ALBERT

Description: The results of the treatment of the database on the spectrofluorometric studies of aromatic hydrocarbons (AHC) [over 500 bottom stations] allowed the authors to show the high informativity of the technique used not only for geological environmental studies but also for gaining knowledge of the genetic parameters of the organic matter. The principal spectral characteristics of the bottom sediments were established for different lithofacies groups of sediments. The results obtained, which were verified by the data of the chromatographic mass spectrometry, allow one to consider the research method developed to be suitable for multipurpose geochemical surveys.

Description: The molluscan shells from three drill and two piston cores obtained in the southern Russian sector of the Chukchi Sea are dated by the AMS 14C measurement method back to 0.8–3.5 and 9.2–10.5 ka. The period of 9–10 ka was marked by increased sedimentation rates related to the transgression onset. The fossils in the lower Holocene section exhibit the successive upward replacement of brackish-water organisms by their marine counterparts. After the opening of the Bering Strait in the middle Holocene, the sedimentation was under influence of the increased bioproductivity of the waters. The climatic optimum in the Chukotka region corresponds to the early Holocene, while the late Holocene was characterized by the wider development of the ice cover on the shelf.

Description: Although many recently published original papers and reviews deal with plant matter decomposition rates and their controls, we are still very limited in our understanding of these processes in boreal and high latitude plant communities, especially in the permafrost areas of our planet. First and foremost, this is holds true for winter periods. Here, we present the results of two years of field observations in the southern taiga and southern shrub tundra ecosystems in European Russia. We pioneered the simultaneous application of two independent methods: classic mass loss estimation by the litter-bag technique and direct measurement of CO2 emission (respiration) of the same litter bags with different types of dead plant matter. Such an approach allows us to reconstruct the intraseasonal dynamics of the decomposition rates of the main tundra litter fractions with high temporal resolution, to estimate the partial role of different seasons and fragmentation in the process of plant matter decomposition, and to determine its factors under a different temporal scale.

Description: Cruise SO258/1 of the R/V Sonne (Germany) along a route from Fremantle, Australia, to Colombo, Sri Lanka, was carried out between June 7 and July 9, 2017 for geological and biological research in the Eastern Indian Ocean. The scientific staff included 33 researchers from ten countries (Germany, Australia, USA, UK, Switzerland, France, Taiwan, Canada, Russia, Norway). Two Russian scientists participated on this cruise: O. V. Levchenko and Y. G. Marinova from the Shirshov Institute of Oceanology, Russian Academy of Sciences (IORAS), studying the problems of regional geology. This brief article provides information on geological research, which was led by the chief scientist of the cruise R. Werner, senior researcher from GEOMAR Helmholtz Centre for Ocean Research (Kiel, Germany). The complete report on the expedition is available on the GEOMAR website [4]. Cruise SO258/1 was part of the research project INGON (INDIAN–ANTARCTIC BREAK-UP ENGIMA). The main objective of the INGON project was to study the magmatic and tectonic processes that cause and accompany the breakup of continents and the formation of oceanic basins on the example of the India–Antarctica breakup about 150 Ma ago. The project is executed by the GEOMAR and the Alfred Wegener Institute (AWI) Helmholtz Centre for Polar and Marine Research (Bremerhaven). GEOMAR performed bathymetric survey and sampling of submarine rises and seamounts in the Eastern the Indian Ocean in the first “geological” leg (cruise SO258/1). AWI performed geophysical survey (magnetometry, gravimetry, multichannel seismic profiling, deep seismic sounding) in the Central Indian Basin in the second “geophysical” leg (cruise SO258/2).

Description: The paper presents data on the contents of macro- and microelements (rare earth elements included) determined in grain size fractions of the Upper Pleistocene hydrothermally altered and unaltered sediments from the Guaymas Basin (Gulf of California). Sediments subjected to high-temperature hydrothermal alteration were recovered by DSDP Hole 477A. In the finely dispersed fractions, which are mainly composed of clay minerals, alteration of the chemical composition was provoked by the hydrothermal transformation of terrigenous clay minerals. The concentration of microelements in these fractions takes place primarily at the cost of the hydrothermal finely dispersed ore minerals. Alteration of the chemical composition of the coarse-grained fractions is related to the replacement of clastogenic minerals by the secondary varieties and the formation of new minerals (including ore minerals and native metals) from the solutions. Hydrothermal alterations of the chemical composition of bulk samples depend on the degree of chemical element concentration in fractions and their content in samples.

Description: Benthic foraminiferal and sediment biogeochemical data (total organic carbon, calcium carbonate and biogenic opal contents) in two cores (1265 and 1312 m water depths) from the southeastern Sakhalin slope and one core (839 m water depth) from the southwestern Kamchatka slope were investigated to reconstruct variations of the oxygen minimum zone during the last 50 ka in the Okhotsk Sea. The oxygen minimum zone was less pronounced during the maximal cooling in the MIS 2 that is suggested to be caused by a maximal expansion of sea ice cover, decrease of marine productivity and increase of production of the oxygenated Okhotsk Sea Intermediate Water (OSIW). A two-step-like strengthening of oxygen minimum zone during the warmings in the Termination Ia and Ib was linked to (1) enhanced oxygen consumption due to degradation of large amount of organic matter in the water column and bottom sediments, originated from increased marine productivity and supply of terrigenous material from the submerged northern shelves; (2) sea ice cover retreat and reduction of OSIW production; (3) freely inflow of the oxygen-depleted deep intermediate water mass from the North Pacific.

Description: The structure of the stream network in the Lena delta has been studied, and its quantitative characteristics have been obtained for the first time. Taking into consideration the discharge of the branches as well as their width, we determined the conventional delta stream orders decreasing in a regular fashion toward the margin of the delta because of channel bifurcation. They have been used as the basis for determining the structural parameters of delta streams and studying the transformation characteristics of the flows of some materials and heat in the Lena delta.

Description: This paper presents reconstructions of ice sheet boundaries, lacustrine and marine paleobasins, as well as the connections of the Barents and Baltic seas with the North Atlantic from the Last Glacial Maximum to the Holocene. The reconstructions are based on original and published data obtained from the northern and western parts of the Barents Sea and Baltic depressions with account for the available regional schematic maps of deglaciation. The early deglaciation of the Scandinavian–Barents ice sheet culminated with the Bølling-Allerød interstadial (14.5–12.9 cal ka BP), which was characterized by a more vigorous Atlantic meridional overturning circulation (AMOC) and a corresponding increase in surface Atlantic water inflow into the Barents Sea through deep troughs. The Baltic Ice Lake (BIL) remained a dammed-up isolated basin during deglaciation from 16.0 to 11.7 cal ka BP. In the Younger Dryas (YD), the lake drained into the North Sea and was replaced by a brackish Yoldia Sea (YS) at the beginning of the Holocene (Preboreal, 11.7–10.7 cal ka BP), due to a limited connection between two basins through the Närke Strait. In the Barents Sea, the next increase in the Atlantic water influx into the deep basins corresponded to terminal YD and Preboreal events with a culmination in the Early Holocene. The Yoldia Sea became a lake again during the next stage, the Ancylus (~10.7–8.8 cal ka BP). Atlantic water inflow both into the Barents and Baltic seas varied during the Holocene, with a maximum contribution in the Early Holocene, when the Littorina Sea (LS, 8–4 cal ka BP) connection with the North Sea via the Danish Straits was formed to replace the Ancylus Lake. The recent, post-Littorina stage (PS, the last 4 cal ka) of the Baltic Sea evolution began in the Late Holocene.