Investigating the amount of zeroing in modern sediments of River Danube, Austria

Sediments attributed to flooding events of River Danube concerning the bleaching of the optical stimulated luminescence (OSL) signal were investigated. It is demonstrated that the OSL signal in both quartz and feldspar is not completely but differentially bleached in the sediment grains. Partial bleaching of the samples is clearly indicated by the scatter of equivalent dose determined for several individual single aliquots. It is also shown that residual ages in feldspars are significantly higher than those calculated for quartz. It is furthermore demonstrated that analysing measurement-time dependent equivalent dose estimates is not a suitable method to identify partial bleaching in the investigated sediment grains. However, the transport and deposition process of the investigated samples was probably disturbed by an artificial input of sediment, and this case study may thus not be representative of undisturbed high flood events in the past.     

The abundance and radial distribution of satellite galaxies

Using detailed mock galaxy redshift surveys (MGRSs) we investigate the abundance and radial distribution of satellite galaxies. The mock surveys are constructed using large numerical simulations and the conditional luminosity function (CLF), and are compared against data from the Two Degree Field Galaxy Redshift Survey (2dFGRS). We use Monte Carlo Markov chains to explore the full posterior distribution of the CLF parameter space, and show that the average relation between light and mass is tightly constrained and in excellent agreement with our previous models and with that of Vale & Ostriker. The radial number density distribution of satellite galaxies in the 2dFGRS reveals a pronounced absence of satellites at small projected separations from their host galaxies. This is (at least partly) owing to the overlap and merging of galaxy images in the 2dFGRS parent catalogue. Owing to the resulting close-pair incompleteness we are unfortunately unable to put meaningful constraints on the radial distribution of satellite galaxies; the data are consistent with a radial number density distribution that follows that of the dark matter particles, but we cannot rule out alternatives with a constant number density core. Marginalizing over the full CLF parameter space, we show that in a ΛCDM concordance cosmology the observed abundances of host and satellite galaxies in the 2dFGRS indicate a power spectrum normalization of  σ₈≃ 0.7  . The same cosmology but with  σ₈= 0.9  is unable to match simultaneously the abundances of host and satellite galaxies. This confirms our previous conclusions based on the pairwise peculiar velocity dispersions and the group multiplicity function.     

History and sand budgets of the barrier island system in the Panama City,Florida, region

Shell Island and Crooked Island peninsulas comprise the Holocene barrier system in the Panama City, Florida, region. Both of these peninsulas have experienced a history of integration-fragmentation-integration superimposed on a net shoreward migration since 1779. Catastrophic events such as hurricanes are most probably responsible for the pass cutting which has fragmented these barriers. Both barrier peninsulas have very nearly segmented St. Andrew Sound into an eastern and western portion. This segmentation has been achieved through natural causes in the eastern or Crooked Island region, but an alternation in the tidal return pattern, effected by the cutting of a canal across Shell Island, is probably responsible for the ongoing segmentation of the western portion.Rates of erosion/deposition, determined by comparing bathymetries charted in 1877, 1930, and 1946, demand that these two peninsulas receive material by eastward transport. Furthermore, the long shore drift of both peninsulas is bidirectional, northwesterly and southeasterly. These two drift components are very nearly equal in magnitude immediately west of Shell Island; net easterly drift occurs on Shell Island peninsula. Crooked Island experiences net westerly and easterly drift; the easterly drift terminates in the Bell Shoal area and does not reach the adjacent St. Joe Spit.     

The dissolved Beryllium isotope composition of the Arctic Ocean

We present the first comprehensive set of dissolved ¹⁰Be and ⁹Be concentrations in surface waters and vertical profiles of all major sub-basins of the Arctic Ocean, which are complemented by data from the major Arctic rivers Mackenzie, Lena, Yenisey and Ob. The results show that ¹⁰Be and ⁹Be concentrations in waters below 150 m depth are low and only vary within a factor of 2 throughout the Arctic Basin (350-750 atoms/g and 9-15 pmol/kg, respectively). In marked contrast, Be isotope compositions in the upper 150 m are highly variable and show systematic variations. Cosmogenic ¹⁰Be concentrations range from 150 to 1000 atoms/g and concentrations of terrigenous ⁹Be range from 7 to 65 pmol/kg, resulting in ¹⁰Be/⁹Be ratios (atom/atom) between 0.5 and 14 × 10⁻⁸. Inflowing Atlantic water masses in the Eurasian Basin are characterized by a ¹⁰Be/⁹Be signature of 7 × 10⁻⁸. The inflow of Pacific water masses across the Bering Strait is characterized by lower ratios of 2-3 × 10⁻⁸, which can be traced into the central Arctic Ocean, possibly as far as the Fram Strait. A comparison of the high dissolved surface ¹⁰Be and ⁹Be concentrations (corresponding to low ¹⁰Be/⁹Be signatures of ∼2 × 10⁻⁸) in the Eurasian Basin with hydrographic parameters and river data documents efficient and rapid transport of Be with Siberian river waters across the Siberian Arctic shelves into the central Arctic Basin, although significant loss and exchange of Be on the shelves occurs. In contrast, fresh surface waters from the Canada Basin also show high cosmogenic ¹⁰Be contents, but are not enriched in terrigenous ⁹Be (resulting in high ¹⁰Be/⁹Be signatures of up to 14 × 10⁻⁸). This is explained by a combination of efficient scavenging of Be in the Mackenzie River estuary and the shelves and additional supply of cosmogenic ¹⁰Be via atmospheric fallout and melting of old sea ice. The residence time of Be in the deep Arctic Ocean estimated from our data is 800 years and thus similar to the average Be residence time in the global ocean.     

Uncertainties of geochemical modeling during CO<Subscript>2</Subscript> sequestration applying batch equilibrium calculations

One of the uncertainties in the field of carbon dioxide capture and storage (CCS) is caused by the parameterization of geochemical models. The application of geochemical models contributes significantly to calculate the fate of the CO₂ after its injection. The choice of the thermodynamic database used, the selection of the secondary mineral assemblage as well as the option to calculate pressure dependent equilibrium constants influence the CO₂ trapping potential and trapping mechanism. Scenario analyses were conducted applying a geochemical batch equilibrium model for a virtual CO₂ injection into a saline Keuper aquifer. The amount of CO₂ which could be trapped in the formation water and in the form of carbonates was calculated using the model code PHREEQC. Thereby, four thermodynamic datasets were used to calculate the thermodynamic equilibria. Furthermore, the equilibrium constants were re-calculated with the code SUPCRT92, which also applied a pressure correction to the equilibrium constants. Varying the thermodynamic database caused a range of 61% in the amount of trapped CO₂ calculated. Simultaneously, the assemblage of secondary minerals was varied, and the potential secondary minerals dawsonite and K-mica were included in several scenarios. The selection of the secondary mineral assemblage caused a range of 74% in the calculated amount of trapped CO₂. Correcting the equilibrium constants with respect to a pressure of 125 bars had an influence of 11% on the amount of trapped CO₂. This illustrates the need for incorporating sensitivity analyses into reaction pathway modeling.     

Uncertainty and asymmetric information: An overview

This paper provides an overview of the literature on fisheries economics related to uncertainty and asymmetric information. It is argued that uncertainty is relevant in connection with present and future stock sizes and prices, while asymmetric information is important for cost functions, catches, catch per unit of effort, and effort. The literature on uncertainty and asymmetric information can be seen as providing the basis of an argument for using taxes in fisheries management. It is, therefore, surprising that over 55 countries regulate their fisheries with individual quotas, while taxes are not used at all.     

Multiple mantle sources during island arc magmatism: U–Pb and Hf isotopic evidence from the Kohistan arc complex, Pakistan

ABSTRACT This paper presents high-precision U–Pb ages and initial Hf isotopic compositions of zircon from mafic to felsic rocks of the Kohistan Arc Complex, Pakistan. Three magmatic pulses tapping geochemically different reservoirs are distinguished. Partial melting of mantle with MORB-type isotopic characteristics generated 99–92-Ma-old magmas. Plutonism around 85 Ma tapped a more fertile mantle source, most likely consisting of a >600-Ma-old metasomatically enriched mantle, or of mantle contaminated by an old sedimentary component; 82-Ma-old felsic peraluminous dykes have MORB-type isotopic compositions considered to be inherited from remelting earlier magmas in the deep base of the arc. The isotopic results demonstrate several and rather rapid changes in melt source region during arc development. They also show that there was subordinate continental influence and negligible importance of slab components for the Hf budget during the generation of the Kohistan Arc Complex.