Late Permian palaeomagnetic data east and west of the Urals

We studied Upper Permian redbeds from two areas, one between the Urals and the Volga River in the southeastern part of Baltica and the other in north Kazakhstan within the Ural-Mongol belt, which are about 900 km apart; a limited collection of Lower-Middle Triassic volcanics from north Kazakhstan was also studied. A high-temperature component that shows rectilinear decay to the origin was isolated from most samples of all three collections. For the Late Permian of north Kazakhstan, the area-mean direction of this component is D = 224.3°, I =−56.8°, k = 161, Α 95 = 2.7°, N = 18 sites, palaeopole at 53.4°N, 161.3°E; the fold test is positive. The Triassic result ( D = 55.9°, I =+69.1°, k = 208, Α 95 = 4.2°, N = 7 sites, pole at 57.0°N, 134.1°E) is confirmed by a positive reversal test. The corresponding palaeomagnetic poles from north Kazakhstan show good agreement with the APWP for Baltica, thus indicating no substantial motion between the two areas that are separated by the Urals. Our new mean Late Permian direction for SE Baltica ( D = 42.2°, I = 39.2°, k = 94, Α 95 = 3.5°, N = 17 sites; palaeopole at 45.6°N, 170.2°E) is confirmed as near-primary by a positive tilt test and the presence of dual-polarity directions. The corresponding pole also falls on the APWP of Baltica, but is far-sided with respect to the coeval reference poles, as the observed mean inclination is shallower than expected by 13°± 4°. In principle, lower-than-expected inclinations may be attributed to one or more of the following causes: relative tectonic displacements, quadrupole and octupole terms in the geomagnetic field, higher-order harmonics (incl. secular variation) of the same field, random scatter, non-removed overprints, or inclination error during remanence acquisition and/or diagenetic compaction. Our analysis shows that most mechanisms from the above list cannot explain the observed pattern, leaving as the most likely option that it must be accounted for by inclination shallowing. Comparison with selected coeval results from eastern Baltica (all within Russia) shows that all of them are biased in the same way. This implies that they cannot be used for analysis of geomagnetic field characteristics, such as non-dipole contributions, without a more adequate knowledge of the required correction for inclination shallowing.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71899/1/j.1365-246X.2008.03727.x.pd

Quelques caractéristiques de la sédimentation du Crétacé inférieur en Cis-Caucasie à travers les propriétés pétromagnétiques de la couverture sédimentaire

Cet article présente les résultats d\u27une étude pétromagnétique sur les dépôts du Crétacé inférieur du Nord Caucase. Les analyses des propriétés magnétiques des roches ont montré plusieurs poussées de l\u27activité tectonique durant l\u27Hauterivien et le Barrémien. Ces impulsions se sont accompagnées d\u27un transport du matériel terrigène depuis les complexes magnétiques de la ride centrale jusque dans le bassin Cis-Ouralien.This paper present the results from petromagnetic studies of the North Caucasus-Lower Cretaceous deposits. Analyses of the magnetic properties of rocks in base sections have allowed to reveal several impulses of tectonic activation in the Hauterivian and Barremian. The impulses were accompanied by transport of magnetic terrigenous material from the magnetic complexes of the Central Ridge into the Cis-Caucasian Basin.</p

Magnetostratigraphy of the Pliocene deposits in Black Sea, Caspian regions and adjacent areas

Les résultats proviennent d\u27études paléomagnétiques dans les dépôts pliocènes de la Péninsule de Kerch, de Géorgie occidentale, d\u27Azerbaidjan, de Turkménie, du nord de la Cis-Caspienne et de la région du cours inférieur de la Volga. Les informations provenant d\u27autres chercheurs sont utilisées, ainsi que des données de l\u27auteur au sein et antérieures au Programme Péri-Téthys. Les coupes paléomagnétiques composites provenant des régions citées, sont corrélées avec l\u27échelle magnétochronologique (Harland et al. 1982) du Néogène de Méditerranée. Sur la base des données paléomagnétiques, des corrélations chronologiques entre différentes unités locales sont revues. Les principaux stades de développement des faunes d\u27ostracodes et de mollusques de la mer Noire et des régions de la Caspienne sont analysées.The results are summarized of paleomagnetic studies of the Pliocene deposits from Kerch Peninsula, western Georgia, Azerbaijan, Turkmenia, the North Cis-Caspian and Lower Volga regions. Information from a number of researchers was used alongside with the authors data obtained earlier and in the course of research within the framework of the Peri-Tethys Programme. Composite paleomagnetic sections from the areas listed were correlated and related to A. Cox (Harland et al. 1982) magnetochronologic scale and to the paleomagnetic scheme of the Neogene deposits from the Mediterranean region. On the basis of the paleomagnetic data, the views on chronologic relationships among some local stratigraphic units were correcred; main development stages of mollusk and ostracod faunas from the Black Sea and Caspian regions were analyzed.</p

Magnetostratigraphy of the Pliocene deposits in Black Sea, Caspian regions and adjacent areas

Volume: 19Start Page: 471End Page: 49

Some peculiarities concerning the Pliocene evolution of the Black Sea and Caspian basins

Volume: 21Start Page: 477End Page: 48

Some features of the Early Cretaceous sedimentation in the Cis-Caucasia reflected in magnetic properties of the sedimentary cover

Volume: 21Start Page: 365End Page: 38

Depositional conditions in the southern Cis-Urals basin during Late Permian (biostratigraphic, lithofacies and petromagnetic data)

Volume: 19Start Page: 261End Page: 27