Quaternary of Norden

The Nordic countries have experienced multiple glaciations and intervening interglacials during the last ca. 2.5-3 million years. Although evidence from Greenland and Iceland shows that ice sheets started to expand some time before 3 Ma, little is known about the glaciations and intervening interglacials older than the last Glacial Maximum due to repeated phases of glacial erosion and reworking. The extensive Saalian glaciation （c. 140 ka BP） contributed to high sea levels in Greenland and in the Baltic area during the early part of the last interglacial （Eemian）. Temperatures were about 5 ℃ higher during the Eemian than they are today and the Greenland ice sheet was reduced to about half of its present size, causing globally higher sea levels than we have today. Ice extent in Fennoscandia was restricted during early Weichselian stadials, but middle Weichselian ice advances in Scandinavia reached as far as Denmark. During the Last Glacial Maximum, large ice sheets were present in all Nordic countries and coalesced with neighboring ice sheets. Deglaciation commenced around 17-15 ka BP in most areas and was promoted by rapidly rising global sea level and glacial isostasy. The Younger Dryas cold event（c. 12.6-11.5 ka BP） is seen as a short-term re-advance, still-stand or fluctuation of land-based ice sheet margins. Around 7-9 ka BP ice sheets had disappeared or had attained their present size. While uplift is still going on in some regions, others are subject to submergence. The different stages of development of the Baltic Sea are an example of how the intricare interplay between glacial eustasy and isostasy influences sedimentation, basin size and drainage patterns.     

Determination of the conduit structure in a karst aquifer based on tracer data—Lurbach system,Austria

A structure model was used to analyse solute‐transport parameter estimates based on tracer breakthrough curves. In the model system, groundwater flow is envisioned to be organised in a complex conduit network providing a variety of short circuits with relative small carrying capacities along different erosion levels. The discharge through the fully filled conduits is limited owing to void geometries and turbulent flow; thus, a hierarchic overflow system evolves where conduits are (re‐)activated or dried up depending on the flow condition. Exemplified on the Lurbach–Tanneben karst aquifer, the applicability of the model approach was tested. Information derived from multi‐tracer experiments performed at different volumetric flow rates enabled to develop a structural model of the karst network, under constraint of the geomorphological and hydrological evolution of the site. Depending on the flow rate, groundwater is divided into up to eight flow paths. The spatial hierarchy of flow paths controls the sequence of flow path activation. Conduits of the topmost level are strongly influenced by reversible alteration processes. Sedimentation or blocking causes an overflow of water to the next higher conduit. Flow path specific dissolutional denudation rates were estimated using the temporal development of the partial discharge. Copyright © 2012 John Wiley & Sons, Ltd.     

European summer temperature response to annually dated volcanic eruptions over the past nine centuries

The drop in temperature following large volcanic eruptions has been identified as an important component of natural climate variability. However, due to the limited number of large eruptions that occurred during the period of instrumental observations, the precise amplitude of post-volcanic cooling is not well constrained. Here we present new evidence on summer temperature cooling over Europe in years following volcanic eruptions. We compile and analyze an updated network of tree-ring maximum latewood density chronologies, spanning the past nine centuries, and compare cooling signatures in this network with exceptionally long instrumental station records and state-of-the-art general circulation models. Results indicate post-volcanic June–August cooling is strongest in Northern Europe 2 years after an eruption (?0.52?±?0.05 °C), whereas in Central Europe the temperature response is smaller and occurs 1 year after an eruption (?0.18?±?0.07 °C). We validate these estimates by comparison with the shorter instrumental network and evaluate the statistical significance of post-volcanic summer temperature cooling in the context of natural climate variability over the past nine centuries. Finding no significant post-volcanic temperature cooling lasting longer than 2 years, our results question the ability of large eruptions to initiate long-term temperature changes through feedback mechanisms in the climate system. We discuss the implications of these findings with respect to the response seen in general circulation models and emphasize the importance of considering well-documented, annually dated eruptions when assessing the significance of volcanic forcing on continental-scale temperature variations.     

Morpho-tectonic evolution of the Crimean mountains (Ukraine) as constrained by apatite fission track data

Apatite fission track thermochronology (AFT) is used to investigate the low-temperature thermal evolution of the Crimean Mountains and provide new insights into the geodynamic and geomorphic evolution of the westernmost tip of the Caucasus–Crimean fold-and-thrust belt. The vast majority of the samples taken from Jurassic sedimentary and magmatic rocks revealed AFT ages in the range of 51–32 Ma. These ages, together with modelled cooling paths, show that the mountain range experienced a thermal overprint after the Late Cimmerian orogeny. We interpret the overprint in terms of the burial of Cimmerian structures by a thick pile (>4 km) of platform sediments during Early Cretaceous–Late Eocene times. This scenario implies that highly elevated palaeosurfaces of Early Cretaceous age survived in large part because of the protection provided by thick accumulations of platform deposits. Since final uplift in the middle Pliocene, the palaeosurfaces have been significantly degraded and dissected by fluvial incision and large-scale landslides.     

Diamond precipitation from ascending reduced fluids in the Kaapvaal lithosphere: Thermodynamic constraints

Previous research has shown that the Kaapvaal lithospheric mantle is generally reduced and characterised by a decreasing redox state with increasing depth. As a consequence, C-O-H fluids in the Kaapvaal lithospheric mantle are dominated by H₂O, CH₄, and C₂H₆. Thermodynamic calculations demonstrate that diamond precipitation from such a fluid during ascend is possible as it is exposed to a more oxidised environment and both CH₄ and C₂H₆ are oxidised. However, the calculations also demonstrate that the diamond precipitation potential from such a fluid decreases when: (1) the mantle is either more reduced or oxidised compared to the Kaapvaal mantle, or (2) the change in temperature with pressure is smaller compared to that of the Kaapvaal mantle. Therefore, the presence of reduced mantle fluid species and a generally decreasing oxygen fugacity with increasing depth do not necessarily warrant diamond precipitation from a rising reduced fluid.     

http://www.sciencedirect.com/science/article/pii/S1674987112000631

Charnockites sensu lato（charnockite-enderbite series） are lower crustal felsic rocks typically characterised by the presence of anhydrous minerals including orthopyroxene and garnet.They either represent dry（H₂O-poor） felsic magmas that are emplaced in the lower crust or granitic intrusions that have been dehydrated during a subsequent granulite facies metamorphic event.In the first case,postmagmatic high-temperature recrystallisation may result in widespread metamorphic granulite microstructures, superimposed or replacing the magmatic microstructures.Despite recrystallisation,magmatic remnants may still be found,notably in the form of melt-related microstructures such as melt inclusions. For both magmatic charnockites and dehydrated granites,subsequent fluid-mineral interaction at intergrain boundaries during retrogradation are documented by microstructures including K-feldspar microveins and myrmekites.They indicate that a large quantity of low-H₂O activity salt-rich brines,were present（together with CO₂ under immiscible conditions） in the lower crust.     

Landslide risk analysis and its application in regional planning: an example from the highlands of the Outer Western Carpathians, Czech Republic

Using detailed field mapping, an analysis of landslide risk has been undertaken in the flysch highlands of the Outer Western Carpathians. The standardized Czech methodology of expert derived susceptibility zonation widely used for land development planning purposes and deterministic modeling of shallow landslides was used to separately assess the susceptibility of different landslide types. The two susceptibility zonation maps were used to define landslide hazard using information about landslide reactivation and the return periods of precipitation that triggered the respective landslide types. A risk matrix was then used to qualitatively analyze the landslide risk to selected assets. The monetary value of these assets, according to actual market prices, was calculated and analyzed with respect to the risk classification. Since the study area is an important residential and recreational area, the practical application of the derived results was checked through a series of interviews conducted with personnel of the local government planning and construction office. This demonstrated a willingness to apply the landslide hazard maps as well as restraints of its successful application. The main one is the absence of legally binding regulations to enforce the spatial planers to use this information.     

Limitations in the use of compound-specific stable isotope analysis to understand the behaviour of a complex BTEX groundwater contamination near Brussels (Belgium)

The application of compound-specific stable isotope analysis (CSIA) was evaluated to characterise a complex groundwater contamination. For this purpose, δ¹³C and δ²H analysis of benzenes and alkylated derivatives were used to interpret both the impact of different sources on a contaminant plume and the presence of degradation processes. The different contaminant sources could be distinguished based on their combined δ¹³C–δ²H signature of the benzene, toluene, ethylbenzene and xylenes (BTEX) dissolved in the groundwater. Despite this source differentiation, plume characterisation was not possible due to the complex mixing of the respective contaminant plumes. Furthermore, the original isotope signatures of the sources were not preserved across these plumes. To estimate the level of in situ biodegradation independently from concentration data, the Rayleigh equation was used. Although current literature identifies the application of CSIA as very promising in the frame of characterising organic groundwater pollution, this study has indicated that this approach can be limited with respect to successfully distinguish the different plumes and their relation to the known source zones.     

Sensitivity study of pulsed neutron-gamma saturation monitoring at the Altmark site in the context of CO2 storage

The injection of CO₂ into depleted natural gas reservoirs has been proposed as a promising new technology for combining enhanced gas recovery and geological storage of CO₂. During the injection, application of suitable techniques for monitoring of the induced changes in the subsurface is required. Observing the movement and the changes in saturation of the fluids contained in the reservoir and the confining strata is among the primary aims here. It is shown that under conditions similar to the Altmark site, Germany, pulsed neutron-gamma logging can be applied with limitations. The pulsed neutron-gamma method can be applied for detection and quantification of changes in brine saturation and water content, whereas changes in the gas composition are below the detection limit. A method to account for the effects of salt precipitation resulting from evaporation of residual brine is presented.     

A Frequency Matching Method: Solving Inverse Problems by Use of Geologically Realistic Prior Information

The frequency matching method defines a closed form expression for a complex prior that quantifies the higher order statistics of a proposed solution model to an inverse problem. While existing solution methods to inverse problems are capable of sampling the solution space while taking into account arbitrarily complex a priori information defined by sample algorithms, it is not possible to directly compute the maximum a posteriori model, as the prior probability of a solution model cannot be expressed. We demonstrate how the frequency matching method enables us to compute the maximum a posteriori solution model to an inverse problem by using a priori information based on multiple point statistics learned from training images. We demonstrate the applicability of the suggested method on a synthetic tomographic crosshole inverse problem.