Chronology and processes of late Quaternary hillslope sedimentation in the eastern South Island,New Zealand          下载免费PDF全文

Josh Borella  Mark Quigley  Reza Sohbati  Peter Almond  Darren M. Gravley  Andrew Murray 《第四纪科学杂志》2016,31(7):691-712

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Three decades of water quality measurements from the Upper Severn experimental catchments at Plynlimon,Wales: an openly accessible data resource for research,modelling, environmental management and education   总被引：1，自引：0，他引：1  

Colin Neal  Brian Reynolds  Dave Norris  James W. Kirchner  Margaret Neal  Phil Rowland  Heather Wickham  Sarah Harman  Linda Armstrong  Darren Sleep  Alan Lawlor  Clive Woods  Bronwen Williams  Matt Fry  Gwen Newton  Dan Wright 《水文研究》2011,25(24):3818-3830

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Effects of projected climate change on the hydrology in the Mono Lake Basin, California   总被引：2，自引：0，他引：2  

Darren L. Ficklin  Iris T. Stewart  Edwin P. Maurer 《Climatic change》2013,116(1):111-131

The Californian Mono Lake Basin (MLB) is a fragile ecosystem, for which a 1983 ruling carefully balanced water diversions with ecological needs without the consideration of global climate change. The hydroclimatologic response to the impact of projected climatic changes in the MLB has not been comprehensively assessed and is the focus of this study. Downscaled temperature and precipitation projections from 16 Global Climate Models (GCMs), using two emission scenarios (B1 and A2), were used to drive a calibrated Soil and Water Assessment Tool (SWAT) hydrologic model to assess the effects on streamflow on the two significant inflows to the MLB, Lee Vining and Rush Creeks. For the MLB, the GCM ensemble output suggests significant increases in annual temperature, averaging 2.5 and 4.1 °C for the B1 and A2 emission scenarios, respectively, with concurrent small (1–3 %) decreases in annual precipitation by the end of the century. Annual total evapotranspiration is projected to increase by 10 mm by the end of the century for both emission scenarios. SWAT modeling results suggest a significant hydrologic response in the MLB by the end of the century that includes a) decreases in annual streamflow by 15 % compared to historical conditions b) an advance of the peak snowmelt runoff to 1 month earlier (June to May), c) a decreased (10–15 %) occurrence of ‘wet’ hydrologic years, and d) and more frequent (7–22 %) drought conditions. Ecosystem health and water diversions may be affected by reduced water availability in the MLB by the end of the century.  相似文献   

Fossils Explained 48: Placodonts     

Darren Naish 《Geology Today》2004,20(4):153-158

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The 2dF Galaxy Redshift Survey: galaxy luminosity functions per spectral type     

Darren S. Madgwick  Ofer Lahav  Ivan K. Baldry  Carlton M. Baugh  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Matthew Colless  Chris Collins  Warrick Couch  Gavin Dalton  Roberto De Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Carole Jackson  Ian Lewis  Stuart Lumsden  Steve Maddox  Peder Norberg  John A. Peacock  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,333(1):133-144

We calculate the optical b _J luminosity function (LF) of the 2dF Galaxy Redshift Survey (2dFGRS) for different subsets defined by their spectral properties. These spectrally selected subsets are defined using a new parameter, η , which is a linear combination of the first two projections derived from a Principal Component Analysis. This parameter η identifies the average emission- and absorption-line strength in the galaxy rest frame spectrum, and hence is a useful indicator of the present star formation. We use a total of 75 000 galaxies in our calculations, chosen from a sample of high signal-to-noise ratio, low-redshift galaxies observed before 2001 January. We find that there is a systematic steepening of the faint-end slope ( α ) as one moves from passive  ( α =-0.54)  to active  ( α =-1.50)  star-forming galaxies, and that there is also a corresponding faintening of the rest frame characteristic magnitude   M *-5 log₁₀( h )  (from −19.6 to −19.2). We also show that the Schechter function provides a poor fit to the quiescent (Type 1) LF for very faint galaxies  [ M _{b J}-5 log₁₀( h )  fainter than −16.0], perhaps suggesting the presence of a significant dwarf population. The LFs presented here give a precise confirmation of the trends seen previously in a much smaller preliminary 2dFGRS sample, and in other surveys. We also present a new procedure for determining self-consistent k -corrections, and investigate possible fibre-aperture biases.  相似文献   

The 2dF Galaxy Redshift Survey: the dependence of galaxy clustering on luminosity and spectral type   总被引：1，自引：0，他引：1  

Peder Norberg  Carlton M. Baugh  Ed Hawkins  Steve Maddox  Darren Madgwick  Ofer Lahav  Shaun Cole  Carlos S. Frenk  Ivan Baldry  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Matthew Colless  Chris Collins  Warrick Couch  Gavin Dalton  Roberto De Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Karl Glazebrook  Carole Jackson  Ian Lewis  Stuart Lumsden  John A. Peacock  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,332(4):827-838

We investigate the dependence of galaxy clustering on luminosity and spectral type using the 2dF Galaxy Redshift Survey (2dFGRS). Spectral types are assigned using the principal-component analysis of Madgwick et al. We divide the sample into two broad spectral classes: galaxies with strong emission lines ('late types') and more quiescent galaxies ('early types'). We measure the clustering in real space, free from any distortion of the clustering pattern owing to peculiar velocities, for a series of volume-limited samples. The projected correlation functions of both spectral types are well described by a power law for transverse separations in the range  2<( σ / h ^-1 Mpc)<15  , with a marginally steeper slope for early types than late types. Both early and late types have approximately the same dependence of clustering strength on luminosity, with the clustering amplitude increasing by a factor of ∼2.5 between L * and 4 L *. At all luminosities, however, the correlation function amplitude for the early types is ∼50 per cent higher than that of the late types. These results support the view that luminosity, and not type, is the dominant factor in determining how the clustering strength of the whole galaxy population varies with luminosity.  相似文献   

The 2dF Galaxy Redshift Survey: the blue galaxy fraction and implications for the Butcher–Oemler effect     

Roberto De Propris  Matthew Colless  John A. Peacock  Warrick J. Couch  Simon P. Driver  Michael L. Balogh  Ivan K. Baldry  Carlton M. Baugh  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Chris Collins  Nicholas Cross  Gavin Dalton  George Efstathiou  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Edward Hawkins  Carole Jackson  Ofer Lahav  Ian Lewis  Stuart Lumsden  Steve Maddox  Darren Madgwick  Peder Norberg  Will Percival  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2004,351(1):125-132

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The wider context of the Lower Jurassic Toarcian oceanic anoxic event in Yorkshire coastal outcrops,UK     

Nicolas Thibault  Micha Ruhl  Clemens V. Ullmann  Christoph Korte  David B. Kemp  Darren R. Gröcke  Stephen P. Hesselbo 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(3):372-391

The Toarcian Oceanic Anoxic Event (T-OAE, ～183 Ma) was characterized by enhanced carbon burial, a prominent negative carbon-isotope excursion (CIE) in marine carbonate and organic matter, and numerous geochemical anomalies. A precursor excursion has also been documented at the Pliensbachian/Toarcian boundary, but its possible causes are less constrained. The T-OAE is intensively studied in the Cleveland Basin, Yorkshire, UK, whose sedimentary deposits have been litho-, bio- and chemostratigraphically characterised. Here, we present new elemental data produced by hand-held X-ray fluorescence analysis to test the expression of redox-sensitive trace metals and detrital elements across the upper Pliensbachian to mid-Toarcian of the Cleveland Basin. Detrital elemental concentrations (Al, Si, Ti, Zr) are used as proxies for siliciclastic grain content and thus, sea-level change, which match previous sequence stratigraphic interpretations from the Cleveland Basin. The timescale of the event is debated, though our new elemental proxies of relative sea level change show evidence for a cyclicity of 350 cm that may be indicative of ～405 kyr eccentricity cycles in Yorkshire. Trends in total organic carbon and redox-sensitive elements (S, Fe, Mo, As) confirm scenarios of widespread ocean deoxygenation across the T-OAE. The correlation of comparable trends in Mo across the T-OAE in Yorkshire and the Paris Basin suggests a similar oceanic drawdown of this element accompanying widespread anoxia in the two basins. Data from Yorkshire point to a transgressive trend at the time of the Mo drawdown, which contradicts the “basin restriction” model for the euxinic conditions that characterise the CIE interval.  相似文献   

Scaling and multivariate analysis of medium to large landslide events: Haida Gwaii, British Columbia     

Les Jagielko  Yvonne Elizabeth Martin  Darren Boyd Sjogren 《Natural Hazards》2012,60(2):321-344

Gimbarzevsky (1988) collected an exceptional landsliding inventory for Haida Gwaii, British Columbia that included over 8,000 landsliding vectors covering an area of approximately 10,000 km². This database was never published in the referred literature, despite its regional significance. It was collected prior to widespread application of GIS technologies in landsliding studies, limiting the analyses undertaken at the time. Gimbarzevsky identified landslides using 1:50,000 aerial photographs, and transferred the information to NTS map sheets. In our study, we digitized the landslide vectors from these original map sheets and connected each landslide to a digital elevation model. Lengths of landslide vectors are compared to the landsliding inventory for Haida Gwaii analyzed in Rood (1984), Martin Y et al. BC Can J Earth Sci 39:289–305 (2002); the latter inventory is based on larger-scale aerial photographs (~1:12,000). Rood’s database contains a more complete record of smaller landslides, while the inventory of Gimbarzevsky provides improved statistical representation of less frequent, medium to large landslides. It is suggested that combined landslide delineation at different scales could provide a more complete landslide record. Discriminant analysis was undertaken to assess which of nine predictor variables, chosen on the basis of mechanical theory, best predict failed versus unfailed locations. Seven of the nine variables were found to be statistically significant in discriminating amongst failed and unfailed locations. Results show that 81.7% of original grouped cases were correctly classified.  相似文献   

Impact of climate change on streamflow in the arid Shiyang River Basin of northwest China   总被引：2，自引：0，他引：2  

Zhonggen Wang  Darren L. Ficklin  Yongyong Zhang  Minghua Zhang 《水文研究》2012,26(18):2733-2744

Climate change may significantly affect the hydrological cycle and water resource management, especially in arid and semi‐arid regions. In this paper, output from the Providing Regional Climates for Impacts Studies (PRECIS) regional climate model were used in conjunction with the Soil and Water Assessment Tool (SWAT) to analyse the effects of climate change on streamflow of the Xiying and Zamu rivers in the Shiyang River basin, an important arid region in northwest China. After SWAT model calibration and validation, streamflow in the Shiyang River Basin was simulated using the PRECIS climate model data for greenhouse gas emission scenarios A2 (high emission rate) and B2 (low emission rate) developed by Intergovernmental Panel on Climate Change. Monthly streamflow and hydrological extremes were compared for present‐day years (1961–1990), the 2020s (2011–2040), 2050s (2041–2070) and 2080s (2071–2100). The results show that mean monthly streamflow in Shiyang River Basin generally increased in the 2020s, 2050s and 2080s between 0.7–6.1% at the Zamu gauging station and 0.1–4.8% at the Xiying gauging station. The monthly minimum streamflow increased persistently, but the maximum monthly streamflows increased in the 2020s and slightly decreased in the 2050s and 2080s. This study provides valuable information for guiding future water resource management in the Shiyang River Basin and other arid and semi‐arid regions in China. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献