Georadar Investigations of the Peretolchin Glacier (Southern Siberia)

Presented are the results obtained from radar profiling of the Peretolchin glacier in the Munku-Sardyk mountain range in the south of Siberia (June 2014 and May 2016) using georadar OKO-2 with the ABDL Triton antenna unit operating at the radiation frequency of 50 and 100 MHz. The ice thickness was determined from the profiles and the ice volumes from the cross-sectional areas and distances between profiles. The ice volume was calculated for the body of the Peretolchin glacier to be 0.007 ± 0.0019 km³. An analytical method was also used to determine the ice volume according to the type and area of glacier. It is established that the correlation between the glacier volume and area is expressed by a power function V = kS ^p . The mean ice volume, calculated with due regard for different coefficients, was 0.0061 km³. The GlabTop model that assumes the cross-sectional form of the glacier was used to infer the ice volume: the mean volume for two cross-sections (parabolic and elliptic) was 0.0073 km³. It is found that over 110 years since the start of the investigation into the morphology of the Peretolchin glacier, it has increased twice in its length and in area, its volume has decreased by a factor of 3.7, and the lower boundary of the open part of the glacier has risen 184 meters during that period.     

Conditions of the formation of plagiogranite from the Markov trough,Mid-Atlantic Ridge, 5°52′-6°02′N

Doklady Earth Sciences -     

The seawater structure of the Guyana Current and the North Equatorial Countercurrent in February–April 1990

Novel data on the kinematic and thermohaline structures of waters in the Guyana Current and the North Equatorial Countercurrent (NECC) in the winter-spring period have been obtained based on the complex hydrophysical research carried out within the economic zones of Brazil, Surinam, Barbados, and the adjacent regions. The transports of current are estimated from the results of instrumental measurements and geostrophic computations. The thermohaline characteristics of water masses are given. A bifurcation of the Guyana Current at 54–55° W is described. The results obtained are compared with those of previous research and climatic data. It is shown that the intense manifestation of the NECC at the surface is anomalous at the end of winter and early in spring.Translated by Mikhail M. Trufanov.     

Heterogeneous basement reworking during Paleoproterozoic collisional orogeny within the Belomorian province,Fennoscandian Shield

The distribution of cross-cutting and pseudoconcordant contacts of Paleoproterozoic metagabbro and their Archean host rocks were studied in the central part of the Belomorian province of the Fennoscandian Shield. It was shown that the metagabbro intrusions affected by ductile shearing during nappe stacking exhibit pseudoconcordant contact relationships. As a result of these deformations, Paleoproterozoic intrusions were sheared into boudins and tectonic slices, conformable with the nappe boundaries, while all traces of pre-Paleoproterozoic structures in the host rock complexes were obliterated. It was also shown that the original cross-cutting intrusive contacts can be still observed in intrusions unaffected by Paleoproterozoic nappe stacking. Therefore, analysis of preserved pre-Paleoproterozoic host rock structure may be helpful for reconstructing its Archean tectonic evolution. Based on the spatial distribution of localities with different contact relationships between Paleoproterozoic metagabbro and their host structure in the central part of the Belomorian province, several large domains of different tectonic styles were recognized. It was shown that these differences can be explained by heterogeneous reworking of the Archean basement during the Lapland–Kola collisional orogeny.