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471.
D. Heath Jones Mike A. Read Will Saunders Matthew Colless Tom Jarrett Quentin A. Parker Anthony P. Fairall † Thomas Mauch Elaine M. Sadler Fred G. Watson Donna Burton Lachlan A. Campbell Paul Cass Scott M. Croom John Dawe † Kristin Fiegert Leela Frankcombe Malcolm Hartley John Huchra Dionne James Emma Kirby Ofer Lahav John Lucey Gary A. Mamon Lesa Moore Bruce A. Peterson Sayuri Prior Dominique Proust Ken Russell Vicky Safouris Ken-ichi Wakamatsu Eduard Westra Mary Williams 《Monthly notices of the Royal Astronomical Society》2009,399(2):683-698
We report the final redshift release of the 6dF Galaxy Survey (6dFGS), a combined redshift and peculiar velocity survey over the southern sky (| b | > 10°) . Its 136 304 spectra have yielded 110 256 new extragalactic redshifts and a new catalogue of 125 071 galaxies making near-complete samples with ( K , H , J , r F , b J ) ≤ (12.65, 12.95, 13.75, 15.60, 16.75) . The median redshift of the survey is 0.053. Survey data, including images, spectra, photometry and redshifts, are available through an online data base. We describe changes to the information in the data base since earlier interim data releases. Future releases will include velocity dispersions, distances and peculiar velocities for the brightest early-type galaxies, comprising about 10 per cent of the sample. Here we provide redshift maps of the southern local Universe with z ≤ 0.1 , showing nearby large-scale structures in hitherto unseen detail. A number of regions known previously to have a paucity of galaxies are confirmed as significantly underdense regions. The URL of the 6dFGS data base is http://www-wfau.roe.ac.uk/6dFGS . 相似文献
472.
Peter J. Crosdale Anatoly P. Sorokin Ken J. Woolfe David I. M. Macdonald 《International Journal of Coal Geology》2002,51(4)
Selected Tertiary coals from the Zeya–Buryea Basin, Far Eastern Russia, were investigated for aspects of their coal type, rank, depositional environment and post-depositional history. The coals have been examined in outcrop (lithotype logging), microscopically (maceral, reflectance and fluorescence), and geochemically (proximate analysis).Two laterally extensive coal-bearing horizons occur: one of Palaeocene age and the other of early Miocene age. The Palaeocene coals were investigated in active open-cut mines at Raichikhinsk and Yerkovtsi and the early Miocene deposit in an abandoned open-cut mine at Cergeyevka.Palaeocene coals at Raichikhinsk and Yerkovtsi were indistinguishable from each other macroscopically, microscopically, and geochemically. The deposits were sufficiently coalified that brightness logging could be undertaken. Dull coals, with numerous fusainous wisps, were dominant. Four dulling-up sequences, which represent stacked peat deposits, were observed at Raichikhinsk. At Yerkovtsi, only a small section of the middle of the seam, which was mostly dull and muddy coal, was investigated. Petrographically, these coals were dominated by inertinite group macerals, which is unusual in non-Gondwanan coals and rare in the Tertiary. Rank classification was problematic with volatile matter (VM) content of vitrain (daf), macroscopic appearance, and microscopic textures suggesting subbituminous B rank, but carbon content, moisture content and specific energy indicating a lignite rank.Notwithstanding complications of rank, estimates of the maximum-range burial depths were calculated. Taking the VM (daf) content of vitrain as 48%, burial depth estimates range from 900 m for a high geothermal gradient and long heating time to a maximum of 3300 m for a low geothermal gradient and short heating time. These estimates are maxima as the coal rank may be lower than implied by the VM.The Cergeyevka deposit is a soft brown coal. Limited sampling of the upper-most portion indicated a high moisture content (75% daf) and an unusual, hydrogen-rich geochemistry. Lack of identifiable liptinites using either reflected light or fluorescence microscopy suggested a significant bituminite component. Otherwise, the coals appear to be typical for the Tertiary. An estimate of 125 m maximum burial depth was obtained using the bed-moisture content of the coal, which is around the present burial depth.Comparison of present-day thicknesses with inferred burial depths suggests that at least 500 m of section is missing between the Palaeocene coals and the early Miocene coals.Palaeoenvironmental considerations suggest that fire played a significant role in the accumulation of the peats at Raichikhinsk and Yerkovtsi. At Cergeyevka, peat accumulation ended by drowning of the mire.Two tuff beds were recognised within the seam at Raichikhinsk and one in the seam at Yerkovtsi. Correlation of the tuff beds is uncertain but they should prove useful in regional coal seam correlation and interpreting coal depositional environments. Geochemical analysis by XRF was complicated by high loss-on-ignition (LOI) values. Despite extensive alteration, an acid igneous source is implied from the presence of free quartz and TiO2/Al2O3 ratios of 0.02 to 0.05. 相似文献
473.
Bernadette Quémerais Ken R. Lum Claire Lemieux 《Aquatic Sciences - Research Across Boundaries》1996,58(1):52-68
Samples of raw water were collected in the St. Lawrence River during six sampling trips from August 1990 to April 1992. Water samples were analyzed for both dissolved and particulate phases for five trace metals. Partition coefficients (Kd) and metal fluxes were calculated in order to determine metal transport. A mass balance equation was used for the determination of the major metal sources to the St. Lawrence River and an estimation of metal loadings to the estuary was made. Average dissolved metal concentrations were found to be Cd 10 ng/L, Co 74 ng/L, Cu 64 ng/L, Fe 69 µg/L and Mn 700 ng/L. Particulate concentrations were (in µg/g) 1.68 for Cd, 31 for Co, 73 for Cu, 25 mg/g for Fe and 1.69 mg/g for Mn. Co, Fe and Mn were transported essentially in the particulate phase while Cd and Cu were predominantly found in the dissolved phase at 56% and 48% of the total metal concentration respectively. Log Kd values varied from 5.1 (for Cu) to 6.8 (for Mn). In the dissolved phase the major sources were found to be the Great Lakes and the Ottawa River whereas in the particulate phase Québec tributaries appear to be the most important. Industrial inputs are quite important in both the dissolved and the particulate phases for Cd, whereas other sources are very variable, especially for the dissolved phase. 相似文献
474.
Stephen P. Miller Ken C. Macdonald Peter F. Lonsdale 《Marine Geophysical Researches》1985,7(3):401-418
Results are presented from a high precision geophysical profile made at an altitude of about 100 m above the sea floor with the Deep Two instrument package, crossing the Red Sea at 17°30N. The emphasis is on the analysis and interpretation of the magnetic field, including an inversion which removes the distortions due to bathymetry and the orientation with respect to the earth's main field vector. The spreading rates are determined precisely and found to be highly asymmetric: only 5 mm yr-1 to the east and up to 10 mm yr-1 to the west. We conclude that the axis of spreading is located on a volcanic ridge, rather than on the axial graben, based on the presence of a zone of high magnetization. The magnetization high (40 Am-1) is about twice as great as found on the Mid-Atlantic Ridge with the same instrument and analysis. The quality of the recording of the magnetic anomalies in the oceanic crust is much greater than expected for such a low spreading rate. 相似文献
475.
476.
Laura Jean Perram Ken C. Macdonald Stephen P. Miller 《Marine Geophysical Researches》1990,12(3):235-245
Six Deep-Tow magnetic profiles across the axis of the East Pacific Rise [EPR] in two small areas between 19°25 and 20°10S were collected during the 1983 Protea 1 cruise of the R/V Melville. These near-bottom profiles are of extremely high resolution allowing the interpretation of very short wavelength features. We have inverted the magnetic field data to determine the rock magnetization distribution near the axis of this ultrafast speading center (162 mm yr-1). The solutions reveal large amplitude (up to 35 A m-1) short wavelength (1–3 km) variations in magnetization. Specifically all crossings show a narrow (0.5 to 1.5 km) low in magnetization superimposed on a broader (2.5 to 4 km) high directly over the ridge axis. Four profiles in the northern area (19°25 to 19°33S) also show symmetrical near-axis (within 4 km) lows which are remarkably continuous along strike. Explanations for the short-wavelength variations are discussed which fall into the following categories: (1) variations in the thickness of the magnetized layer, (2) variations in rock chemistry (e.g. alteration due to hydrothermal activity), and (3) paleofield intensity variations. None of the mechanisms discussed alone adequately explain the observed phenomena in the study area or on a world-wide scale. Further sampling and high resolution surveying will be required in order to accurately determine the relative importance of the mechanisms discussed. 相似文献
477.
John D. Bicknell Ken C. MacDonald Stephen P. Miller Peter F. Lonsdale Keir Becker 《Marine Geophysical Researches》1986,8(2):131-148
The Nereus Deep (23°N) lies in the central portion of the Red Sea, in a region which marks a transition between the nearly continuous axial rift valley of the southern Red Sea and the northern Red Sea, where a well defined axial rift is absent. The deep-tow survey and associated heat flow measurements reported here show that the Nereus Deep is a short segment of axial rift, and it is the northernmost deep where petrology, heat flow, magnetics, and morphology all indicate classic seafloor spreading. Heat flow measured in the Nereus Deep is characterized by non-linear gradients and closely-spaced variability indicative of active hydrothermal circulation associated with seafloor spreading. The two axial highs which we have mapped in Nereus differ markedly in that the southernmost appears younger or at least has had a more recent phase of volcanism. The two axial highs are offset left laterally approximately 2 km. This small offset or bend in the axial course has been labelled the Nereus shear zone, and, despite its small extent, it mimics many of the major features of small offset, slow-slipping transform faults. This shear zone may result from shear stresses associated with misalignments in succeeding volcanic episodes. The Nereus Deep appears to represent one of the earliest phases of seafloor spreading. The Red Sea seems to be opening towards the north, and the Nereus Deep is near the tip of propagation, but it is clear from this study that rift propagation in a site of initial rifting differs greatly from that observed along a well developed, fast spreading center like the East Pacific Rise. 相似文献
478.
Phytoplankton distribution in a frontal region of Tokyo Bay was investigated in relation to hydrography in November 1985. The frontal region was observed from the central to the mouth area of the bay and consisted of a series of fine scale discontinuities of salinity and temperature. Among them the Kenzaki offshore front (KOF) and the Yokosuka inshore front (YIF) were most prominent in terms of the duration and the magnitudes of the hydrographic gaps. Three major phytoplankton assemblages were observed: (A) neritic and offshore diatoms in the mouth area of Tokyo Bay, (B) a diatomLeptocylindrus danicus and dinoflagellates in the central area, and (C) bloom forming cryptophyceans, dinoflagellates andL. danicus from the inner Tokyo Bay. The KOF was an approximate boundary of the outside assemblage (A) and the intermediate population (B), and the YIF was that of (B) and the inner bay population (C). Species changes across the fronts were rather gradual in the KOF making a strong contrast to distinct jumps in temperature, salinity,in vivo chlorophyll fluorescence and nitrate plus nitrite. An outward surface flow of the inside population along the western coast off Yokosuka was detected. 相似文献
479.
The tectonically active islands of the Indo-Pacific Archipelago deliver much sediment to the ocean margins. In the Gulf of Papua on the south coast of Papua New Guinea (PNG), the chemical composition of surface sediment from grab samples indicates that Fly River muds are dispersed to the north and east, where they are joined by sediment plumes from the other large rivers along the south coast of PNG. This is the likely source of terrestrial sediment on the Papuan Plateau and the northern Coral Sea Abyssal Plain. The sediment is transported through submarine troughs and canyons offshore, far to the east of the riverine inputs. Immediately south and 30–50 km offshore from the Fly and Purari deltas is a platform of algal and reef carbonate materials, containing little or no terrestrial surface sediment. 相似文献
480.
Michiel Rutgers van der Loeff Manmohan M. Sarin Mark Baskaran Claudia Benitez-Nelson Ken O. Buesseler Matt Charette Minhan Dai
rjan Gustafsson Pere Masque Paul J. Morris Kent Orlandini Alessia Rodriguez y Baena Nicolas Savoye Sabine Schmidt Robert Turnewitsch Ingrid Vge James T. Waples 《Marine Chemistry》2006,100(3-4):190
The short-lived thorium isotope 234Th (half-life 24.1 days) has been used as a tracer for a variety of transport processes in aquatic systems. Its use as a tracer of oceanic export via sinking particles has stimulated a rapidly increasing number of studies that require analyses of 234Th in both marine and freshwater systems. The original 234Th method is labor intensive. Thus, there has been a quest for simpler techniques that require smaller sample volumes. Here, we review current methodologies in the collection and analysis of 234Th from the water column, discuss their individual strengths and weaknesses, and provide an outlook on possible further improvements and future challenges. Also included in this review are recommendations on calibration procedures and the production of standard reference materials as well as a flow chart designed to help researchers find the most appropriate 234Th analytical technique for a specific aquatic regime and known sampling constraints. 相似文献