New records of Ediacaran Acraman ejecta in drillholes from the Stuart Shelf and Officer Basin,South Australia     

Andrew C. Hill  Peter W. Haines  Kathleen Grey  Sebastian Willman 《Meteoritics & planetary science》2007,42(11):1883-1891

Abstract— New occurrences of the Acraman impact ejecta layer were recently discovered in two South Australian drillholes, SCYW‐79 1a (Stuart Shelf) and Munta 1 (Officer Basin) using lithostratigraphy, acritarch biostratigraphy, carbon isotope stratigraphy, and biomarker anomalies to predict the stratigraphic position. The ejecta layer is conspicuous because it consists of pink, sandsized, angular fragments of volcanic rock distributed along the bedding plane surface of green marine siltstone. In SCYW‐79 1a it forms a layer 5 mm thick; in Munta 1 the ejecta layer is thin and discontinuous because of its distance (?550 km) from the impact structure. Palynological, biomarker, and carbon isotope anomalies can now be shown to coincide with the ejecta layer in SCYW‐79 1a and Munta 1 suggesting the Acraman impact event may have had far reaching influences on the rapidly evolving Ediacaran biological and geochemical cycles.  相似文献   

Metrics for the comparative analysis of geospatial datasets with applications to high-resolution grid-based population data     

Aarthy Sabesan  Kathleen Abercrombie  Auroop R. Ganguly  Budhendra Bhaduri  Eddie A. Bright  Phillip R. Coleman 《GeoJournal》2007,69(1-2):81-91

Geospatial data sciences have emerged as critical requirements for high-priority application solutions in diverse areas, including, but not limited to, the mitigation of natural and man-made disasters. Three sets of metrics, adopted or customized from geo-statistics, applied meteorology and signal processing, are tested in terms of their ability to evaluate geospatial datasets, specifically two population databases commonly used for disaster preparedness and consequence management. The two high-resolution, grid-based population datasets are the following: The LandScan dataset available from the Geographic Information Science and Technology (GIST) group at the Oak Ridge National Laboratory (ORNL), and the Gridded Population of the World (GPW) dataset available from the Center for International Earth Science Information Network (CIESIN) group at Columbia University. Case studies evaluate population data across the globe, specifically, the metropolitan areas of Washington DC, USA, Los-Angeles, USA, and Houston, USA, and London, UK, as well as the country of Iran. The geospatial metrics confirm that the two population datasets have significant differences, especially in the context of their utility for disaster readiness and mitigation. While this paper primarily focuses on grid based population datasets and disaster management applications, the sets of metrics developed here can be generalized to other geospatial datasets and applications. Future research needs to develop metrics for geospatial and temporal risks and associated uncertainties in the context of disaster management. The U. S. Government’s right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.  相似文献   

Aspects of Proterozoic stromatolite biostratigraphy in Western Australia     

Kathleen Grey 《Precambrian Research》1982,18(4):347-365

Stromatolites are abundant at many horizons in the Proterozoic of Western Australia. Recent advances in knowledge of Proterozoic stratigraphy of the state have provided a more detailed framework for interpreting the stromatolite data than has been available previously. In the 1.7 Ga Earaheedy Group of the Nabberu Basin a characteristic stromatolite assemblage occurs, and within the basin a biostratigraphic succession can be recognized. The assemblage contains several new forms which belong to new groups. The need to erect new groups for these early Proterozoic stromatolites is in agreement with recent studies in Canada, northern Europe and South Africa, and suggests that the problem of ‘younger’ or late Proterozoic stromatolite groups in early Proterozoic rocks mentioned by previous workers is a result of a lack of rigour in defining taxa. Examination of type material is necessary to determine how closely the Earaheedy forms resemble those described from these other regions.In Western Australia some stromatolite forms have a restricted vertical range and similar taxa occur in beds of approximately the same age in widely-separated areas: e.g. Kimberley Group and Earaheedy Group; Scorpion Group and Limbunya, Birrindudu, McArthur, Mt. Rigg and Mt. Albert Groups and Bungle Bungle Dolomite; Tolmer and Bullita Groups; Moora and Bangemall Groups; Kai Ki Beds, Louisa Downs, Mount House and Albert Edward Groups.Stromatolite diversity shows a decline in the number of taxa at about 1.1. Ga in the Bangemall Group. More data are required to determine whether this decline is universal or specific to the Bangemall Group. This study indicates that a stromatolite biostratigraphy for Western Australia is feasible and is consistent with data from other parts of Australia. Thus emphasis on correlation should be placed on the stromatolite form rather than the group, and intercontinental correlations should be attempted only when local biostratigraphic schemes have been firmly established.  相似文献   

Oxyanion Concentrations in Eastern Sierra Nevada Rivers – 3. Boron, Molybdenum, Vanadium, and Tungsten     

Kevin H. Johannesson  W. Berry Lyons  Elizabeth Y. Graham  Kathleen A. Welch 《Aquatic Geochemistry》2000,6(1):19-46

Water samples were collected from 10 locations along the Truckee River system, 14 locations along the Walker River system, and 12 locations along the Carson River, and analyzed for B, Mo, V, W, Na, Cl, and pH. Boron concentrations ranged from approximately 2 mol/kg in the upper reaches of the Truckee River to almost 1,200 mol/kg in Pyramid Lake. Molybdenum, V, and W had concentrations in the nanomolal range; Mo varied from a low of about 12 nmol/kg to a high of 3,200 nmol/kg (Walker Lake); V ranged from 9 nmol/kg to approximately 470 nmol/kg; and W varied from a low value around 0.8 nmol/kg (West Walker River) to 1,030 nmol/kg. The high concentrations of these oxyanion-forming trace elements in the rivers reflects (1) the relative stability of these oxyanions (e.g., MoO₄ ^2-, HVO₄ ^2-, WO₄ ^2-, B(OH)₃, and/or B(OH)₄ ^-) in the alkaline, well oxygenated river and lake waters, (2) contributions of hydrothermal waters (especially for B), and (3) weathering of rocks/regolith with high concentrations of these elements. In the case of Mo, V, and W, each exhibited relatively conservative behavior in the upper, oxygenated reaches of all three rivers. During the study period the region experienced a prolonged drought such that the lower reaches of each river were typified by no flow or stagnant waters and probably low oxygen and/or anoxic conditions (although not measured). Reductive processes occurring in the low flow to stagnant reaches of each river could have led to removal of Mo, V, and W from solution as coprecipitates with Fe monosulfides, or via sorption to Fe oxides/oxyhydroxides and/or organic matter. Boron, however, exhibited essentially no or minor removal from these rivers, and instead was added to each river via B-rich hydrothermal waters (e.g., Steamboat Creek from Steamboat Hot Springs), or by B-rich groundwaters via base-flow during the extensive drought.  相似文献   

Astronomy phenomenological analysis of redshift-distance power laws     

I.E. Segal  J.F. Nicoll 《Astrophysics and Space Science》2000,274(3):503-512

The traditional astronomical literature accepts the linear redshift-distance law on the basis of its internal consistency with accepted models of the history of the universe more than on nontrivial clearly objective tests of the linear law for directly observed quantities. The reluctance to depend on such tests rested historically on the assumed large variation in the intrinsic luminosity of extragalactic objects and a distrust of curve-fitting and statistics. But such tests are eminently feasible on the basis of modern objectively specified samples and up-to-date statistical methodology. This paper compares red-shift distance relations of the form z=k r ^p, for real values of p. Data from the visible, infrared, radio, and X-ray bands are examined. The deviation of predicted and observed apparent magnitudes, (a), and the difference between observed and predicated slope of the magnitude-log (z) plots,(b), are used to compare values of p. In summary, the p=1 values (corresponding to standard linear law) are more deviant than any other value of p, 1<p<=4for test (a) and more deviant than any value of p, 1<p<=3for test (b) except for marginal features in the smallest(radio) sample and in the lowest redshift sample. Bright subsamples and a morphologically homogeneous subsample of elliptic galaxies are also tested with similar results. In contrast, the predications for p=2 are reasonably accurate and close to optimal among all values of p explored. The p=2 case is predicted by the chronometric cosmology and in agreement with the independent analysis of Troitskii. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

A combined paleolimnological/genetic analysis of diatoms reveals divergent evolutionary lineages of Staurosira and Staurosirella (Bacillariophyta) in Siberian lake sediments along a latitudinal transect     

Kathleen R. Stoof-Leichsenring  Nadine Bernhardt  Luidmila A. Pestryakova  Laura S. Epp  Ulrike Herzschuh  Ralph Tiedemann 《Journal of Paleolimnology》2014,52(1-2):77-93

Diatom diversity in lakes of northwest Yakutia (Siberia) was investigated by microscopic and genetic analysis of surface and cored lake sediments, to evaluate the use of sedimentary DNA for paleolimnological diatom studies and to identify obscure genetic diversity that cannot be detected by microscopic methods. Two short (76 and 73 bp) and one longer (577 bp) fragments of the ribulose 1,5-bisphosphate carboxylase/oxygenase (rbcL) gene, encoding the large subunit of the rbcL, were used as genetic markers. Diverse morphological assemblages of diatoms, dominated by small benthic fragilarioid taxa, were retrieved from the sediments of each lake. These minute fragilarioid taxa were examined by scanning electron microscopy, revealing diverse morphotypes in Staurosira and Staurosirella from the different lakes. Genetic analyses indicated a dominance of haplotypes that were assigned to fragilarioid taxa and less genetic diversity in other diatom taxa. The long rbcL_577 amplicon identified considerable diversification among haplotypes clustering within the Staurosira/Staurosirella genera, revealing 19 different haplotypes whose spatial distribution appears to be primarily related to the latitude of the lakes, which corresponds to a vegetation and climate gradient. Our rbcL markers are valuable tools for tracking differences between diatom lineages that are not visible in their morphologies. These markers revealed putatively high genetic diversity within the Staurosira/Staurosirella species complex, at a finer scale than is possible to resolve by microscopic determination. The rbcL markers may provide additional reliable information on the diversity of barely distinguishable minute benthic fragilarioids. Environmental sequencing may thus allow the tracking of spatial and temporal diversification in Siberian lakes, especially in the context of diatom responses to recent environmental changes, which remains a matter of controversy.  相似文献   

Effects of the pharmaceuticals gemfibrozil and diclofenac on the marine mussel (Mytilus spp.) and their comparison with standardized toxicity tests     

Schmidt W  O'Rourke K  Hernan R  Quinn B 《Marine pollution bulletin》2011,62(7):1389-1395

Human pharmaceuticals, like the lipid lowering agent gemfibrozil and the non-steroidal anti-inflammatory drug diclofenac are causing environmental concern. In this study, the marine mussel (Mytilus spp.) was exposed by injection to environmentally relevant and elevated (1 μg/L and 1000 μg/L) concentrations of both compounds and biomarker expression was observed. Gemfibrozil exposure induced biomarkers of stress (glutathione S-transferase and metallothionein) at both concentrations 24 h and 96 h after exposure, respectively. Biomarkers of damage (lipid peroxidation (LPO) and DNA damage) were significantly affected, as well as the biomarker for reproduction, alkali-labile phosphate assay, indicating the potential oxidative stress and endocrine disrupting effect of gemfibrozil. Diclofenac significantly induced LPO after 96 h indicating tissue damage. Additionally standard toxicity tests using the marine species Vibrio fischeri, Skeletonema costatum and Tisbe battagliai showed differences in sensitivity to both drugs in the mg/L range. Results indicate a suite of tests should be used to give accurate information for regulation.  相似文献   

Australian blocking impacts on ocean surface waves     

Marshall  Andrew G.  Hemer  Mark A.  McInnes  Kathleen L. 《Climate Dynamics》2020,54(3):1281-1294

Climate Dynamics - We assess the impact of split-flow blocking in the Australian region on global ocean wind waves using 30&nbsp;years of high-resolution wave data from the CAWCR wave model...  相似文献   

The Kuroshio Extension and its recirculation gyres     

Steven R. Jayne  Nelson G. Hogg  Stephanie N. Waterman  Luc Rainville  Kathleen A. Donohue  D. Randolph Watts  Karen L. Tracey  Julie L. McClean  Mathew E. Maltrud  Bo Qiu  Shuiming Chen  Peter Hacker 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(12):2088-2099

This paper reports on the strength and structure of the Kuroshio Extension and its recirculation gyres. In the time average, quasi-permanent recirculation gyres are found to the north and south of the Kuroshio Extension jet. The characteristics of these recirculations gyres are determined from the combined observations from the Kuroshio Extension System Study (KESS) field program (June 2004–June 2006) and include current meters, pressure and current recording inverted echo sounders, and subsurface floats. The position and strength of the recirculation gyres simulated by a high-resolution numerical model are found to be consistent with the observations. The circulation pattern that is revealed is of a complex system of multiple recirculation gyres that are embedded in the crests and troughs of the quasi-permanent meanders of the Kuroshio Extension. At the location of the KESS array, the Kuroshio Extension jet and its recirculation gyres transport of about 114 Sv. This represents a 2.7-fold increase in the transport of the current compared to the Kuroshio's transport at Cape Ashizuri before it separates from the coast and flows eastward into the open ocean. This enhancement in the current's transport comes from the development of the flanking recirculation gyres. Estimates from an array of inverted echo sounders and a high-resolution ocean general circulation model are of similar magnitude.  相似文献   

Vertical distribution of first stage larvae of the blue crab,Callinectes sapidus,at the mouth of Chesapeake Bay     

Anthony J. Provenzano  John R. McConaugha  Kathleen B. Philips  David F. Johnson  John Clark 《Estuarine, Coastal and Shelf Science》1983,16(5):489-499

The vertical distribution of stage I blue crab larvae, near the mouth of Chesapeake Bay, was examined over four diurnal cycles. Each of two stations was occupied for 30 hours twice during the summer of 1979.On each of the four cruises, peak larval abundance occurred after a night time high slack tide, suggesting a synchronized hatch of blue crab larvae. 90–99% of all larvae collected were taken in the neuston layer. The apparent timing of the hatches to coincide with the beginning of an ebb tide and the concentration of larvae in the neuston layer strongly suggests seaward transport of these early stage larvae and the probability of offshore development.  相似文献