Types of variations in the geomagnetic field spectrum

The purpose of archaeomagnetic research is to investigate the structure of the geomagnetic field and its evolution. This paper is a study of this type. In our preceding studies, we divided the geomagnetic field into dipole and nondipole components. It was then shown that the dipole component consists of the predominant 1200-yr variation and the remainder δ. The δ variation is the subject of this paper. Detailed study and comparison of the characteristic features of two 1200-yr variations (the dipole and δ variations) in both the declination and inclination indicates that, according to most of their features, they can be assigned to different types of waves, namely, traveling waves (the dipole variation) and standing waves (the δ variation). Successive averaging in time and space yielded averaged data on δI and δD not only for various parts of the world (Europe, Asia, and America) but also for the western and eastern hemispheres.     

Application of a Continuous Wavelet Transform to Study Planetary Waves

Izvestiya, Atmospheric and Oceanic Physics - In this paper, we show a method for using the continuous Morlet wavelet transform in studying the variability of atmospheric migrating and nonmigrating...     

Density Structure of the Lithosphere of the Sikhote-Alin Orogenic Belt

Doklady Earth Sciences - For the first time, a detailed density 3D model of the lithosphere of the Sikhote-Alin orogenic belt to a depth of 130 km has been created. Two extended submeridional...     

The fine structure of the geomagnetic field

It was shown in our previous works that the dipole part of the geomagnetic field direction is mainly represented by the 1200-yr variation. According to some indications, the residual of the dipole part of the field, the so-called δ variation, may be classified as standing waves. Average values of δ are calculated for each hemisphere. In this work, the difference values equal to the δ variations for each territory minus δ averages over hemispheres (western or eastern) are calculated. The resulting values, fine structure (FS) variations, characterize the FS of the geomagnetic field. The study of the activity of the FS variations and specific features of their N-S and E-W behavior and the comparative analysis of dynamic characteristics (activity and rate) give grounds to classify the FS variations (as well as the δ variations) as standing waves of the nondipole field.     

The junction of the eastern Central Asian Fold Belt and the Siberian Platform: deep structure and Mesozoic tectonics and geodynamics

The tectonic structure of the junction of the eastern Central Asian Fold Belt and the Siberian Platform, along with the deep structure of the Earth's crust and lithosphere in this region, has been described on the basis of new geological and geophysical data (seismic, geoelectric, and space-structural studies as well as new-generation geological maps), combined with new interpretation techniques (processing of the previous data by special software). The data suggest the existence of oblique collision during the convergence of the tectonic plates and, correspondingly, tectonic units composing these plates, when the Mongol–Okhotsk paleobasin closed. Such a scenario within the Aldan–Stanovoi Shield is evidenced by areas of syn- and postcollisional magmatism, with their deep-level and geochemical characteristics, and by the presence of a Late Mesozoic fold–thrust zone. Deep “traces” of these tectonomagmatic events, detected in the course of geological and geophysical modeling, are manifested in inclined deep boundaries between the crustal and lithospheric blocks. On the Earth's surface, they correspond to large fault systems: the Dzheltulak, North and South Tukuringra, Gulyui, and Stanovoi. It has been found that the influence of collision decreases northward with distance from the junction of the eastern Central Asian Fold Belt and the Siberian Platform (Dzheltulak and North Tukuringra transcrustal faults).     

Eastern segment of the Kiselevka-Manoma terrane (Northern Sikhote Alin): Paleomagnetism and geodynamic implications

The comprehensive geological-geophysical study of the lower Cretaceous volcanosedimentary rocks of the Kiselevka block of the Kiselevka-Manoma lithotectonic terrane made it possible to reach the following conclusions: (1) The composition of the volcanogenic rocks and the lithology of the sediments of the Kiselevka block indicate their formation in a within-plate oceanic setting; the petro- and geochemical characteristics of the studied volcanic rocks are similar to those of the Hawaiian hot spot. (2) The distinguished characteristic component of the natural remanent magnetization of the volcanosedimentary rock complex of the Kiselevka block yields a positive fold test and age similar to that of the rocks. According to the orientation of this characteristic component, the paleolatitudes of the rock formation (18° ± 5° N) and the coordinates of the paleomagnetic pole (Plat = 18.6°, Plong = 222.4°, dp = 5.2, dm = 9.1°) of the Kiselevka Block were determined. (3) The kinematic reconstructions based on the obtained and published data indicate that, (1) in the Valanginian-Albian, the Kiselevka Block migrated northwestward with the Izanaga Plate at a velocity of 15–20 cm/yr, passing over 5 thou. km up to the Eurasian margin (the Korean Peninsula); (2) in the Albian-Campanian, the block, as a fragment of the Kiselevka-Manoma accretionary wedge, moved along the Eurasian transform margin with a velocity of 4–5 cm/yr to its present-day position, where it was integrated into the continental plate.     

Paleomagnetism of granites from the Angara-Kan basement inlier,Siberian craton

We report a new paleomagnetic determination of Paleoproterozoic rocks from the Siberian craton which showed a positive baked contact test and a stable age of the high-temperature NRM component. The mean paleomagnetic pole of Siberia for ～1730 Ma located at 42.9° S, 109.6° E (α95 = 5.3°) is compatible with the pole positions obtained recently for the middle and late Early Proterozoic.     

Paleomagnetism of the Ulkan trough (Southeastern Siberian Craton)

The first results of the paleomagnetic study of one of the key Paleoproterozoic objects of the Aldan-Stanovoy Shield (the Ulkan trough) in the Bilyakchan-Ulkan volcanoplutonic belt are presented. The volcanosedimentary rocks of the Elgetei Formation and the granites of the Ulkan Complex were studied. According to these data and their comparison with the apparent Paleoproterozoic polar wandering path in the Angara-Anabar province, the Ulkan trough was (1) located during the timing of the studied rocks at 18°–26° S and (2) subjected to rotation (relative to the Angara-Anabar block) at 70° ± 8° in the time interval of 1732–1720 Ma ago. Based on the combined interpretation of the paleomagnetic, geochronological, and geochemical data published previously, a paleogeodynamic model is proposed. According to this model, the Aldan-Stanovoy and Angara-Anabar provinces of the Siberian Craton became a single rigid block about 1720 Ma ago.