Spring temperature variability in northern Fennoscandia AD 1693–2011     

Neil J. Loader  Risto Jalkanen  Danny Mccarroll  Anders Moberg 《第四纪科学杂志》2011,26(6):566-570

A reconstruction of spring (April–May) temperature for northern Fennoscandia developed from the Tornionjoki (Tornio river) long cryophenological record of ice break‐up dates, back to AD 1693, is presented. The record is strongly climatically sensitive and explains 67% of the variance in the instrumental data over the last 150 years. The record exhibits a stepped decrease in the duration of the river's ice cover by 14 days, equivalent to an increase in April–May mean temperature of approximately 2.5°C over the last three centuries. The relationship between the date of ice break‐up, and accumulated daily mean temperatures (>0°C) is investigated. Uncertainty in the observation of ice break‐up is also considered in addition to the potential of this time series for regional climate model validation. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Physics‐based simulation of multiple interacting crack growth in brittle rocks driven by thermal cooling          下载免费PDF全文

Hai Huang  Paul Meakin  Anders Malthe‐Sorenssen 《国际地质力学数值与分析法杂志》2016,40(16):2163-2177

Crack growth in hot brittle rocks, driven by thermal cooling, was simulated using a coupled two‐dimensional discrete element and heat transport model that explicitly includes the random initiation and subsequent propagation of interacting cracks. The model clearly predicts that a quasi‐hierarchical array of subparallel cracks, oriented along the direction of the temperature gradient, is formed under small to moderately large thermally generated strain load conditions. The simulation results also demonstrate that, after an initial transient, thermal cracks propagate in a stable fashion with a velocity that scales with ~ t^{− 1/2}. However, under large thermal strain loads, a more complicated geometry composed of cracks that curve and coalesce develops during the later stages of crack growth. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Progressive formation of modern drumlins at Múlajökull,Iceland: stratigraphical and morphological evidence          下载免费PDF全文

Ívar Örn Benediktsson  Sverrir A. Jónsson  Anders Schomacker  Mark D. Johnson  Ólafur Ingólfsson  Lucas Zoet  Neal R. Iverson  Johann Stötter 《Boreas: An International Journal of Quaternary Research》2016,45(4):567-583

The drumlin field at Múlajökull, Iceland, is considered to be an active field in that partly and fully ice‐covered drumlins are being shaped by the current glacier regime. We test the hypothesis that the drumlins form by a combination of erosion and deposition during successive surge cycles. We mapped and measured 143 drumlins and studied their stratigraphy in four exposures. All exposures reveal several till units where the youngest till commonly truncates older tills on the drumlin flanks and proximal slope. Drumlins inside a 1992 moraine are relatively long and narrow whereas drumlins outside the moraine are wider and shorter. A conceptual model suggests that radial crevasses create spatial heterogeneity in normal stress on the bed so that deposition is favoured beneath crevasses and erosion in adjacent areas. Consequently, the crevasse pattern of the glacier controls the location of proto‐drumlins. A feedback mechanism leads to continued crevassing and increased sedimentation at the location of the proto‐drumlins. The drumlin relief and elongation ratio increases as the glacier erodes the sides and drapes a new till over the landform through successive surges. Our observations of this only known active drumlin field may have implications for the formation and morphological evolution of Pleistocene drumlin fields with similar composition, and our model may be tested on modern drumlins that may become exposed upon future ice retreat.  相似文献   

Recommendations on methods for the detection and control of biological pollution in marine coastal waters     

Olenin S  Elliott M  Bysveen I  Culverhouse PF  Daunys D  Dubelaar GB  Gollasch S  Goulletquer P  Jelmert A  Kantor Y  Mézeth KB  Minchin D  Occhipinti-Ambrogi A  Olenina I  Vandekerkhove J 《Marine pollution bulletin》2011,62(12):2598-2604

Adverse effects of invasive alien species (IAS), or biological pollution, is an increasing problem in marine coastal waters, which remains high on the environmental management agenda. All maritime countries need to assess the size of this problem and consider effective mechanisms to prevent introductions, and if necessary and where possible to monitor, contain, control or eradicate the introduced impacting organisms. Despite this, and in contrast to more enclosed water bodies, the openness of marine systems indicates that once species are in an area then eradication is usually impossible. Most institutions in countries are aware of the problem and have sufficient governance in place for management. However, there is still a general lack of commitment and concerted action plans are needed to address this problem. This paper provides recommendations resulting from an international workshop based upon a large amount of experience relating to the assessment and control of biopollution.  相似文献   

Ecology of twelve species of Thyasiridae (Mollusca: Bivalvia)     

Keuning R  Schander C  Kongsrud JA  Willassen E 《Marine pollution bulletin》2011,62(4):786-791

Benthic samples from coastal locations off Southwestern Norway were examined and the specimens of Thyasiridae were identified to species. A multivariate analysis based on 13 parameters was carried out and the environmental preferences of all thyasirid species present were determined. The potential of the Thyasiridae as indicators of organic enrichment was investigated by using direct canonical correspondence analyses to identify correlations between selected environmental parameters and the collected biological data. The presence of Thyasira sarsi together with a low biodiversity is a good indicator of organic enrichment. High thyasirid species diversity seems to indicate good environmental conditions, and single thyasirid species that lack symbiotic bacteria might also be useful as indicators of good environmental conditions.  相似文献   

PAH body burden and biomarker responses in mussels (Mytilus edulis) exposed to produced water from a North Sea oil field: laboratory and field assessments     

Sundt RC  Pampanin DM  Grung M  Baršienė J  Ruus A 《Marine pollution bulletin》2011,62(7):1498-1505

In order to study the impact of produced water (PW) from a North Sea oil field on blue mussels (Mytilus edulis), chemical and biological markers were selected. A laboratory exposure (0.125%, 0.25% and 0.5% of PW) and a field study (6 stations 0.2-2 km from a PW discharge point) were conducted. In the laboratory study, PAH bioaccumulation increased in mussel soft tissue even at the lowest exposure dose. Micronuclei frequency demonstrated a dose-response pattern, whereas lysosomal membrane stability showed tendency towards a dose-response pattern. The same markers were assessed in the field study, biomarker analyses were consistent with the contamination level, as evaluated by mussel polycyclic aromatic hydrocarbons body burden. Overall, obtained results confirmed the value of an ecotoxicological approach for a scientifically sound characterisation of biological effects induced by offshore oilfield operational discharges.  相似文献   

Influence of Bedding Dip on Glacial Erosional Landforms,Uinta Mountains,USA     

Marissa H. Kelly  Alison M. Anders  Sara Gran Mitchell 《Geografiska Annaler: Series A, Physical Geography》2014,96(2):147-159

We explore the relationships amongst bedding dip, basin aspect, and glacial landforms using field observations and GIS analyses of the northwestern Uinta Mountains of Utah. We examine basins on opposing sides of three ice divides in which quartzite beds of the Mount Watson Formation maintain a near constant dip. These areas provide contrasting relationships between ice flow and bedding dip directions while holding rock type and climate constant. We map the occurrence of three glacial erosional landforms: cliffs showing evidence of quarrying, scoured surfaces polished by abrasion, and overdeepenings. Cliffs and overdeepenings are more common in basins where bedding dips up‐basin, while scoured surfaces are more prevalent where bedding dips down‐basin. The significance of jointing in controlling glacial erosional forms is well established and we propose that bedding, as well as joints, dictates the geometry of quarried blocks and influences the spatial patterns of process dominance. Where bedding dips up‐basin, the geometry of pre‐existing weaknesses favours quarrying creating both cliffs and overdeepenings. In contrast, where bedding dips down‐basin, block geometry does not favour the creation of overdeepenings via quarrying and exposed bedding planes are subjected to glacial abrasion, producing scoured surfaces.  相似文献   

Epithermal Gold Mineralization in the Trenggalek District,East Java,Indonesia     

Ryohei Takahashi  Yuki Shingo  Akira Imai  Koichiro Watanabe  Agung Harijoko  I Wayan Warmada  Arifudin Idrus  Lucas Donny Setijadji  Phouvang Phoumephone  Anders Scherstén  Laurence Page 《Resource Geology》2014,64(2):149-166

Gold‐mineralized quartz veins at the Trenggalek district of the Southern Mountains Range in East Java, Indonesia, are hosted by Oligo‐Miocene volcaniclastic and volcanic rocks, and are distributed close to andesitic plugs in the northern prospects (Dalangturu, Suruh, Jati, Gregah, Jombok, Salak, and Kojan) and the southern prospects (Sentul and Buluroto). The plugs are subalkaline tholeiitic basaltic‐andesite to calc‐alkaline andesite in composition. ⁴⁰Ar–³⁹Ar dating of a quartz‐adularia vein at the Dalangturu prospect yielded an age of 16.29 ± 0.56 Ma (2σ), and a crystal tuff of a limestone‐pyroclastic rock sequence at the southwest of the Dalangturu prospect was determined as 15.6 ± 0.5 Ma (2σ). Statistic overlap of ages suggests that the gold mineralization in the northern prospects took place in a shallow marine to subaerial transitional environment. Hydrothermal alteration of the host rocks is characterized by the replacement of quartz, illite and adularia. Quartz veins in surface outcrops are up to 50 cm wide in the northern prospects and up to 3 m wide in the southern prospects, showing a banded or brecciated texture, and are composed of quartz, adularia, carbonates with pyrite, electrum, sphalerite, galena, and polybasite. Gold contents of quartz veins are positively correlated with Ag, Zn, Pb, and Cu contents in both the northern and southern prospects. The quartz veins at the Jati, Gregah, and Sentul prospects have relatively lower gold‐silver ratios (Ag/Au = 23.2) compared to those at the Kojan, Dalangturu, Salak, and Suruh prospects (Ag/Au = 66.8). The quartz veins at the Dalangturu prospect are relatively rich in base metal sulfides. Ag/(Au+Ag) ratios of electrum in the Dalangturu prospect range from 45.2 to 65.0 at%, and FeS contents of sphalerite range from 1.2 to 6.4 mol%. Fluid inclusion microthermometry indicates ore‐forming temperatures of 190–200°C and 220–230°C at the Sentul and Kojan prospects, respectively. Widely variable vapor/liquid ratio of fluid inclusions indicates that fluid boiling took place within the hydrothermal system at the Sentul prospect. Salinities of ore‐fluids range from 0 to 0.7 wt% (av. 0.4 wt% NaCl equiv.) and from 0.5 to 1.4 wt% (av. 0.9 wt%) for the Sentul and Kojan prospects, respectively. The boiling of hydrothermal fluid was one of the gold deposition mechanisms in the Sentul prospect.  相似文献   

Onshore climate change during the Late Triassic marine inundation of the Central European Basin     

Anders Ahlberg  Leif Arndorff  & Dorothy Guy-Ohlson 《地学学报》2002,14(4):241-248

Sedimentological, pedological and palynological evidence reveal radically increasing onshore humidity during the Rhaetian marine invasion of central Europe along the north-eastern margin of the Central European Basin (southern Sweden). Pre-Rhaetian aridity favoured the formation of Carnian redbeds with calcrete, which were succeeded by Norian hematite-cemented conglomerates, arkoses, arkosic wackestones, and smectititic mudstones deposited on braidplains and in lakes. Superimposed autochthonous coals and gleysols indicate the Rhaetian onset of year-round humidity. Chemically mature sandstones, kaolinitic mudstones and luvisols also formed at this time, influenced by a permanent vegetation cover which lowered soil pH and strongly intensified chemical weathering. The Rhaetian deposits accumulated in floodplain lakes repeatedly subjected to sediment infill, plant colonization and palaeosol development. The humidity shift resembles that contemporaneously recorded in the North Sea region.  相似文献   

Star cluster formation and evolution in nearby starburst galaxies – I. Systematic uncertainties     

R. de Grijs  U. Fritze-v. Alvensleben  P. Anders  J. S. Gallagher III    N. Bastian  V. A. Taylor  R. A. Windhorst 《Monthly notices of the Royal Astronomical Society》2003,342(1):259-273

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