Sanchez-Garcia L.,University of Stockholm |
Cato I.,Geological Survey of Sweden |
Gustafsson O.,University of Stockholm
Marine Chemistry | Year: 2010
A growing literature proposes that combusted-derived black carbon (BC) dominates the sorption and, by inference, the environmental distribution and bioavailability of many hydrophobic pollutant classes. There is a paucity of studies simultaneously evaluating the distribution of both BC geosorbents and pollutant sorbates in the actual field. Here, 120 surface sediments collected by the Geological Survey of Sweden along the 2000 km continental shelf along the Swedish coast facilitated evaluation of the relative influences of BC and non-BC organic carbon (OC) on the spatial distribution of polycyclic aromatic hydrocarbons (PAHs). The sum of 15 out of the 16 EPA PAHs ranged from 0.12 to 9.6 μg/g dry weight (dw), with the highest levels being found in the southern half of the Swedish Shelf (SS) area and in the vicinity of larger cities (Stockholm, Göteborg, Malmö and Umeå). Source-diagnostic PAH ratios such as ANT/(PHE + ANT), FLT/(FLT + PYR), BaA/(BaA + BPE), IPY/(IPY + BPE), CombPAH/ΣPAH and LMW/HMW suggested that pyrogenic sources are dominating the load of PAHs in Swedish Baltic and North Sea sediments. The sediment TOC was 4.8-168 mg/gdw (median 43 mg/gdw), while a BC concentration of 0.6-18 mg/gdw (median 1.8 mg/gdw) yielded BC:TOC ratios spanning a wide range of 1.7-47% (median 4.6%). Empirical distribution function tests indicated that the use of linear regression statistics was inappropriate. Instead, evaluation with the non-parametric Spearman function yielded higher correlation coefficient (rS) for total PAHs versus BC (0.54, p < 0.01) than versus either TOC (0.28, p < 0.01) or OC (TOC-BC; 0.26, p < 0.01). The results from this field study, encompassing an order of magnitude more observations than any previous sediment study, constitute a broad field manifestation of the importance of BC in affecting the distribution of planar aromatic pollutants in aquatic environments. © 2009 Elsevier B.V. All rights reserved.
Smith C.A.,Geological Survey of Sweden |
Sundh M.,Geological Survey of Sweden |
Mikko H.,Geological Survey of Sweden
International Journal of Earth Sciences | Year: 2014
In Sweden, knowledge of the location and timing of glacially induced faulting and seismicity is critical to effective engineering of a long-term nuclear disposal facility. To improve understanding and modeling of the complex ice-induced and tectonic stresses associated with glacially induced faulting, field studies detailing the location and timing of movement of such structures are required. Although the fault has not been confirmed in the bedrock, multi-proxy surficial geologic evidence indicates that the recently discovered scarp in Bollnäs is such a structure. Machine-excavated trenches across the scarp reveal landsliding down the scarp and, in one location, faulted and vertically offset fine-grained glacial sediments. The presence of water-escape structures in trenches excavated on a topographic high strongly suggests a co-seismic origin derived from earthquake magnitudes >5.5. Numerous landslides in till exist in the region as well. Four slopes with landslides were examined in detail, and the factors of safety for these slopes indicate stable conditions and suggest a seismic trigger. Basal radiocarbon dates from peat bogs located stratigraphically above the landslides provide minimum limiting ages for the co-seismic landslides. The oldest date indicates sliding prior to 10,180 calendar years before the present. The proposed Bollnäs Fault is 400 km south of the so called Lapland Fault Province. To date, it is the southernmost confirmed glacially induced fault in Sweden. The results of this study are consistent with existing modeling results that indicate fault instability in this region of central Sweden following deglaciation. © 2014 Springer-Verlag Berlin Heidelberg.
Reinholdsson M.,Lund University |
Snowball I.,Lund University |
Snowball I.,Uppsala University |
Zillen L.,Geological Survey of Sweden |
And 2 more authors.
Earth and Planetary Science Letters | Year: 2013
Magnetotactic bacteria (MTB) are known to biosynthesise single-domain magnetite (Fe3O4) for geomagnetic navigation and their relict magnetosomes (called magnetofossils) can control the magnetic properties of lake and marine sediments. Magnetotactic bacteria also produce greigite (Fe3S4) magnetosomes but, compared to those made of magnetite, relatively little is known about the sedimentary environments where they are produced and the magnetic properties of the preserved particles. We studied the magnetic properties of sediment cores from two basins (the North Central Baltic Proper and eastern Gotland Basin) that currently experience hypoxia and we discovered the magnetic enhancement of older laminated sapropels, which are a signal of past occurrences of anoxia and hypoxia in the Baltic Sea. Magnetic concentrates extracted from the laminated sapropels were characterised by transmission electron microscopy and energy dispersive X-ray spectrometry and we identified only single-domain greigite (Fe3S4) particles with a mean size of 55×75nm, which we interpret as magnetofossils due to diagnostic chains of individual particles separated by an intact dividing membrane. The degree of magnetic enhancement in the laminated sapropels has a positive relationship with loss-on-ignition data, which indicates a link between the production of greigite magnetosomes, organic matter supply and preservation and redox conditions. The coercive force of collections of non-interacting greigite magnetofossils is ~13mT, which is considerably lower than the magnetite counterparts (~30mT) and strictly non-bacterial and larger greigite single-domain grains (~60mT). The values of the interparametric ratios of SIRM/χ, χARM/SIRM and χARM/χ that we obtain for our greigite magnetofossils overlap with those previously considered to be diagnostic of magnetosomal magnetite. The presence of bacterial greigite, which is easily detected by magnetic measurements, forms a proxy for hypoxia and anoxia, thus aiding the palaeoenvironmental interpretation of how oxygen conditions in the Baltic Sea have changed over time. © 2013 Elsevier B.V.
Malehmir A.,Uppsala University |
Saleem M.U.,Uppsala University |
Bastani M.,Geological Survey of Sweden
Journal of Applied Geophysics | Year: 2013
We present high-resolution reflection seismic data from four lines (total 1.9. km) that cross a quick-clay landslide scar located close to the shore of the Göta River in southwest Sweden, and compare the results with geotechnical data from boreholes. The seismic data allow the imaging of bedrock topography and normally to weakly consolidated sediments to a subsurface depth of about 100. m. Different types of seismic sources, including sledgehammer, accelerated weight-drop and dynamite were utilized and compared with each other. Analysis of their power spectra suggests that weight-drop and dynamite have higher frequency content and energy than the sledgehammer, which makes these two sources suitable also for waveform tomography and surface-wave data analysis. The shallowest non-bedrock reflector is observed at about 10-20. m below the surface, it overlays the bedrock, and is interpreted to originate from the contact between clay formations above and a coarse-grained layer below. The coarse-grained layer appears to be spatially linked to the presence of quick-clays. It is a regional scale formation, laterally heterogeneous, which deepens to the west of the study area and correlates well with the available geotechnical data. Continuity of the coarse-grained layer becomes obscured by the landslide scar. There may be a link between the coarse-grained layer and landslides in the study area, although this possibility requires further hydrogeological and geotechnical investigations. Reflectors from the top of the bedrock suggest a depression zone with its deepest point below the landslide scar and a bowl-shaped structure in the northern portion of one of the seismic lines. © 2013 Elsevier B.V.
Saintot A.,Geological Survey of Norway |
Stephens M.B.,Geological Survey of Sweden |
Viola G.,Geological Survey of Norway |
Nordgulen O.,Geological Survey of Norway
Tectonics | Year: 2011
Six hundred fault slip data have provided robust paleostress fields within an approximately 35 km3 volume of Paleoproterozoic (1.9 Ga) rocks in the southwestern Fennoscandian Shield, Forsmark, Sweden. These rocks were affected by penetrative ductile strain from 1.87 to 1.86 Ga, folding, ductile strain along discrete zones around 1.8 Ga, and semibrittle or brittle deformation around and after 1.8 Ga. Compatible paleostress fields have been identified using site-by-site and merged data sets from outcrops and oriented drill cores. Transpressive deformation with a regional NNW-SSE 1 axis, associated with clockwise stress deviation inside a tectonic lens, resulted in dextral slip along regionally significant, steep WNW-ESE and NW-SE deformation zones. The semibrittle and most of the brittle structures, including specifically the epidote-bearing fractures, were established during this oldest regime around 1.8 Ga (latest Svecokarelian). A younger paleostress field with a NE-SW 1 axis, which was also transpressive in character, is inferred to have been active at 1.7-1.6 Ga. The best defined paleostress field is transpressive in character with a WNW-ESE 1 axis that resulted in sinistral reactivation along the WNW-ESE and NW-SE zones. The main set of laumontite-stepped faults developed at this stage at 1.1-0.9 Ga (Sveconorwegian). It is impossible to exclude fully the influence of reactivation during even younger Phanerozoic tectonic events. Subordinate extensional paleostress fields were related either to the latest Svecokarelian and Sveconorwegian transpressive regimes, due to 1 and 2 stress permutations, or to regional extensional tectonic regimes during the Meso- or Neoproterozoic or later during the Permo-Carboniferous and/or Mesozoic. Copyright 2011 by the American Geophysical Union.
Moller C.,Lund University |
Andersson J.,Geological Survey of Sweden |
Dyck B.,Lund University |
Antal Lundin I.,Geological Survey of Sweden
Lithos | Year: 2015
We demonstrate a case of eclogite exhumation in a partially molten, low-viscosity fold nappe within high-grade metamorphosed crust in the Eastern Segment of the Sveconorwegian orogen. The nappe formed during tectonic extrusion, melt-weakening assisted exhumation and foreland-directed translation of eclogitized crust, and stalled at 35-40. km depth within the collisional belt. The eclogites are structurally restricted to a regional recumbent fold in which stromatic orthogneiss with pods of amphibolitized eclogite make up the core. High-temperature mylonitic gneiss with remnants of kyanite eclogite (P. >. 15. kbar) composes a basal shear zone 50. km long and <. 4. km wide. Heterogeneously sheared and partly migmatized augen gneiss forms a tectonostratigraphic marker in front of and beneath the nappe, and is in turn structurally enveloped by a composite sequence of orthogneisses and metabasites. The entire tectonostratigraphic pile underwent near-pervasive deformation and recrystallization under high-pressure granulite and upper amphibolite conditions. U-Pb SIMS metamorphic zircon ages of eclogite and stromatic orthogneiss constrain the time of eclogitization at 988. ± 6. Ma and 978. ± 7. Ma. Migmatization, concomitant deformation, and exhumation are dated at 976. ± 6. Ma, and crystallization of post-kinematic melt at 956. ± 7. Ma. Orthogneiss protoliths are dated at 1733. ± 11 and 1677. ± 10. Ma (stromatic gneiss) and 1388. ± 7. Ma (augen gneiss in footwall), demonstrating origins indigenous to the Eastern Segment. Eclogitization and exhumation were coeval with the Rigolet phase of the Grenvillian orogeny, reflecting the late stage of continental collision during construction of the supercontinent Rodinia. © 2015.
Zillen L.,Geological Survey of Sweden |
Lenz C.,Lund University |
Jilbert T.,University Utrecht
Quaternary Geochronology | Year: 2012
The prehistory of the Baltic Sea has for a long time suffered from imprecise dating, due to the large uncertainties associated with bulk radiocarbon dating of Baltic Sea sediments. To constrain the timing of environmental changes in the Baltic Sea it is critical to apply new dating approaches. This study identifies lead pollution isochrones in Baltic Sea sediments, which have previously been recorded in lake sediment and peat deposits in northern Europe and ice cores from Greenland. These isochrones have formed through the deposition of atmospheric lead associated with historic lead production and silver mining in Europe, and more recently with the increased industrial emissions that peaked in the 1970's. Lead concentration and stable lead isotope analyses ( 206Pb/ 207Pb ratios) reveal three distinct lead pollution horizons in the Baltic Sea, i.e. a Roman peak at 1 AD, a Medieval peak at 1200 AD and a peak in the 1970s. The new data will improve the chronological accuracy and precision of paleoenvironmental studies in the Baltic Sea, and for the first time, allow synchronization of Baltic Sea geological records within the basin and across Europe and the North Atlantic region (including Greenland). © 2011 Elsevier B.V.
Ulmius J.,Lund University |
Andersson J.,Geological Survey of Sweden |
Moller C.,Lund University
Precambrian Research | Year: 2015
The southernmost Baltic Shield exposes polymetamorphic continental crust that was largely formed and accreted during a series of 1.92-1.66. Ga Paleoproterozoic orogenic events and later reworked during the 1.14-0.90. Ga Sveconorwegian orogeny. An intermediate period of metamorphism, deformation and magmatism at 1.47-1.38. Ga has been attributed to the Hallandian orogeny, but due to overprinting by Sveconorwegian high-grade metamorphism and deformation, the P-T-t evolution and deformation of the Hallandian event have remained obscure. This study presents the first quantitative P-T model of the Hallandian event using high-temperature aluminous gneisses in the south-easternmost marginal part of the Sveconorwegian orogen. The high-grade metamorphism and spatially associated granite magmatism are dated using U-Pb SIMS analysis of zircon. Petrography, bulk and mineral geochemistry, and pseudosection models demonstrate prograde staurolite-sillimanite-grade metamorphism reaching granulite-facies temperatures (700-750. °C) at low pressures (4-5. kbar), with the formation of Crd. +. Sil. +. Grt. +. K-fsp. +. Ilm. +. Melt. ±. Bt. The rocks followed a clockwise P-T path. Later stages involved the formation of sillimanite. +. biotite at the expense of garnet and cordierite. Local low-temperature and fluid-assisted retrogression also caused the formation of chlorite and muscovite at the expense of cordierite. Both granite and aluminous gneisses contain complex zircon with inherited 1.70. Ga igneous cores and high-U, secondary zircon, mainly formed by reworking of protolith cores. The latter date the Hallandian high-grade metamorphism at 1451. ±. 6. Ma and the granite magmatism at 1445. ±. 8. Ma. The presence of 1.70. Ga igneous zircon cores in both metamorphic and magmatic rocks suggests that they formed from similar protoliths. The protolith ages correlate with the youngest generation of magmatic rocks of the Transscandinavian Igneous Belt. The aluminous gneisses are of supracrustal origin, and may have formed by chemical alteration of magmatic rocks. Hallandian regional metamorphism took place under a strongly elevated geotherm and was associated with granitic magmatism, suggesting an accretionary orogenic setting. The Hallandian event may demonstrate an 1.47-1.38. Ga Andean-type continental margin at the SW margin of Baltica. © 2015 Elsevier B.V..
Sadeghi M.,Geological Survey of Sweden |
Billay A.,Council for Geoscience |
Carranza E.J.M.,James Cook University
Journal of Geochemical Exploration | Year: 2015
Previous exploration activities in the Giyani greenstone belt (GGB) were guided by the availability of outcrops, particularly iron formation, as this rock was considered to be the main host rock for gold mineralisation in the belt, although the majority of the known prospects/deposits are hosted by mafic rocks. However, there is no reliable lithological map available for the GGB, because most of it is covered by regolith, and thus in the early 1990s most mining and exploration companies in the GGB have abandoned their work as they were discouraged by the scarcity of outcrops, the small sizes of existing deposits and the low gold prices at that time. In the present study, major and trace element geochemical data from a high-density soil geochemical survey (1 sample/km2) have been subjected to statistical and spatial analyses to support bedrock mapping and gold exploration. Maps are presented for major oxides, trace elements and selected respective ratio maps, and principal components (PC). The PC analysis was performed on clr-transformed data of selected trace elements known to be associated with gold mineralisation. The first six PCs explain about 78% of the total variance. PC4 representing Sb-As-Te-Cr-Au association best reflects the known gold mineralisation and was, therefore, used as a thematic layer. The information provided by various composite maps of different major/trace element data, as well as PC maps, has been used to produce an interpretive bedrock map outlining major lithological units in the study area. As gold mineralisation in the Giyani greenstone belt is hosted by certain known lithologies, the map is useful in indicating potential gold bearing areas. © 2014 Elsevier B.V.
Carranza E.J.M.,University of Twente |
Sadeghi M.,Geological Survey of Sweden
Ore Geology Reviews | Year: 2010
Mapping of mineral prospectivity and assessment of undiscovered mineral deposits both aim to delineate prospective ground for mineral exploration, but the latter is usually carried out exclusive of the former. We propose that the spatial distribution of known mineral deposits of the type sought is the key to link mapping of mineral prospectivity and assessment of undiscovered deposits. We demonstrate this proposition in regional-scale mapping of prospectivity for volcanogenic massive sulphides (VMS) deposits and estimation of undiscovered VMS endowment in the Skellefte district (Sweden). The results of analyses of the spatial distribution of known VMS deposits and their spatial associations with geological features are consistent with existing knowledge of geological controls on VMS mineralization in the district, and we used them to define spatial recognition criteria of regional-scale VMS prospectivity. Integration of layers of evidence representing spatial recognition criteria of VMS prospectivity via application of data-driven evidential belief functions results in a regional-scale map of prospective areas occupying 15% of the district and having fitting- and prediction-rates of 100%. We used the map of prospective areas and proxy measures for degrees of exploration based on the spatial distribution of known VMS deposits in one-level prediction of undiscovered mineral endowment. We obtained estimates of 709. Kt undiscovered Cu endowment, 3190. Kt undiscovered Zn endowment, 95. Mt undiscovered ore tonnage, and 48 undiscovered VMS deposits. These estimates are slightly (ca. 5% on average) lower than, and thus corroborated by, estimates obtained via radial-density fractal analysis of the spatial distribution of known VMS deposits. Therefore, mineral prospectivity mapping can be a part of mineral resource assessment if the spatial distribution of discovered deposits of the type sought is considered in both predictive modeling processes. © 2010 Elsevier B.V.