Meteorological Observations in 1999 at the Arctic Station,Qeqertarsuaq (Godhavn), Central West Greenland/Evidence of a warmer climate around AD 600, Mittivakkat Glacier,South East Greenland

In october 1990 an automatic weather station was established at the Arctic Station (65° 15', 53°31'W), Qeqertarsuaq (Godhavn), Central West Greenland. The Station register parameters each 20 minutes, and the paramters have been described in an earlier paper in this journal by Nielsen et al.(1995). The present paper summarizes meteorological parameters during 1999.

During a field campaign in 1999, woody remains from Salix glauca were found on a nunatak, 515 m. a.s.l. on the Mittivakkat Glacier, South East Greenland. Radio carbon dating determined the age of a wood sample to AD 640. Together with analyses of macroscopic botanical remains and insect rests in peaty material found nearby, these results indicate, that a warmer climate prevailed near the glacier around AD 600. These findings are in accordance with temperature records based on studies of ice cores from the Greenland Ice sheet.     

Meteorological observations 2006 and ground temperature variations over 12-year at the Sermilik Station,Ammassalik Island,Southeast Greenland

Geografisk Tidsskrift, Danish Journal of Geography 108(1):153–161, 2008

Meteorological stations have been in operation since 1993 at the Sermilik Research Station (65°40′N, 38°10′W), Ammassalik Island, Southeast Greenland. This note presents meteorological observations for the calendar year 2006 from the two meteorological stations: Station Nunatak (515 m a.s.l.) and Station Coast (25 m a.s.l.). The year 2006 record is not complete due to a temporal break down of Station Coast (from end-of June through beginning of August). Special focus is given to ground temperature measurements at the meteorological Station Nunatak (1994–2006) 0.1 and 0.3 m below the surface. Data are presented to illustrate the intra- and inter-annual temperature variability and possible trends in the upper part of the soil.     

Accumulation of elastic strains in the upper crust on the locked transform faults and the tectonomagnetic effect

Plate tectonics only allows small deformations in the lithospheric plates. The laboratory experiments with the rock specimens show that the creep is transient when the creep strain is at most 1%. Hence, if we assume that the creep strain in the lithospheric plates is below this threshold, the creep is transient. The present paper addresses the role of the elastic, brittle (pseudo-plastic), and creep rheology of the lithosphere during the accumulation of elastic shear strains on the locked faults in the Earth’s crust, i.e., during the process of preparation of the earthquakes. The effective viscosity characterizing the transient creep is lower than that under the steady-state creep and it depends on the characteristic time of a given process. The characteristic duration of the stress and strain accumulation process in the vicinity of the locked faults is a few dozen years. On these time intervals, the thin upper crustal layer behaves as brittle; the underlying layer behaves as elastic (it is just this layer which accommodates stress accumulation leading to the earthquake), whereas the transient creep is predominant in the lower crust and mantle lithosphere. Transient creep entails nonlinear time dependence of the strains arising in the vicinity of the locked fault in the elastic crust. The perturbations in the magnetic field induced by these strains can be treated as the magnetic precursor of the earthquake.     

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.     

In situ SHRIMP U-Pb dating of monazite integrated with petrology and textures: Does bulk composition control whether monazite forms in low-Ca pelitic rocks during amphibolite facies metamorphism?

Bulk composition and specific reaction history among common silicate minerals have been proposed as controls on monazite growth in metapelitic rocks during amphibolite facies metamorphism. It has also been implied that monazite that formed during greenschist facies metamorphism may be preserved unchanged under upper amphibolite facies conditions. If correct, this would make the interpretation of monazite ages in polymetamorphic rocks exceedingly difficult, because isotopic dates could vary significantly in rocks that have experienced identical metamorphic conditions but differ only slightly in whole-rock composition. Low-Ca pelitic schists from the Mount Barren Group in southwestern Australia display a range of whole-rock compositions in AFM space and different peak mineral assemblages resulting from amphibolite facies metamorphism (∼8 kb, 650 °C). In this study, we test whether bulk composition controls the formation of monazite through geochronology and textural evidence linking monazite growth with deformation and peak metamorphism. X-ray element mapping of monazite from the metapelitic rocks reveals concentric zoning in many grains with compositionally distinct cores and rims. In situ SHRIMP U-Pb geochronology of monazite yields two ²⁰⁷Pb/²⁰⁶Pb age populations. The cores, and texturally early monazite, give an age of 1209 ± 10 Ma, interpreted to record prograde metamorphism, whereas the rims and “late” monazite define a single population of 1186 ± 6 Ma, which is considered the likely age of peak thermal metamorphism. The growth of monazite was widespread in low-Ca pelitic schists representing a broad range of compositions in AFM space, indicating that variations in bulk composition in AFM space did not control the formation of monazite during amphibolite facies metamorphism in the Mount Barren Group.     

Interaction of rhyolite melts with monazite,xenotime, and zircon surfaces

The interfacial contact region between a rhyolite melt and the accessory minerals monazite, xenotime, and zircon is investigated using molecular dynamics simulations. On all surfaces, major structural rearrangement extends about 1 nm into the melt from the interface. As evidenced by the structural perturbations in the ion distribution profiles, the affinity of the melt for the surface increases in going from monazite to xenotime to zircon. Alkali ions are enriched in the melt in contact with an inert wall, as well as at the mineral surfaces. Melt in contact with zircon has a particularly strong level of aluminum enrichment. In xenotime, the enrichment of aluminum is less than that in zircon, but still notable. In monazite, the aluminum enrichment in the contact layer is much less. It is expected that the relative surface energies of these accessory minerals will be a strong function of the aluminum content of the melt and that nucleation of zircon, in particular, would be easier for melts with higher aluminum concentration. The crystal growth rate for zircon is expected to be slower at a higher aluminum concentration because of the effectiveness of aluminum in solvating the zircon surface. The variable interfacial concentration profiles across the series of accessory minerals will likely affect the kinetics of trace element incorporation, as the trace elements must compete with the major elements for surface sites on the growing accessory minerals.