Age and composition of dykes emplaced before and during the opening of the Tasman Sea—source implications     

R. Offler  H. Zwingmann  J. Foden  F. L. Sutherland  I. T. Graham 《Australian Journal of Earth Sciences》2013,60(8):1129-1144

Abstract

Dykes are common in the wave-cut platforms along the coast from Newcastle to Sydney. According to some authors, they may be related to the opening of the Tasman Sea that commenced ca 84?Ma ago. However, there are few detailed radiogenic dating and geochemical studies to evaluate this. We attempt to resolve this by K–Ar dating of plagioclase in and geochemical studies of, basaltic dykes intruding Permo-Triassic sequences on the wave-cut platforms and Carboniferous and Permo-Triassic sequences inland. The plagioclase separated from the dykes give K–Ar ages ranging from 266 to 53?Ma with the majority older than 84?Ma indicating that most dykes were emplaced before the Tasman Seafloor formation. The dykes are generally mildly alkaline, high-Ti basalts; fewer are tholeiitic and calc-alkaline, low-Ti basalts. Strongly light rare earth element (LREE)-enriched patterns typify the former and flat, LREE-depleted or slightly to moderately enriched LREE patterns, the latter. High-Ti basalts have ocean-island-basalt-like and low-Ti basalts, calc-alkaline or mid-ocean ridge basalt (MORB)-like patterns. Most high-Ti and some low-Ti basalts show plume-like characteristics, others N-type MORB and arc-like characteristics. Dykes intruding the Carboniferous sequences show a distinct contamination signature that could be crustal or due to subduction-related metasomatism of the subcontinental lithospheric mantle. The sources of the basaltic magmas vary substantially and in places changes with time. All alkali basalts are derived from enriched asthenospheric sources at varying depths (90–147?km) and most tholeiitic, low-Ti basalts have been extracted from asthenospheric and depleted asthenospheric–lithospheric sources indicating substantial compositional heterogeneity of the mantle. Further, Nd model ages varying from Neoproterozoic (940–580?Ma) to Paleozoic (460–370?Ma) suggest variation in the age of mantle sources for the basalts.  相似文献   

VARIABILITY OF IN-CHANNEL SEDIMENT STORAGE WITHIN A SMALL SEMIARID DRAINAGE BASIN     

Ross A. Sutherland 《自然地理学》2013,34(1):75-93

This study determines the spatial and temporal variability of in-channel storage within a small semiarid drainage basin in equatorial East Africa, and establishes a tentative sediment budget for coarse (>200 μm) in-channel sediments. Detailed measurements of in-channel sediment storage (mass) within third and fourth-order ephemeral channels were obtained using channel-pit excavations and probing with metal rods. Eighty-seven monumented cross-sections were established in February 1986 and resurveyed in December 1986, following the last runoff event of the year. These provided data on change in sediment storage on a 30-m channel reach basis. In addition, measurements of bankfull channel width, mean depth, cross-sectional area, wetted perimeter, hydraulic radius, channel slope and distance from the basin outlet were measured at each cross section. Total in-channel sediment storage was approximately 8640 t with 83% of this total stored within the Main (fourth-order) Channel. Stepwise multiple regression of In-transformed data indicated that bankfull channel width and distance from the outlet (which is strongly related with slope) were significantly related to in-channel storage. The variation in the ratio of stream power:critical power along the Main Channel may explain the distribution of in-channel sediments. Net aggradation of 50 to 60 t during 1986 was minor in relation to the total in-channel storage reservoir, but indicates that a static equilibrium condition cannot be assumed. Bedload output during 1986 was approximately 125 t, and the computed input of coarse sediments to the major channels within the basin was approximately 185 t. The sediment delivery ratio for the coarse material was approximately 68%, which indicates a relatively efficient transport system. [Key words: geomorphology, sediment budget, in-channel sediment storage, semiarid, drainage basin.]  相似文献   

The 2dF Galaxy Redshift Survey: the bias of galaxies and the density of the Universe   总被引：1，自引：0，他引：1  

Licia Verde  Alan F. Heavens  Will J. Percival  Sabino Matarrese  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  Ofer Lahav  Ian Lewis  Stuart Lumsden  Steve Maddox  Darren Madgwick  Peder Norberg  John A. Peacock  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,335(2):432-440

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Interactions of jets with inhomogeneous cloudy media     

Curtis J. Saxton  Geoffrey V. Bicknell  Ralph S. Sutherland  Stuart Midgley 《Monthly notices of the Royal Astronomical Society》2005,359(2):781-800

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The 2dF Galaxy Redshift Survey: a targeted study of catalogued clusters of galaxies     

Roberto De Propris  Warrick J. Couch  Matthew Colless  Gavin B. Dalton  Chris Collins  Carlton M. Baugh  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Nicholas Cross  Kathryn Deeley  Simon P. Driver  George Efstathiou  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Carole Jackson  Ofer Lahav  Ian Lewis  Stuart Lumsden  Steve Maddox  Darren Madgwick  Stephen Moody  Peder Norberg  John A. Peacock  Will Percival  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,329(1):87-101

We have carried out a study of known clusters within the 2dF Galaxy Redshift Survey (2dFGRS) observed areas and have identified 431 Abell, 173 APM and 343 EDCC clusters. Precise redshifts, velocity dispersions and new centroids have been measured for the majority of these objects, and this information is used to study the completeness of these catalogues, the level of contamination from foreground and background structures along the cluster's line of sight, the space density of the clusters as a function of redshift, and their velocity dispersion distributions. We find that the Abell and EDCC catalogues are contaminated at the level of about 10 per cent, whereas the APM catalogue suffers only 5 per cent contamination. If we use the original catalogue centroids, the level of contamination rises to approximately 15 per cent for the Abell and EDCC catalogues, showing that the presence of foreground and background groups may alter the richness of clusters in these catalogues. There is a deficiency of clusters at     that may correspond to a large underdensity in the Southern hemisphere. From the cumulative distribution of velocity dispersions for these clusters, we derive a space density of     clusters of     This result is used to constrain models for structure formation; our data favour low-density cosmologies, subject to the usual assumptions concerning the shape and normalization of the power spectrum.  相似文献   

The 2dF Galaxy Redshift Survey: luminosity functions by density environment and galaxy type     

Darren J. Croton  Glennys R. Farrar  Peder Norberg  Matthew Colless  John A. Peacock  I. K. Baldry  C. M. Baugh  J. Bland-Hawthorn  T. Bridges  R. Cannon  S. Cole  C. Collins  W. Couch  G. Dalton  R. De Propris  S. P. Driver  G. Efstathiou  R. S. Ellis  C. S. Frenk  K. Glazebrook  C. Jackson  O. Lahav  I. Lewis  S. Lumsden  S. Maddox  D. Madgwick  B. A. Peterson  W. Sutherland  K. Taylor 《Monthly notices of the Royal Astronomical Society》2005,356(3):1155-1167

We use the 2dF Galaxy Redshift Survey to measure the dependence of the b _J-band galaxy luminosity function on large-scale environment, defined by density contrast in spheres of radius  8  h ⁻¹ Mpc  , and on spectral type, determined from principal component analysis. We find that the galaxy populations at both extremes of density differ significantly from that at the mean density. The population in voids is dominated by late types and shows, relative to the mean, a deficit of galaxies that becomes increasingly pronounced at magnitudes brighter than   M _{b J}−5log₁₀ h ≲−18.5  . In contrast, cluster regions have a relative excess of very bright early-type galaxies with   M _{b J}−5log₁₀ h ≲−21  . Differences in the mid- to faint-end population between environments are significant: at   M _{b J}−5log₁₀ h =−18  early- and late-type cluster galaxies show comparable abundances, whereas in voids the late types dominate by almost an order of magnitude. We find that the luminosity functions measured in all density environments, from voids to clusters, can be approximated by Schechter functions with parameters that vary smoothly with local density, but in a fashion that differs strikingly for early- and late-type galaxies. These observed variations, combined with our finding that the faint-end slope of the overall luminosity function depends at most weakly on density environment, may prove to be a significant challenge for models of galaxy formation.  相似文献   

The 2dF Galaxy Redshift Survey: correlation functions, peculiar velocities and the matter density of the Universe   总被引：1，自引：0，他引：1  

Ed Hawkins  Steve Maddox  Shaun Cole  Ofer Lahav  Darren S. Madgwick  Peder Norberg  John A. Peacock  Ivan K. Baldry  Carlton M. Baugh  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  Carlos S. Frenk  Karl Glazebrook  Carole Jackson  Bryn Jones  Ian Lewis  Stuart Lumsden  Will Percival  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2003,346(1):78-96

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The 2dF Galaxy Redshift Survey: stochastic relative biasing between galaxy populations     

Vivienne Wild  John A. Peacock  Ofer Lahav  Edward Conway  Steve Maddox  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  Darren Madgwick  Peder Norberg  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2005,356(1):247-269

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Tabbita: An L6c chondrite from New South Wales,Australia     

A. W. R. Bevan  B. Griffin  R. E. Pogson  F. L. Sutherland 《Meteoritics & planetary science》1992,27(1):97-98

Abstract— A crusted stone weighing 3.10 kg was found in 1983 near Tabbita in south central New South Wales (ca. 34°03′S, 145°50′E), Australia. Compositions of the ferro-magnesian silicates (olivine Fa_24.6; orthopyroxene Fs_20.9) show that the meteorite belongs to the L-group of chondrites. Uniformity of silicate compositions and the presence of abundant crystalline plagioclase feldspar (An_10.8Ab_81.7Or_7.5) show that the meteorite belongs to petrologic type 6. Silicates that display undulose extinction, and the absence of any thermal effects induced by shock indicate that Tabbita is shock facies c. Tabbita is distinct from several other L6 chondrites found in the same general area.  相似文献   

The Millennium Galaxy Catalogue: the photometric accuracy, completeness and contamination of the 2dFGRS and SDSS-EDR/DR1 data sets     

N. J. G. Cross  S. P. Driver  J. Liske  D. J. Lemon  J. A. Peacock  S. Cole  P. Norberg  W. J. Sutherland 《Monthly notices of the Royal Astronomical Society》2004,349(2):576-594

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