Six new stromatolitic microbiotas from the Proterozoic of the Soviet Union

Diverse assemblages of cellularly preserved Precambrian microorganisms have been discovered in cherty stromatolitic sediments from six formations in the Soviet Union: Sukhotungusin Fm. (Middle Riphean, Siberia); Valukhtin Fm. (Middle Riphean, Siberia); Shorikha Fm. (Upper Riphean, Siberia); Minyar Fm. (Upper Riphean, Bashkiria); Olkhin Fm. (Upper Riphean, Siberia); and Chichkan Fm. (Vendian, Kazakstan). These cyanophyte-dominated microbial communities, occurring in both stratiform (cf. Stratifera) and columnar stromatolitic deposits (Baicalia hirta and Conophyton gaubitza), are the first stromatolite-building microbiotas to be reported from the Soviet Union; collectively they comprise more than one-fifth of all such Precambrian assemblages now known.     

Upscaling of Geological Models for Reservoir Simulation: Issues and Approaches

Introduction

Upscaling of Geological Models for Reservoir Simulation: Issues and Approaches     

Wide-spaced sampling of humus in fennoscandia

In support of IGCP Project 259 (International Geochemical Mapping), a pilot survey designed to test the effectiveness of analysing dried humus collected at an extremely low sampling density (one composite sample per 23 000 km²) for geochemical mapping was carried out in 49 large catchment basins in Fennoscandia. The samples were analysed for their aqua-regia leachable contents of 30 elements by ICP-ES. The results were compared with those of till sampled at the same sites and with moss from previous surveys. The correlation with underlying bedrock was also studied.Geological features exert only a weak influence on the regional distribution of elements in humus. Exceptions are high levels of Ca and Sr in areas of carbonate bedrock and low contents of K in areas of Archean rocks. The distribution patterns of Co, Cr, Cu, Mg, Ni and Zn in humus coincide partly, and the levels correlate positively with those in till. The contents of Ni, Cr and Cu are lower in humus overlying acid magmatic rocks and arkose than other rock types.Pollution is the obvious source of high concentrations of Pb, Cd and Zn in southern Sweden and southern Norway. Acid fallout seems to cause leaching of Al, P and La from the humus horizon. The contents of these elements are low in the south where deposition of S and N is high and pH of rainwater is below 4.5. Deposition of sea salts gives high levels of Na, Mg, K and B along the coast of Norway and southern Sweden.The contents of several elements in humus correlate positively with the amount of organic matter (LOI). Comparison between four types of forest shows that the contents of Ca, Mg and Na in birch forest and of Cd, Mn, Pb and Zn in spruce forest are significantly higher than in other forest types. These features, however, are considered false and are due to sources such as atmospheric deposition of anthropogenic metals and sea salt.The results of the relatively strong chemical attack used for analyses of humus samples are less informative than those from till and overbank sediments. A weaker attack may have given more useful information. The humus horizon could be suited for environmental monitoring if used in global geochemical mapping.     

Comparison between hydroacoustical and terrestrial evidence of glacially induced faulting,Lake Voxsjön,central Sweden

International Journal of Earth Sciences - The recent availability of a terrestrial high-resolution digital elevation model in Sweden has led to the discovery of previously unknown scarps believed...     

Assessment of marine benthic quality change in gradients of disturbance: Comparison of different Scandinavian multi-metric indices

Three multi-metric benthic macrofauna indices were used to assess marine benthic ecological quality status (EcoQS) according to the European Water Framework Directive, in seven pollution gradients mainly, western Scandinavia. The impacts included organic load, hypoxia, metals, urban effluents and physical disturbance. The indices responded in a similar threshold fashion, irrespective of impact factor identity. Usually, the border between Good and Moderate EcoQS (G/M), is determined as some deviation from a reference situation. References, however, are difficult to find. An alternative procedure is described to estimate the G/M border, not requiring reference data. Thresholds, where faunal structure deterioration commences, were identified from non-linear regressions between indices and impact factors. Index values from the less impacted side of the thresholds were assumed to come from environments of Good and High EcoQS, and the 5th percentile of these data, was defined as the G/M border. Estimated G/M borders compared well with previous studies.     

The Rainstorm of August 1998 in the Abisko Area, Northern Sweden: Preliminary Report on Observations of Erosion and Sediment Transport

Several rainstorms with strong erosional effects have been recorded in Scandinavia during recent decades. The erosion occurs by the release of rapid mass movements on mountain slopes or through fluvial incision and bank collapse along streams and rivers. Various factors, such as terrain characteristics and seasonal timing of the rainstorm event, are thought to favour the predominance of either of the two types of erosion for particular events. A new example of this variable impact of rainstorms is briefly described, and related research issues are outlined.     

Impact of acid sulfate soils on the geochemistry of rivers in south-western Finland

Large areas of acid sulfate (AS) soils are located along the coastal plains of Finland, and previous studies have shown that after reclamation they release extreme quantities of metals to watercourses in mid-western and northern Finland. In this study on streams of south-western Finland, where little information about AS soils is available, these soils were found to exhibit the same pattern of elevated metal- and sulfate concentrations as in the notorious AS soil landscapes of mid-western Finland. Meteorologically/hydrologically driven temporal variations of these elements were great in the most affected streams. There were also significant positive implications regarding future environmental work; AS soils in the highlighted region were found to cause sudden temporal influxes of acidic water only in the most affected streams, indicating that the overburden and soils of the area discharge well buffered water. Moreover, it was indicated that the high (less toxic) metal concentrations are largely caused by erosion of suspended phyllosilicates (<0.45 μm) from farmland rather than by AS soils.     

Late-orogenic Svecofennian deformation in SW Finland constrained by pegmatite emplacement ages

Late stages of the Svecofennian orogeny in SW Finland were related to a tranpressional stress field and dextral movements along crustal scale shear zones under decreasing temperature and pressure conditions. In the Kemiö area, a minimum estimate for the time span of movements along one of these shear zones is obtained from the ages of 1840 to 1830 Myr-old microcline granite sheets, related to early ductile deformation, and by dating structurally late rare-mineral granite pegmatites, related to brittle deformation. One pegmatite was emplaced when the rheological conditions in the gabbro changed from ductile to semi-ductile and brittle. It has U-Pb ferrotapiolite ages ranging between 1807.0 ± 2.9 Myr (2 ) and 1803.1 + 2.9/ -2.0 Myr (2 ). Another pegmatite emplaced under brittle conditions has an U-Pb ferrotapiolite age of 1802.9 ± 1.3 Myr (2 ). These pegmatites were emplaced preferentially in gabbroic rocks, that showed brittle to semi-ductile deformation at a time when their more felsic host-rocks still showed ductile deformation. The age range bracketed by the microcline granite sheets and the structurally late pegmatites indicates that ductile deformation related to the transpressional Late Svecofennian tectonic regime in southwestern Finland, persisted for at least 30–40 Myr.