paper describes a program for the complex (comprehensive) automated mapping of Moscow Oblast, performed jointly by various departments within the Moscow University Geography Faculty. The program was instituted during the Eleventh Five-Year Plan (1981-1985) and includes among its objectives: (1) support for local economic management and planning; (2) promotion of basic research in automated cartographic and geographic information systems; and (3) the improvement of methods of complex mapping. A number of maps compiled to date are described, and sample maps produced by the Moscow University Automated Mapping System are presented. Translated from: Vestnik Moskovskogo Universiteta, geografiya, 1988, No. 1, pp. 54-59 by Jay K. Mitchell; PlanEcon, Inc.; Washington, DC 20005.     

Estimating Travel Times of Coronal Mass Ejections to 1 AU Using Multi-spacecraft Coronagraph Data

We study the relationship between the speeds of coronal mass ejections (CMEs) obtained close to the Sun and in the interplanetary medium during the low solar-activity period from 2008 to 2010. We use a multi-spacecraft forward-modeling technique to fit a flux-rope-like model to white-light coronagraph images from the STEREO and SOHO spacecraft to estimate the geometrical configuration, propagation in three-dimensions (3D), and the radial speeds of the observed CMEs. The 3D speeds obtained in this way are used in existing CME travel-time prediction models. The results are compared to the actual CME transit times from the Sun to STEREO, ACE, and Wind spacecraft as well as to the transit times calculated using projected CME speeds. CME 3D speeds give slightly better predictions than projected CME speeds, but a large scatter is observed between the predicted and observed travel times, even when 3D speeds are used. We estimate the possible sources of errors and find a weak tendency for large interplanetary CMEs (ICMEs) with high magnetic fields to arrive faster than predicted and small, low-magnetic-field ICMEs to arrive later than predicted. The observed CME transit times from the Sun to 1?AU show a particularly good correlation with the upstream solar-wind speed. Similar trends have not been observed in previous studies using data sets near solar maximum. We suggest that near solar minimum a relatively narrow range of CME initial speeds, sizes, and magnetic-field magnitudes led to a situation where aerodynamic drag between CMEs and ambient solar wind was the primary cause of variations in CME arrival times from the Sun to 1?AU.