Determination of Postglacial Land Uplift in Fennoscandia from Leveling, Tide-gauges and Continuous GPS Stations using Least Squares Collocation

Precise leveling, tide-gauge recordings and time series from continuous GPS stations are all sources of information about the ongoing postglacial land uplift in Fennoscandia. This article describes how to gather these three sources of data together in a least-squares collocation adjustment in order to calculate uplift rates, as well as new heights for the benchmarks in the leveling network. The estimated reliability of the resulting uplift model is in general better than 0.4 mm/year, decreasing in areas of fewer data.A smoother and extended version of the land uplift model described here is used in the adjustment of the new height system in Sweden (RH 2000) under the name RH 2000 LU. Later on, the name was changed to NKG2005LU. The Finnish Geodetic Institute (FGI) has decided to use the same model when they calculate their new height system, N2000.     

Multicollinearity in cross-sectional regressions

The paper examines robustness of results from cross-sectional regression paying attention to the impact of multicollinearity. It is well known that the reliability of estimators (least-squares or maximum-likelihood) gets worse as the linear relationships between the regressors become more acute. We resolve the discussion in a spatial context, looking closely into the behaviour shown, under several unfavourable conditions, by the most outstanding misspecification tests when collinear variables are added to the regression. A Monte Carlo simulation is performed. The conclusions point to the fact that these statistics react in different ways to the problems posed.     

Observation of DMSO and CH3S(O)OH from the gas phase reaction between DMS and OH

Products and mechanisms have been investigated for the reactions between dimethylsulfide (DMS) and dimethylsulfoxide (DMSO) and the hydroxyl radical (OH) in the presence of NO_x. All of the experiments were performed in a 480 L reaction chamber, applying Fourier transform infrared spectroscopy (FT-IR) and ion chromatography as the analytical techniques.In addition to the sulfur containing products that are known to be produced from the gas phase reaction between DMS and OH (SO₂, dimethylsulfone, methylsulfonyl peroxynitrate, methanesulfonic acid, H₂SO₄), DMSO and methanesulfinic acid (CH₃S(O)OH) were also observed as products. Only SO₂, DMSO₂ and methylsulfonyl peroxynitrate were found as sulfur containing products in the reaction between DMSO and OH. Based on these new results we propose a mechanism for the atmospheric oxidation of DMS and DMSO by OH radical.     

Trace element partitioning and melt structure: An experimental study at 1 atm pressure

Diopside-melt and forsterite-melt rare earth (REE) and Ni partition coefficients have been determined as a function of bulk compositions of the melt. Available Raman spectroscopic data have been used to determine the structures of the melts coexisting with diopside and forsterite. The compositional dependence of the partition coefficients is then related to the structural changes of the melt.The melts in all experiments have a ratio of nonbridging oxygens to tetrahedral cations ($\text{NBO}\text{T}$) between 1 and 0. The quenched melts consist of structural units that have, on the average, 2 (chain), 1 (sheet) and 0 (three-dimensional network) nonbridging oxygens per tetrahedral cation. The proportions of these structural units in the melts, as well as the overall $\text{NBO}\text{T}$, change as a function of the bulk composition of the melt.It has been found that Ce, Sm, Tm and Ni crystal-liquid partition coefficients ($\text{K}{}^{\mathrm{crystal?liq}}{}_{\mathrm{i}}\text{=}\text{C}{}^{\mathrm{crystal}}{}_{\mathrm{i}}\text{C}{}^{\mathrm{liq}}{}_{\mathrm{i}}$) decrease linearly with increasing $\text{NBO}\text{T}$. The values of the individual REE crystal-liquid trace element partition coefficients have different functional relations to $\text{NBO}\text{T}$, so that the degree of light REE enrichment of the melts would depend on their $\text{NBO}\text{T}$.The solution mechanisms of minor oxides such as CO₂, H₂O, TiO₂, P₂O₅ and Fe₂O₃ in silicate melts are known. These data have been recast as changes of $\text{NBO}\text{T}$ of the melts with regard to the type of oxide and its concentration in the melt. From such data the dependence of crystal-liquid partition coefficients on concentration and type of minor oxide in melt solution has been calculated.     

Radioelement (U,Th, Rn) concentrations in Norwegian bedrock groundwaters

Twenty-eight samples of groundwater from bedrock boreholes in three distinct Norwegian geological provinces have been taken and analyzed for content of Rn, U, and Th, together with a wide variety of minor and major species. Median values of 290 Bq/1, 7.6 g/1, and 0.02 g/1 were obtained for Rn, U, and Th respectively, while maximum values were 8500 Bq/1, 170 g/1, and 2.2 g/1. Commonly suggested drinking water limits range from 8 to 1000 Bq/1 for radon and 14 to 160 g/1 for uranium. Radioelement content was closely related to lithology, the lowest concentrations being derived from the largely Caledonian rocks of the Trøndelag area, and the highest from the Precambrian Iddefjord Granite of southeast Norway (11 boreholes) where median values of 2500 Bq/1, 15 g/1 and 0.38 g/1, respectively, were obtained. The Iddefjord Granite is not believed to be unique in Norway in yielding high dissolved radionuclide contents in groundwaters, and several other granitic aquifers warrant further investigation in this respect.     

Mildly peraluminous high-silica granites in a continental rift: the Drammen and Finnemarka batholiths,Oslo Rift,Norway

The peraluminous Drammen batholith (650 km²) is the largest granite complex within the mainly alkaline province of the Permo-Carboniferous Oslo Rift, and peraluminous to metaluminous granites are also present in the southern part of the otherwise alkaline Finnemarka complex (125 km²). The emplacement of the Drammen granite, and probably most of the other biotite granite complexes, predate the alkaline syenites and granites. The eight separate petrographic types of the Drammen batholith range in SiO₂ from 70 to 79 wt.% and have experienced variable amounts of fractionation of feldspars, biotite, zircon, apatite, titanite and Fe–Ti-oxides. The initial Sr, Nd and Pb isotopic ratios and a decoupling between the variations in the SiO₂ content and the aluminum saturation index [ASI=Al₂O₃/(CaO+Na₂O +K₂O)] show that the various intrusive phases are not strictly comagmatic. The _Nd values of the southern part of Finnemarka (+3.5 to +4) and the northern part of the Drammen granite (+1 to +1.5) are high and indicate insignificant (for Finnemarka) to minor Precambrian crustal or enriched mantle contributions. The very low _Sr values of all of these samples (–1 to –12, outside the main Oslo Rift magmatic array), point to a time integrated Rb-depleted crustal contaminant or an EM1 mantle component. The earliest extruded alkali basalts along the southwestern margin of the Oslo Rift are the only other samples within this low _Sr area, but their isotopic signature may also be linked to a mantle enrichment event (involving an EM1 component), e.g. associated with the Fen carbonatite magmatism 540 Ma ago. For a given ²⁰⁶Pb/²⁰⁴Pb, the ²⁰⁸Pb/²⁰⁴Pb ratios of the Drammen and Finnemarka batholiths are distinctly lower than those of the Skien alkaline volcanics and all other magmatic Oslo Rift rocks. This may indicate that the lithosphere of the central part of the rift had a time integrated Th-depletion. The samples from the southern part of the Drammen batholith, characterized by the presence of abundant miarolitic cavities, have _Nd near 0 (–0.7 to +0.4) but strongly elevated _Sr of +35 to +67. The combined Pb isotopic ratios of all the samples analyzed indicate that the Precambrian crustal anatectic contribution is in the form of time integrated Th-and U-depleted lower crust, and the high +_Sr of the sourthern part of the Drammen granite results from shallow level wallrock assimilation or magma-fluid interactions. The remarkably low contribution of old crustal components to the Finnemarka and the northernmost Drammen batholiths may result from extensive late Precambrian intracustal differentiation in southwestern Scandinavia, leading to widespread upper crustal granites ( 900 Ma) and a correspondingly dense and refractory lower crust, in particular in a zone intersecting the central part of the rift. Liquidus phase relations and mass-balance constrainst permit derivation of the granites from mildly alkaline to tholeiitic melts by extensive crystal fractionation of clinopyroxene-and amphibole-rich assemblages. It is equally possible to form the granitic magmas by partial melting of Permian gabbros of similar composition. Either scenario is consistent with the isotopic constrainst and with the presence of dense cumulates and/or residues in the lower crust. The lack of igneous rocks of intermediate composition associated with the Drammen and Finnemarka batholiths point to an efficient upper crustal density filtering. Considerable amounts of heat would be accumulated in this region if differentiated, intermediate melts could not escape to shallower levels. Successive magma injections would therefore easily result in partial melting of already solidified mafic to intermediate melts and cumulates, and it is suggested that the peraluminous granites formed mainly by water-undersaturated anatexis of mafic material.     

Direct 40Ar/39Ar dating of Late Ordovician and Silurian brittle faulting in the southwestern Norwegian Caledonides

Structural data as well as U–Pb zircon and ⁴⁰Ar/³⁹Ar biotite and muscovite ages were collected from the Rolvsnes granodiorite in western Norway. The granodiorite intruded at c. 466 Ma, cooled quickly and escaped later viscous deformation. Brittle top‐to‐the‐NNW thrust faults (Set I) and WNW–ESE striking dextral strike‐slip faults (Set II) formed in a NNW–SSE transpressional regime. ⁴⁰Ar/³⁹Ar dating of synkinematic mica from both sets reveals a c. 450 Ma (Late Ordovician) age of faulting, which constrains early‐Caledonian brittle deformation. Set I and II faults are overprinted by a set of lower‐grade, variably oriented chlorite‐ and epidote‐coated faults (Set III) constraining WNW–ESE shortening. A lamprophyric dyke oriented compatibly with this stress field intruded at c. 435 Ma (Silurian), indicating that Set III formed at the onset of the Scandian Baltica–Laurentia collision. The preservation of Caledonian brittle structures indicates that the Rolvsnes granodiorite occupied a high tectonic level throughout the Caledonian orogeny.     

Redox Chemistry in the Root Zone of a Salt Marsh Sediment in the Tagus Estuary,Portugal

Measurements of O₂, Fe(II), Mn(II)and HS₅ in salt marshsediments in the Tagus Estuary, Portugal, made with a voltammetric microelectrode, reveal strong seasonal differences in pore water composition within the 20~cm deep root zone. In spring, oxygen was below detection limit except close to the sediment surface. Fe(II) was present below 5 cm in concentrations ranging from detection limit to 1700 M. In summer, oxygen was present in the pore water almost to the bottom of the root zone in concentrations ranging from detection limit to more than 100 M. The spatial variability was intense: O₂ concentrations as high as 78 M and as low as 25 M existed within 2~mm of each other. Fe(II) was below detection limit except towards the bottom of the root zone. In late fall, oxygen was found to 8 cm depth, but in concentrations lower than in summer, and Fe(II) was present below 9 cm. Mn(II) was found at levels declining from typical values of 200 M in spring to less than 20 M in late fall. With one exception, sulfide was below the detection limit in all measurements. During periods when dissolved Fe(II) is available in the pore water at the same time as ₂ is delivered by roots, iron-rich concretions can form on roots. These conditions, which lead to precipitation of iron oxide in the sediment adjacent to roots, exist in spring, when new roots infiltrate anoxic Fe(II) containing sediment. They do not exist in summer, when dissolved Fe(II) is unavailable, or in winter, when oxygen is unavailable. The seasonal redox pattern revealed by the pore water chemistry is driven by the annual cycle of growth and decay of roots.