Evaluating new fault-controlled hydrothermal dolomitization models: Insights from the Cambrian Dolomite,Western Canadian Sedimentary Basin     

Ardiansyah Koeshidayatullah  Hilary Corlett  Jack Stacey  Peter K. Swart  Adrian Boyce  Hamish Robertson  Fiona Whitaker  Cathy Hollis 《Sedimentology》2020,67(6):2945-2973

Fault-controlled hydrothermal dolomitization in tectonically complex basins can occur at any depth and from different fluid compositions, including ‘deep-seated’, ‘crustal’ or ‘basinal’ brines. Nevertheless, many studies have failed to identify the actual source of these fluids, resulting in a gap in our knowledge on the likely source of magnesium of hydrothermal dolomitization. With development of new concepts in hydrothermal dolomitization, the study aims in particular to test the hypothesis that dolomitizing fluids were sourced from either seawater, ultramafic carbonation or a mixture between the two by utilizing the Cambrian Mount Whyte Formation as an example. Here, the large-scale dolostone bodies are fabric-destructive with a range of crystal fabrics, including euhedral replacement (RD1) and anhedral replacement (RD2). Since dolomite is cross-cut by low amplitude stylolites, dolomitization is interpreted to have occurred shortly after deposition, at a very shallow depth (<1 km). At this time, there would have been sufficient porosity in the mudstones for extensive dolomitization to occur, and the necessary high heat flows and faulting associated with Cambrian rifting to transfer hot brines into the near surface. While the δ¹⁸O_water and ⁸⁷Sr/⁸⁶Sr ratios values of RD1 are comparable with Cambrian seawater, RD2 shows higher values in both parameters. Therefore, although aspects of the fluid geochemistry are consistent with dolomitization from seawater, very high fluid temperature and salinity could be suggestive of mixing with another, hydrothermal fluid. The very hot temperature, positive Eu anomaly, enriched metal concentrations, and cogenetic relation with quartz could indicate that hot brines were at least partially sourced from ultramafic rocks, potentially as a result of interaction between the underlying Proterozoic serpentinites and CO₂-rich fluids. This study highlights that large-scale hydrothermal dolostone bodies can form at shallow burial depths via mixing during fluid pulses, providing a potential explanation for the mass balance problem often associated with their genesis.  相似文献   

Observations of resuspended diatoms in the turbid tidal edge     

Cathy H. Lucas 《Journal of Sea Research》2003,50(4):301-308

Observations of resuspended diatoms in the shallow waters (<60 cm) of the turbid tidal edge are described for single sites on two tidal flats–the Molenplaat in the Westerschelde estuary, and the Hond in the Ems-Dollard estuary, The Netherlands. High concentrations of chlorophyll-a (chl-a) were observed in the trailing edge of the ebbing tide in water depths of <20 cm, after which concentrations decreased markedly. Peak mean values were 19 μg chl-a l⁻¹ in 10 cm of water at the Molenplaat, and 45 μg chl-a l⁻¹ in 5 cm of water at the Hond. Similar trends were observed on the flooding tide, although peak values were far less pronounced (6 and 30 μg chl-a l⁻¹ respectively). Microscopic examination of the diatom community within the turbid tidal edge at the Molenplaat revealed that peaks in biomass were caused by suspended benthic diatoms, as well as the large centric diatom Coscinodiscus sp., particularly on the ebb tide. Planktonic diatoms other than Coscinodiscus sp. were more randomly distributed and did not appear to follow any particular trend. It would seem that as the tide recedes, resuspended benthic diatoms and large Coscinodiscus sp. cells become concentrated in the shallow water. However, the virtual absence of Coscinodiscus sp. from the leading edge of the flooding tide suggests that most of the resuspended cells do not settle to the seabed, but are washed away into the channels. The small peak of benthic diatoms at the leading edge of the flood tide is most likely resuspended locally from the sediment, along with large numbers of diatom frustules.  相似文献   

Use of the Stinkbug,Encosternum delegorguei (Hemiptera,Tessaratomidae), for Food and Income in South Africa     

Cathy M. Dzerefos  Ed T. F. Witkowski  Rob Toms 《社会与自然资源》2014,27(8):882-897

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Ethnic enterprises and community development     

Cathy Yang Liu  Jonathan Miller  Qingfang Wang 《GeoJournal》2014,79(5):565-576

Ethnic enterprises are growing rapidly in urban areas across the United States. Anecdotal evidence from around the country reports many success stories of how ethnic businesses transform communities; however, researchers have not provided a systematic review of the role of ethnic businesses in community developing. In practice, ethnic businesses have not been formally incorporated in local planning and development process. This article provides a systematic review of the multi-faceted ways ethnic businesses contribute to community building and neighborhood development. In addition to surveying the current literature, we also chose three communities for a focused review: Buford Highway in Atlanta, Monterey Park in Los Angeles, and Sunset Park in New York. A framework is developed to evaluate the economic, physical, social/cultural, and political effects that ethnic businesses exert on communities. We find that ethnic businesses can serve local economic interests and community-level cohesion and accrue economic, social, physical, and political benefits to their respective communities. These include serving the unmet market needs of certain neighborhoods and households, creating job opportunities and generating revenues, revitalizing and fueling the commercial development of abandoned communities, organizing and promoting social life and cultural diversity, as well as contributing their collective interest and voice in local communities. We argue that ethnic businesses should be better incorporated into urban policies in community economic development.  相似文献   

A tipping bucket flowmeter for roadside gully runoff     

G. E. Hollis  J. C. Ovenden 《水文研究》1987,1(4):391-396

A tipping bucket flowmeter designed for the measurement of inflows to roadside gully pots is described. It is braced within the pot above the liquor and the runoff is fed to it via a glass fibre funnel and a hose. Whilst it can be calibrated to only 0·71 s^?1, it is very effective at low flows and has a number of advantages over the well known Institute of Hydrology Gully Meter. Its use at Redbourn, Hertfordshire for roads on highly permeable soils shows that for both rainfall and artificial irrigation the ‘losses’ are very large and highly variable even within a single housing estate road.  相似文献   

One year irrigation experiment to assess losses and runoff volume relationships for a residential road in hertfordshire,England     

G. E. Hollis  J. C. Ovenden 《水文研究》1988,2(1):61-74

Six sections of a residential road (75 mm bituminous macadam over 200mm lean mix concrete over 100 mm hoggin with a recent surface dressing of 10 mm granite chippings and K1-70 binder) that drain to individual instrumented gully pots were irrigated along the kerb and then over the whole road approximately monthly for a year. The aim was the determination of terminal infiltration losses, initial losses, percentage runoff, and infiltration curves for the kerb and road surface. The results were not as expected from the literature. There is an annual cycle of infiltration losses at the kerb with a winter peak caused by frost action that is 3.2 times greater than the terminal loss rate at kerbs in summer. The terminal loss rate for an ‘average catchment’ was 6.4251 min^?1 from the road surface and 14.251 min^?1 in summer and 46.281 min^?1 in winter at the kerb. Evaporation was usually more than an order of magnitude less significant than infiltration. The wide variation in initial losses before runoff commenced was inexplicable. Two sections of road behaved in the classic manner with initial losses averaging 0.8 mm, two other catchments had highly variable initial losses in the range 1.2 to 8.8mm, and the last two pieces of road were even more erratic. The percentage runoff for those irrigations of over 15 mm of equivalent rainfall was never more than 10 per cent. The maximum per cent runoff was around 50 per cent following 10 mm of equivalent rainfall for kerbside irrigation and only 5 mm of irrigation over the whole road. There were no significant simple or multiple regression relationships between percentage runoff from the kerb or the whole road irrigations and irrigation amount, slope, UCWI, and SMD. Infiltration curves, for kerb and road irrigation, were so diverse that they do not represent the ‘simple impervious surfaces’ envisaged at the start of the experiment and described in the literature. Since the artificial irrigation of kerbs and roads has failed to substantiate existing theory, these experiments should be repeated at a variety of sites with a high rate of irrigation.  相似文献   

Spatial and temporal distribution of heavy metal concentrations in mussels (Mytilus edulis) from the Baie des Chaleurs, New Brunswick, Canada     

Fraser M  Surette C  Vaillancourt C 《Marine pollution bulletin》2011,62(6):1345-1351

Previous studies on heavy metal contamination of the Baie des Chaleurs focus only on industrial centers and overlooked the ecosystem as a whole. To fill this gap, the objective of this study is to establish a baseline of the spatio-temporal distribution of heavy metals in mussels from the Baie des Chaleurs based on the ecosystem approach. Our results show, for the first time, a cadmium contamination in mussels across the south coast of the Baie des Chaleurs and not only in industrial centers. Our results also confirm previous studies showing heavy metal contamination of the Belledune area. This study demonstrates that the use of the ecosystemic approach is essential to obtain a comprehensive picture of environmental contamination in marine ecosystems.  相似文献   

Ca II resonance lines in non-homogeneous chromospheres     

Herbert A. Beebe  Hollis R. Johnson 《Solar physics》1969,10(1):79-87

Profiles of the K line of Caii are computed for a two component solar chromosphere, chosen to simulate with a simple geometry the chromospheric supergranular network. Each component rises above the BCA photosphere, the boundary component representing the bright network with a sharp temperature rise and the cell component representing the darker region with an extended temperature minimum. Theoretical intensity profiles of the Can K core, calculated as weighted averages over the projected areas of the components, are produced for = 0.6 and 0.3. The line source function and the optical depth are obtained from a self-consistent treatment of the steady state and radiative transfer equations, with complete redistribution assumed for scattering in the line. The atomic model consists of two bound levels and a continuum. It is found that a 4600 K minimum can lead to the successful theoretical prediction of the observed limb darkening and 4300 K radiation temperature of the K1 feature only when very large values of turbulent velocity are assumed to exist in the cell region.Publications of the Goethe Link Observatory, Indiana University, No. 95.  相似文献   

A study of objective methods for water mass analysis,applied to the Iceland Basin     

de Boer  Cathy J.  van Aken  Hendrik M. 《Ocean Dynamics》1995,47(1):5-22

Ocean Dynamics - Cluster analysis and principal component analysis have been applied to multi-parameter hydrographic data from the Iceland Basin. The results indicate that both objective methods...  相似文献   

THE NEGOTIATION OF SPACE AMONG SEX WORKERS IN CEBU CITY, THE PHILIPPINES     

Cathy McIlwaine 《Singapore journal of tropical geography》1997,17(2):150-164

The paper examines the experiences of space among sex workers in Cebu City, a major service and commercial centre in the Visayan region of the Philippines. It explores the issue of space from a number of perspectives and scales: first, at the national level in terms of migration patterns among sex workers; second, at the local level in relation to how sex workers experience and construct urban spaces through residence and working patterns; and finally, from a community perspective, the nature of domestic spaces among these women. The underlying theme of the paper centres around the contradictory ways in which social opprobrium is often reflected in spatial seclusion among sex workers. On the one hand, they are constrained in their experiences of space. On the other, the construction of their own particular spaces reflects a high degree of resourcefulness and resistance. This is corroborated further by the fact that involvement in the sex industry creates a different set of spatial aspirations and awareness among sex workers compared with those of the wider population.  相似文献