New Geophysical Data About the Pacific Margin (West Antarctica) Magnetic Anomaly Sources and Origin

During the seasonal work in the Ukrainian Antarctic expeditions (1997—2012), a significant amount of geological and geophysical studies were carried out. The main objective of the study is to obtain new data on the distribution of deep heterogeneities in the structures of the region. It’s allowed to construct the geophysical models and to discuss the existing ideas about the stages of formation and evolution tectonic structures of the West Antarctica near the Antarctic Peninsula (AP). New geophysical models of the Earth's crust were used to study the possible nature of the Pacific Coast magnetic anomaly (PMA) near the AP.Під час проведення сезонних робіт в українських антарктичних експедиціях (1997—2012 рр.) був виконаний значний обсяг геолого-геофізичних досліджень з метою отримання нових даних про розподіл глибинних неоднорідностей в структурах регіону, що дозволило побудувати комплексні геофізичні моделі та доповнити наявні уявлення про етапи формування та еволюції тектонічних структур Західної Антарктики поблизу Антарктичного півострова (AП)

CP violating neutrino oscillation and uncertainties in Earth matter density

We propose a statistical formulation to estimate possible errors in long baseline neutrino oscillation experiments caused by uncertainties in the Earth matter density. A quantitative investigation of the effect is made on the CP asymmetry in future neutrino factory experiments.Comment: Latex, 10 pages, 5 figure

Crustal and upper mantle structure beneath the Donets Basin and Donbas Foldbelt from 3-D gravity modelling.

The Dniepr-Donets Basin (DDB) is a linear, NW-SE trending, late Palaeozoic and younger sedimentary basin on the East European Platform separating the Ukrainian Shield from the Voronezh Massif. Its northwestern (Dniepr) segment has the characteristics of a typical rift basin. To the southeast, through a transition zone of approximately 200 km length, the DDB is progressively uplifted and compressionally deformed into the correlatable Donbas Foldbelt (DF). Along the axis of the Dniepr segment a series of gravity highs has been previously explained by high-density crystalline crust beneath the axis of the basin caused by intrusion of mafic and ultramafic rocks. In this paper, the results of a 3-D gravity analysis, using a gravity backstripping technique, is described that investigates the crustal and upper mantle structure in the region of the DDB-DF transition zone and DF. A residual gravity field I, obtained by subtracting the gravity influence of the sedimentary succession of the DDB from the observed field, reveals a distinct positive anomaly along the axis of the rift basin increasing in amplitude to the southeast in concert with increasing sedimentary thickness. A residual gravity field II, derived by removing the gravity effects of a modelled homogeneous crystalline crust from residual field I, reaches 200 and 100 mGal amplitude in the DF for two respective Moho models based on different interpretations of the published crust and upper mantle seismic velocity models. The first of these (model A) assumes crustal thickening beneath the transition zone and DF (to a Moho depth up to 50 km) whereas the second (model B) assumes a Moho shallowing (to depths in the range 35-37 km) along the whole basin axis. For each residual anomaly II, the best-fitting 3-D distribution of average density in the crystalline crust has been computed. Both models indicate the existence of a high-density body in the crystalline crust along the DDB axis, increasing in density from the Dniepr segment to the DF, with higher average crustal density required in the case of Moho model A (3.17 x 1

Structure of the lithosphere below the southern margin of the East European Craton (Ukraine and Russia) from gravity and seismic data.

The present study was undertaken with the objective of deriving constraints from available geological and geophysical data for understanding the tectonic setting and processes controlling the evolution of the southern margin of the East European Craton (EEC). The study area includes the inverted southernmost part of the intracratonic Dnieper-Donets Basin (DDB)-Donbas Foldbelt (DF), its southeastern prolongation along the margin of the EEC-the sedimentary succession of the Karpinsky Swell (KS), the southwestern part of the Peri-Caspian Basin (PCB), and the Scythian Plate (SP). These structures are adjacent to a zone, along which the crust was reworked and/or accreted to the EEC since the late Palaeozoic. In the Bouguer gravity field, the southern margin of the EEC is marked by an arc of gravity highs, correlating with uplifted Palaeozoic rocks covered by thin Mesozoic and younger sediments. A three-dimensional (3D) gravity analysis has been carried out to investigate further the crustal structure of this area. The sedimentary succession has been modelled as two heterogeneous layers-Mesozoic-Cenozoic and Palaeozoic-in the analysis. The base of the sedimentary succession (top of the crystalline Precambrian basement) lies at a depth up to 22 km in the PCB and DF-KS areas. The residual gravity field, obtained by subtracting the gravitational effect of the sedimentary succession from the observed gravity field, reveals a distinct elongate zone of positive anomalies along the axis of the DF-KS with amplitudes of 100-140 mGal and an anomaly of 180 mGal in the PCB. These anomalies are interpreted to reflect a heterogeneous lithosphere structure below the supracrustal, sedimentary layers: i.e., Moho topography and/or the existence of high-density material in the crystalline crust and uppermost mantle. Previously published data support the existence of a high-density body in the crystalline crust along the DDB axis, including the DF, caused by an intrusion of mafic and ultramafic rocks during Late Palaeozoic rifting. A reinterpretation of existing Deep Seismic Sounding (DSS) data on a profile crossing the central KS suggests that the nature of a high-velocity/density layer in the lower crust (crust-mantle transition zone) is not the same as that of below the DF. Rather than being a prolongation of the DDB-DF intracratonic rift zone, the present analysis suggests that the KS comprises, at least in part, an accretionary zone between the EEC and the SP formed after the Palaeozoic. © 2004 Elsevier B.V. All rights reserved

Late Palaeozoic intra- and pericratonic basins on the East European Craton and its margins

The (Mid-) Late Devonian to Early Carboniferous was a time of widespread rifting on the East European Craton (EEC) and its margins. The most prominent basin among these and, accordingly, the best documented is the Dniepr-Donets Basin (DDB) in Ukraine and southern Russia. The DDB is associated with voluminous rift-related magmatism and broad basement uplift. Two other large, extensional, basin systems developed along the margins of the EEC at the same time: the East Barents Basin (EEB) and its onshore prolongation the Timan-Pechora Basin (TPB), and the Peri-Caspian Basin (PCB). Rifting, associated magmatism, and possible domal basement uplift are also reported elsewhere within the EEC, suggesting a common, 'active', rifting process, involving a cluster of thermal instabilities (or generalized thermal instability) at the base of the lithosphere beneath widely separated parts of the EEC by Mid-Late Devonian times. The DDB is an intracratonic rift basin, cutting across the Archaean-Palaeoproterozoic structural grain of its basement and, as such, differs from the EBB-TPB and PCB, which are pericratonic rift basins developed on reworked and juvenile crystalline basement accreted to the EEC during the Neoproterozoic. The DDB opened into a deep basin, possibly having oceanic lithospheric affinity, to the SE, in the area where it adjoins the southern PCB, suggesting the possibility that rifting led to (limited?) continental break-up in this area at this time. Post-rift compressional tectonic reactivations and basin inversion in the DDB, leading to the formation of its prominent Donbas Foldbelt segment, are related to Tethyan events (Cimmerian and Alpine orogenies) occurring on the nearby southern margin of the EEC. Post-rift compressional inversions in the PCB and TPB, which lie closer to the Urals margin of the EEC, are related to Uralian tectonics. © The Geological Society of London 2006

The evolution of the southern margin of the East European Craton based on seismic and potential field data.

This paper presents an integrated geophysical study of the southern margin of the East European Craton (EEC) in the Karpinksy Swell-North Caucasus area. It presents new interpretations of deep refraction and wide-angle reflection "deep seismic sounding" (DSS) data as well as conventional seismic and CDP profiling and new analyses of potential field data, including three-dimensional gravity and magnetic modelling. An integrated model of the physical properties and structure of the Earth's crust and, partially, upper mantle displays distinct features that are related to tectonic history of the study area. The Voronezh Massif (VM), the Ukrainian Shield and Rostov Dome (RD) of the EEC as well as the Donbas Foldbelt (DF), Karpinsky Swell (KS), Scythian Plate (SP) and Precaspian Basin (PCB) constitute the geodynamic ensemble that developed on the southern margin of the continent Baltica. There proposed evolutionary model comprises a stage of rifting during the middle to late Devonian, post-rift extension and subsidence during Carboniferous-early Permian times (synchronous with and related to the southward displacement of the Rostov Dome and extension in a palaeo-Scythian back-arc basin), and subsequent Mesozoic and younger evolution. A pre-Ordovician, possibly Riphean (?), mafic magmatic complex is inferred on a near vertical reflection seismic cross-section through the western portion of the Astrakhan Dome in the southwest part of the Precaspian Basin. This complex combined with evidence of a subducting slab in the upper mantle imply the presence of pre-Ordovician (Riphean?) island arc, with synchronous extension in a Precaspian back-arc basin is suggested. A middle Palaeozoic back-arc basin ensemble in what is now the western Karpinsky Swell was more than 100 km to the south from its present location. The Stavropol High migrated northwards, dislocating and moving fragments of this back-arc basin sometime thereafter. Linear positive magnetic anomalies reflect the position of associated faults, which define the location of the eastern segment of the Karpinsky Swell. These faults, which dip northward, are recognised on crustal DSS profiles crossing the Donbas Foldbelt and Scythian Plate. They are interpreted in terms of compressional tectonics younger than the Hercynian stage of evolution (i.e., post-Palaeozoic). © 2004 Elsevier B.V. All rights reserved