Biostratigraphic significance of the calcareous nannofossil genus Reticulofenestra in the Upper Pliocene of the North Atlantic

We demonstrate size fluctuations of the calcareous nannofossil genus Reticulofenestra in Upper Pliocene sediments from the North Atlantic Ocean and clarify a characteristic evolutionary trend of this genus. Four bioevents, which are based on abrupt decreases in maximum size and on changes of morphologic features of Reticulofenestra specimens, are detected in the sediments. They are the disappearance of R. minutula var. A, the termination of Acme Zone II of R. minutula var. C, the disappearance of R. minutula var. B, and the termination of Acme Zone I of R. minutula var. C, in ascending order. These are nearly synchronous and traceable events.

Partial pressure of carbon dioxide along the Transatlantic section from 7 November till 19 December 2000

Along a transatlantic section from 57°N to 60°S that was carried out from November 7 till December 19, 2000 on board R/V Horizont II concentrations of CO2 were measured in the near-water layer of the air and differences between partial pressures in water and air in various climatic zones were calculated. It was shown that variations of CO2 concentrations in the near-water layer of air and those of values of water-air partial pressure difference were from 324x10**-6 to 426x10**-6 and from 150x10**-6 to 100x10**-6 atm, respectively. Maximum value of CO2 partial pressure in air in the near-water layer (426x10**-6 atm) was noted at 45°-47°N; minimum of 324x10**-6 atm was found in Antarctica at 59°S. During measurenents maximum value of CO2 partial pressure difference in water and air (150 x10**-6) was observed at 45°-48°N; maximum flux in this case was directed from the atmosphere to water. Maximum value of CO2 partial pressure difference in water and air for flux directed from the ocean to air (100 x10**-6) was observed at 59°-60°S. Comparison of calculated values of partial pressure difference in water and air with previous data points to more intense exchange of CO2 between the ocean and atmosphere during the survey period was considered. According to values of CO2 partial pressure difference in air and water as compared to 1975, exchange intensity in the Northern Hemisphere (absorption from the atmosphere) increased. A well-pronounced latitudinal effect of distribution of CO2 partial pressure in air was observed. Along the route variations in CO2 concentrations in zones of water divergence and convergence were registered.

Analysis of soils from King George Island and Casey station, Antarctica

A comparative study was carried out on soils of the maritime (Arctowski, King George Island) and the continental (Casey, Wilkes Land) Antarctic. Soil sampIes are described for surface layers (0-10 cm) by their in situ temperature profiles as well as by field and laboratory analyses of grain sizes, pH and nutrient contents. Active cryoturbation is a main factor of mixing processes in surfaces with high silt and clay content. In both regions processes of podzolisation were recognized. Microclimatic conditions show the importance of small scale processes which are of special importance for freeze-thaw cycles. The distribution of nutrients and other inorganic components is rather homogeneous in regosols and leptosols. But in soils with organic top layers by lichen and moss cushions (crusts) accumulation occurs as well as displacement of metal ions into deeper layers (>10 cm). Histosols show patterns of brown soils. Special attention is given to the origin of nitrogen compounts and the different ways of import of other components (e.g. chloride) into the Antarctic system are discussed.

Lavas from the Elbrus volcano, Greater Caucasus

Comprehensive geochronological and isotope-geochemical studies showed that the Late Quaternary Elbrus Volcano (Greater Caucasus) experienced long (approximately 200 ka) discrete evolution with protracted periods of igneous quiescence (approximately 50 ka) between large-scale eruptions. Volcanic activity of Elbrus is subdivided into three phases: Middle Neopleistocene (225-170 ka), Late Neopleistocene (110-70 ka), and Late Neopleistocene - Holocene (earlier than 35 ka). Petrogeochemical and isotope (Sr-Nd-Pb) signatures of Elbrus lavas point to their mantle-crustal origin. It was shown that hybrid parental magmas of the volcano formed due to mixing and/or contamination of deep-seated mantle melts by Paleozoic upper crustal material of the Greater Caucasus. Mantle reservoir that participated in genesis of Elbrus lavas as well as most other Neogene-Quaternary magmatic rocks of Caucasus was represented by the lower mantle "Caucasus" source. Primary melts generated by this source in composition corresponded to K-Na subalkali basalts with the following isotopic characteristics: 87Sr/86Sr = 0.7041+/-0.0001, e-Nd = +4.1+/-0.2, 147Sm/144Nd = 0.105-0.114, 206Pb/204Pb = 18.72, 207Pb/204Pb = 15.62, and 208Pb/204Pb = 38.78. Temporal evolution of isotope characteristics for lavas of the Elbrus Volcano is well described by a Sr-Nd mixing hyperbole between "Caucasus" source and estimated average composition of the Paleozoic upper crust of the Greater Caucasus. It was shown that, with time, proportions of mantle material in parental magmas of Elbrus gently increased: from ~60% at the Middle-Neopleistocene phase of activity to ~80% at the Late Neopleistocene - Holocene phase, which indicates an increase of activity of a deep-seated source at decreasing input of crustal melts or contamination with time. Unraveled evolution of the volcano with discrete eruption events, lacking signs of cessation of the Late Neopleistocene - Holocene phase, increasing contribution of the deep-seated mantle source in genesis of Elbrus lavas with time as deduced from isotope-geochemical data, as well as numerous geophysical and geological evidence indicate that Elbrus is a potentially active volcano and its eruptions may be resumed. Possible scenarios were proposed for evolution of the volcano, if its eruptive activity continued.

Satellite image map of King George Island, Antarctica

A new topographic database for King George Island, one of the most visited areas in Antarctica, is presented. Data from differential GPS surveys, gained during the summers 1997/98 and 1999/2000, were combined with up to date coastlines from a SPOT satellite image mosaic, and topographic information from maps as well as from the Antarctic Digital Database. A digital terrain model (DTM) was generated using ARC/INFO GIS. From contour lines derived from the DTM and the satellite image mosaic a satellite image map was assembled. Extensive information on data accuracy, the database as well as on the criteria applied to select place names is given in the multilingual map. A lack of accurate topographic information in the eastern part of the island was identified. It was concluded that additional topographic surveying or radar interferometry should be conducted to improve the data quality in this area. In three case studies, the potential applications of the improved topographic database are demonstrated. The first two examples comprise the verification of glacier velocities and the study of glacier retreat from the various input data-sets as well as the use of the DTM for climatological modelling. The last case study focuses on the use of the new digital database as a basic GIS (Geographic Information System) layer for environmental monitoring and management on King George Island.