Investigation of the geochemical impact of CO2 on shallow groundwater: design and implementation of a CO2 injection test in Northeast Germany

A small scale and temporally limited CO₂ injection test was performed in a shallow aquifer to investigate the geochemical impact of CO₂ upon such aquifers and to apply and verify different monitoring methods. Detailed site investigation coupled with multiphase simulations were necessary to design the injection experiment and to set up the monitoring network, before CO₂ was injected over a ten-day period at three injection wells, at a depth of 18?m below surface level into a quaternary sand aquifer located close to the town of Wittstock in Northeast Germany. Monitoring methods comprised groundwater sampling and standard analyses, as well as trace element analyses and isotope analyses; geoelectrical borehole monitoring; passive samplers to analyse temporally integrated for cations and multi-parameter probes that can measure continuously for dissolved CO₂, pH and electrical conductivity. Due to CO₂ injection, total inorganic carbon concentrations increased and pH decreased down to a level of 5.1. Associated reactions comprised the release of major cations and trace elements. Geoelectrical monitoring, as well as isotope analyses and multi-parameter probes proved to be suitable methods for monitoring injected CO₂ and/or the alteration of groundwater.     

Proper motion measurements in various young stellar object jets in Taurus

We present proper motion measurements for a number of knots in the jets and bow shocks of the outflows from DG Tau, DG Tau B, T Tau, CoKu Tau 1, FS Tau, and FS Tau B in the nearby Taurus-Auriga star forming region. From these measurements and the available radial velocity data we derive tangential velocities, spatial velocities, angles of the outflows with respect to the plane of the sky, and in a couple of cases the pattern motions of the knots relative to the flow speed.     

Combination of Precise Leveling and InSAR Data to Constrain Source Parameters of the Mw = 6.5, 26 December 2003 Bam Earthquake

We used new precise leveling data acquired 40 days after the Bam earthquake in combination with radar interferometry observations from both ascending and descending orbits to investigate static deformation associated with the 2003 Bam earthquake. We invert this geodetic data set to gain insight into the fault geometry and slip distribution of the rupture. The best-fitting dislocation model is a steeply east-dipping right-lateral strike-slip fault that has a size of 11 by 8 km and strikes N2°W. We find that such smooth geometry fits available geodetic data better than previously proposed models for this earthquake. Our distributed slip model indicates a maximum strike slip of 3 m occurring about 3 to 5 km deep. The slip magnitude and depth of faulting taper to the north, where the fault approaches the Bam city. Inclusion of crustal layering increases the amount of maximum slip inferred at depth by about 4%.     

Making continental crust through slab melting: Constraints from niobium-tantalum fractionation in UHP metamorphic rutile

The formation of the continental crust (CC) is one of the most important processes in the evolution of the silicate Earth. Exactly how the CC formed is the subject of ongoing debate that focuses on its subchondritic Nb/Ta ratio. Nb and Ta are “geochemical identical twins,” so they usually do not fractionate from each other. Here, we show that rutile grains from hydrous rutile-bearing eclogitic layers recovered from drillcores in the Dabie-Sulu ultrahigh pressure terrain have highly variable Nb/Ta values (ranging from 5.4 to 29.1, with an average of 9.8 ± 0.6), indicating major fractionation of Nb and Ta most likely occurred during blueschist to amphibole-eclogite transformation in the absence of rutile. It is suggested that the released fluids with subchondritic Nb/Ta were transported to, and retained by, hydrous rutile-bearing eclogite in colder regions, resulting in suprachondritic Nb/Ta ratios for drier eclogite in hotter regions. Further dehydration of hydrous rutile-bearing eclogites cannot transfer the fractionated Nb/Ta values to the CC due to the low solubility of Nb and Ta in fluids in the presence of rutile, while dehydration-melting results in a major component of the CC, the tonalite-trondhjemite-granodiorite (TTG) component, which is responsible for the low Nb/Ta of the CC. Consequently, residual eclogites have variable but overall suprachondritic Nb/Ta.     

Book Reviews

Books reviewed:
MARSHA ALIBRANDI, GIS in the Classroom: Using Geographic Information Systems in Social Studies and Environmental Science
JO WOOD, Java Programming for Spatial Sciences     

Regional relief characteristics and denudation pattern of the western Southern Alps, New Zealand

The Southern Alps of New Zealand are the topographic expression of active oblique continental convergence of the Australian and Pacific plates. Despite inferred high rates of tectonic and climatic forcing, the pattern of differential uplift and erosion remains uncertain. We use a 25-m DEM to conduct a regional-scale relief analysis of a 250-km long strip of the western Southern Alps (WSA). We present a preliminary map of regional erosion and denudation by overlaying mean basin relief, a modelled stream-power erosion index, river incision rates, historic landslide denudation rates, and landslide density. The interplay between strong tectonic and climatic forcing has led to relief production that locally attains 2 km in major catchments, with mean values of 0.65–0.68 km. Interpolation between elevations of major catchment divides indicates potential removal of l0¹–10³ km³, or a mean basin relief of 0.51–0.85 km in the larger catchments. Local relief and inferred river incision rates into bedrock are highest about 50–67% of the distance between the Alpine fault and the main divide. The mean regional relief variability is ± 0.5 km.Local relief, valley cross-sectional area, and catchment width correlate moderately with catchment area, and also reach maximum values between the range front and the divide. Hypsometric integrals show scale dependence, and together with hypsometric curves, are insufficient to clearly differentiate between glacial and fluvial dominated basins. Mean slope angle in the WSA (ψ = 30°) is lower where major longitudinal valleys and extensive ice cover occur, and may be an insensitive measure of regional relief. Modal slope angle is strikingly uniform throughout the WSA (φ = 38–40°), and may record adjustment to runoff and landsliding. Both ψ and φ show non-linear relationships with elevation, which we attribute to dominant geomorphic process domains, such as fluvial processes in low-altitude valley trains, surface runoff and frequent landsliding on montane hillslopes, “relief dampening” by glaciers, and rock fall/avalanching on steep main-divide slopes.     

Abiotic features and macroinvertebrate colonization of the hyporheic zones of two tributaries of the river Elbe (Germany)

Whole-ecosystem experiments may reach statistical pertinence when reference and treatment sites are compared. Therefore at least two similar systems must be found. To this aim we tried to answer the question if the hyporheic zones of both streams have similar features. We postulated that both streams would be unsuitable for a comparison in an ecosystem experiment if the structure of their hyporheic invertebrate communities differs significantly. Although pH, electrical conductivity and nitrate concentration differed in the surface water, variability of all chemical criteria studied in the hyporheic zones was much lower between the two streams compared to the variability within each stream. Thus the structure of both hyporheic invertebrate communities did not differ significantly. Because of this uniformity both streams are regarded to be suitable for a comparison in a whole-ecosystem experiment.     

Cenomanian–Turonian carbonate platform deposits in west central Jordan

We studied upper Albian to Turonian shallow-marine shelf deposits (Ajlun Group) of west central Jordan along a NNE-SSW running transect. The carbonate-dominated succession includes few siliciclastic intercalations, claystones and shales, and can be subdivided into five formations. The Naur, Fuheis and Hummar Formations of upper Albian to upper Cenomanian age represent shallow subtidal to supratidal platform environments. The uppermost Cenomanian to middle Turonian Shueib Formation includes deeper water deposits of the inner/mid-shelf and locally TOC-rich black shales. Shallow-marine platform environments once again dominate the Wadi As Sir Formation (middle-upper Turonian). A new multibiostratigraphic framework is based on ammonites (mainly of the middle Cenomanian rhotomagense Zone to the middle Turonian woollgari Zone) and calcareous nannofossils (biozones CC 9–CC 11), supplemented by benthic and planktonic foraminifers and ostracods. It forms the base of a sequence stratigraphic subdivision, containing eight sedimentary sequences (S1–S8), which are separated by four Cenomanian sequence boundaries (CeJo1–CeJo4) and three Turonian sequence boundaries (TuJo1–TuJo3). This scheme allows the correlation of the platform succession from distal to proximal shelf areas in contrast to previous correlations using lithologic units. Furthermore, comparisons between the platform successions and sequence patterns of west central Jordan and those from neighbouring areas allow to differentiate local, regional, and global controlling factors of platform development within the study area.