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71.
Christine S. Lane Maja Andrič Victoria L. Cullen Simon P.E. Blockley 《Quaternary Science Reviews》2011,30(9-10):1013-1018
The discovery of sites preserving tephra layers from multiple volcanic centres is key to constructing a single European tephrostratigraphic framework for the Late Quaternary. Until now, the tephrostratigraphy of Europe has been divided into two halves: sites in the North Atlantic and northern Europe regions link the Icelandic, Eifel, and the Massif Central volcanic histories; whilst sites in southern Europe record the sequence of tephra layers produced by circum-Mediterranean volcanic provinces. The missing link, able to tie together these two halves, is found in the tephrostratigraphic record of Lake Bled, Slovenia.Lake Bled, in the Julian Alps, Slovenia, holds a high resolution multi-proxy palaeoenvironmental archive for the Lateglacial of south-central Europe. Cryptotephra investigations have revealed three tephra layers: two closely spaced within Younger Dryas stadial sediments and one shortly after the start of the Bølling-Allerød interstadial warming. Two of the tephra layers (Bld_T120 and Bld_T240) are of Campanian origin and are correlated to deposits of the Pomici Principali (PP) and Neapolitan Yellow Tuff (NYT) eruptions, respectively. The third layer (Bld_T122) correlates to the Icelandic Vedde Ash (VA), extending the known fallout of this widespread marker layer farther to the southeast.The Lake Bled record also allows the stratigraphic relationship and relative ages of the VA and the PP eruption to be discerned for the first time. Whilst existing numerical age estimates for these two deposits are indistinguishable within errors, their close occurrence in the same lacustrine sediment sequence shows that the VA was erupted shortly prior to the PP eruption.The tephrostratigraphy of Lake Bled developed here helps us to tie together regional volcanic stratigraphies into a broader, continental-scale lattice of sites, with the potential to allow the transfer of dates between remote sequences and the construction of relative chronologies, beneficial in particular for environmental and archaeological research. 相似文献
72.
Michael E. Burns Philip J. CurrieRobin L. Sissons Victoria M. Arbour 《Cretaceous Research》2011,32(2):174-186
Four juvenile specimens referable to Pinacosaurus grangeri (Ankylosauria: Dinosauria) are described from the Campanian (Upper Cretaceous) locality Bayan Mandahu in northern Inner Mongolia Autonomous Region (People’s Republic of China). All the specimens preserve the skulls as well as, in some cases, mandibles, postcrania, and osteoderm. They are not taphonomically deformed by expanding matrix distortion, unlike many Gobi specimens, including the holotype of P. grangeri. Bayan Mandahu is also the type locality for Pinacosaurus mephistocephalus. The proximity in space and time of these two closely related species warrants a generic and specific revision for Pinacosaurus. The distinction of the two species is based on characters of the squamosal dermal elaborations, cranial roof posterior to the orbits, premaxillary notch, and distal margin of the ilium. Although a relatively well-represented ankylosaur taxon, the phylogenetic position of Pinacosaurus has not been unequivocally resolved. A new analysis recovers Pinacosaurus as the most basal member of the Ankylosaurinae. 相似文献
73.
Meredith L. McPherson Victoria J. Hill Richard C. Zimmerman Heidi M. Dierssen 《Estuaries and Coasts》2011,34(6):1150-1160
Water column optical properties of Greater Florida Bay were investigated in the context of their impacts on seagrass distribution.
Scattering played an important role in light attenuation throughout the shallow water system. The northwest region was characterized
by an absence of seagrasses and the highest scattering by particles, mostly from resuspended carbonate sediments. Higher seagrass
densities were observed in the open waters just north of the Florida Keys, where absorption coefficients were dominated by
colored dissolved organic material and scattering was lower than in the northwest region. Patchy dense seagrass meadows were
observed in the clear waters south of the Keys where scattering and absorption were low and contributed equally to light attenuation.
In general, seagrasses were observed in areas where >7.5% of surface irradiance reached the plants and where optical properties
were not dominated by scattering. Although the prevention of eutrophication and nuisance algal blooms may be necessary for
preserving seagrass meadows in this system, our observations and model calculations indicate that nutrient control alone may
be insufficient to permit seagrass recolonization if optical properties are dominated by particulate scattering from resuspended
sediments. 相似文献
74.
Realism is a philosophy of science wherein researchers attempt to identify structures and agents present in society and how they tend to act. Philosophical debates over realism, which have often been confrontational, have clouded the practical contributions of a realist approach to substantive research. The latter is the focus of this paper. Many realists combine several bodies of theory to explain the complexity of societies. In using these theories, realists clarify the distinctions between questions concerning observable phenomena and the processes that create them. A realist approach illuminates the elusive nature of social “facts” and the problems of meaning, interpretation, and understanding in researching the social world. 相似文献
75.
Contrasting conditions preceding MIS3 and MIS2 Heinrich events 总被引:2,自引:0,他引:2
Elsa Jullien Francis E. Grousset Sidney R. Hemming Victoria L. Peck Ian R. Hall Cdric Jeantet Isabelle Billy 《Global and Planetary Change》2006,54(3-4):225-238
This paper presents an integrated multi-tracer study performed on piston cores recovered in the glacial ice-rafted detritus belt, stretching from Newfoundland to the Irish margin across the North Atlantic (40–55°N), in order to compare in detail the internal structure of each Heinrich event (HE). These tracers are IRD counts (quartz, dolomite, volcanic grains), their Nd isotopic composition and Ar–Ar datings of individual hornblende grains. A focus on the detailed structure of HE confirms that all intervals of massive sediment flux, specifically Heinrich layers HL1-to-5 (HLs), were dominated by North American, Laurentide ice-sheet surges from Hudson Strait, that are evident as far east as the Bay of Biscay (European margin). The sequences of events leading up to the HLs, however, present significant dissimilarities. One important difference is that HL2 and HL1 were preceded by “precursor events” (increases in the number of lithic grains per gram from non-Laurentide sediment sources). Sediment debris derived from near-simultaneous iceberg releases originating from the European ice-sheet are only detectable close to the European margin. In contrast there are no comparable precursor events before HL5 and HL4. This observation implies that precursor events are unlikely to be mechanistically linked to the triggering of HEs. The similarity of the HLs, against contrasting background conditions, is a significant observation that should add constraints to their origin. 相似文献
76.
Victoria R. Propp Susan J. Brown Pamela Collins James E. Smith James W. Roy 《Ground Water Monitoring & Remediation》2022,42(1):50-64
Leachate-contaminated groundwater from historical municipal landfills, typically lacking engineered liners and leachate collection systems, poses a threat to nearby urban streams, particularly to benthic ecosystems. Effective monitoring and assessment of such sites requires understanding of the spatial patterns (i.e., two-dimensional footprint) of contaminated groundwater discharge and associated controlling factors. However, discharges from groundwater contaminated by modern wastewater can complicate site assessments. The objectives of this study were to (1) demonstrate the use of artificial sweeteners (AS): saccharin (SAC), cyclamate (CYC), acesulfame (ACE), and sucralose (SUC), to distinguish groundwater discharge areas influenced by historic landfill leachate (elevated SAC and sometimes CYC; low ACE and SUC concentrations) from those influenced by wastewater (high ACE and SUC concentrations), and (2) investigate contaminant discharge patterns for two gaining urban stream reaches adjacent historic landfills at base flows. Contaminant discharge patterns revealed by the AS were strongly controlled by hyporheic flow (low AS concentrations), particularly for the straight reach, and stream sinuosity, particularly for the meandering reach. These patterns were different and the contaminant footprint coverage (<25% of streambed area) much less than most past studies (typically >50% coverage), likely due to the homogeneous streambed-aquifer conditions and shallow, narrow landfill plume in this setting. 相似文献
77.
Victoria?ManetaEmail author Don?R.?Baker William?Minarik 《Contributions to Mineralogy and Petrology》2015,170(1):4
New experimental data on the solubility of lithium (Li) at spodumene (LiAlSi2O6) and petalite (LiAlSi4O10) saturation at 500 MPa and 550–750 °C reveal evidence for lithium supersaturation of pegmatite-forming melts before the formation of Li-aluminosilicates. The degree of Li enrichment in granitic melts can reach ~11,000 ppm above the saturation value before the crystallization of Li-aluminosilicate minerals at lower temperatures. Comparison of the experimental results with the spodumene-rich Moblan pegmatite (Quebec) is consistent with extreme Li enrichment of the pegmatite-forming melt prior to emplacement, which cannot be explained with equilibrium crystallization of Li-aluminosilicates from a common granitic melt. The results of this study support the model of disequilibrium fractional crystallization through liquidus undercooling as the most plausible mechanism for the generation of such Li-rich ore resources. 相似文献
78.
Victoria Ochoa Carmen Riva Melissa Faria Carlos Barata 《Marine pollution bulletin》2013,66(1-2):135-142
Marine bivalves such as oysters are widely used as bioindicators to monitor marine coastal pollution. This study aimed to use B-esterase activity responses in oysters (Crassostrea gigas) cultured in Ebro Delta bays to monitor environmental effects of pesticides. The B esterases investigated were acetylcholinesterase, propionylcholinesterase, and carboxylesterase and their activities were measured in adductor muscle and gills from oysters transplanted in Ebro Delta bays where the are traditionally grown. Enzyme activities were related with physico-chemical parameters and pesticide levels measured in water. Cholinesterase activities measured in gills were unaffected across sites and periods. Conversely, carboxylesterase activities in oyster gills varied across periods and sites and were negatively correlated with residue levels of organophoshporous and carbamate pesticides in water. Therefore, inhibition of carboxylesterase activities can be considered a good indicator of exposure to anti-cholinergic pesticides in oysters. 相似文献
79.
Classroom responses of New Zealand school teachers following the 2011 Christchurch earthquake 总被引:1,自引:1,他引:0
Following a damaging magnitude 6.3 earthquake in Christchurch, New Zealand on February 22, 2011, an unprecedented number of displaced school children were enrolled temporarily or permanently in new schools throughout New Zealand. This study utilized accounts from primary school teachers in New Zealand, derived from focus groups scheduled in March and April 2011 for an evaluation of a disaster preparedness teaching resource, to examine how these disasters impacted individuals and schools outside of Christchurch. The educators’ focus group accounts provide an illustration of classroom responses including providing emotional support to displaced children, informal classroom discussions, curricular responses, addressing disaster rumors, and information seeking through peers. Some recommendations are provided on ways to support teachers’ important roles in disaster recovery, including targeting evidence-based guidance and teaching resources to schools enrolling displaced children, dispelling disaster rumors through schools and facilitating peer mentoring among teachers. An overarching lesson is that communities would benefit from teachers being better equipped to provide emotional support and responsive disaster education to children after disasters. 相似文献
80.
Victoria González-Carman Natalia Machain Diego Albareda Hermes Mianzan Claudio Campagna 《Marine Policy》2012
This paper explores conservation policy pertinent to three species of marine turtles affected by fisheries, while crossing jurisdictions in their seasonal migrations through the SW Atlantic, particularly the Argentine waters. This case study reviews local legal and institutional frameworks for Argentina and concludes that tools are in place to monitor and mitigate the negative impact of bycatch on the populations. Argentina is signatory of the most relevant international treaties aimed at protecting transboundary species (e.g. Inter-American Convention for the Protection and Conservation of Sea Turtles, Convention on the Conservation of Migratory Species of Wild Animals). Legislation also exists at the federal and provincial levels. Yet, accidental captures continue to occur due to weaknesses in enforcement and the low priority that conservation has in fisheries management decisions. Some urgent practical actions supported by policy are suggested: (a) placement of on-board observers in coastal fishing fleets, (b) application of existing mitigation measures to reduce bycatch, (c) design of a national plan of action for marine turtles in Argentina, and (d) development of a regional plan between Argentina, Brazil and Uruguay. Stakeholder involvement, especially the fishing sector but also the civil society, would be important to energize practical and effective conservation decisions. The example of Argentina is typical for the region and may apply to other countries as well. The conservation community requires investing more in the application of policy, concomitant with perfecting legal tools. 相似文献