Stratigraphy and thermoluminescence dating of Late Glacial cover sand in Denmark     

Else Kolstrup  Rainer Grün  Vagn Mejdahl  Susan C. Packman  Ann G. Wintle 《第四纪科学杂志》1990,5(3):207-224

In western Jutland deposits with a texture and structure similar to Dutch cover sands have been found. Investigations have been carried out on the lithology and the lithostratigraphic sequences. Pollen analysis is used for biostratigraphic correlation, and ages have been obtained by the radiocarbon method as well as by thermoluminescence techniques using both quartz and eldspar. The five sites are presented separately and the data are integrated into a general stratigraphic outline of the Late Glacial cover-sand sequence in Jutland. During the latest part of the Upper Pleniglacial and the earliest Late Glacial, older cover-sand type was deposited. Locally this sediment was also deposited during the later parts of the Late Glacial. Younger cover-sand type was deposited primarily during the Early Dryas and Late Dryas, but some sand of this type was also laid down during the Allerød and the earliest Holocene. The palaeobotanical records are discontinuous, but plant growth was probably present throughout the Late Glacial; only during the Altered did the deposition of sand decrease long enough to allow a relatively stable vegetational development. The investigation shows that the sequence of events in Jutland is similar to the Dutch record.  相似文献   

Rock avalanching into a landslide-dammed lake causing multiple dam failure in Las Conchas valley (NW Argentina) — evidence from surface exposure dating and stratigraphic analyses   总被引：3，自引：1，他引：2  

Reginald?L.?HermannsEmail author  Samuel?Niedermann  Susan?Ivy-Ochs  Peter?W.?Kubik 《Landslides》2004,1(2):113-122

Generally landslide dams which exist for several hundreds to thousands of years are considered as stable. We show with an example from the Argentine Andes that such dams can exist for several thousands of years but still may fail catastrophically. Multiple rock avalanches impounded two lakes with surface areas of ~8 km² and ~600 km², respectively, in Las Conchas valley, NW Argentina. Surface exposure dating (SED) by ¹⁰Be of the rock-avalanche deposits or landslide scars indicates that these landslides occurred at 15,300±2,000 yr and 13,550±900 yr. The dams were stable during a strong earthquake, as suggested by seismites within related lake sediments and by multiple coeval landslides in this region, which occurred at ~7.5 kyr. However, when a further rock-avalanche fell into the lower, smaller lake at 4,800±500 yr the dam downriver was destroyed, presumably by the resulting tsunami wave. The resulting flood also destroyed an additional rock-fall dam which had formed at ~5,630 yr ¹⁴C cal BP 30 km downriver. The new dam formed by the second rock avalanche was eroded prior to 3,630 yr ¹⁴C cal BP. This dam erosion coincides with an important climatic shift towards more humid conditions in the Central Andes. Our results show that instead of direct effects of strong seismicity on landslide dams, (1) landsliding into a landslide-dammed lake, (2) abrupt hydrological changes, and (3) climate change towards conditions related to enhanced run-off are processes which can produce failures of quasi-stable natural dams.  相似文献   

Estimating mortality in natural assemblages of oysters     

Susan E. Ford  Meagan J. Cummings  Eric N. Powell 《Estuaries and Coasts》2006,29(3):361-374

To evaluate methods for calculating mortality in bivalve molluscs, we analyzed historical data from dredge surveys of both planted and natural oyster (Crassostrea virginica) grounds in Delaware Bay to compare total box-count mortality estimates with those made by accumulating short-term mortality rates obtained from fresh boxes identified by shell condition and degree of fouling. Box-count and cumulative-mortality patterns and values agreed best on grounds with planted oysters, where a cohort with very few dead oysters was broadcast on previously cleaned bottom and was followed over time. This situation is analogous to an artificially created reef with oysters either deployed or naturally set on it. When deaths predominated in late summer and early autumn, the two estimates were similar throughout the following year; when mortality was greatest in spring or early summer, the estimates were similar only through autumn of the same year. Correspondence was much weaker on natural beds, where new individuals constantly recruited to the population and variable numbers of boxes were always present. Nevertheless, total box-count mortality estimates made during autumn stock surveys were significantly correlated with cumulative mortalities calculated for the preceding year. We also estimated disarticulation rates of artificially created boxes by deploying them at three seasons and eight sites in Delaware Bay. Disarticulation time depended on the length of exposure at summer temperatures, with the average time to 50% disarticulation for boxes deployed in spring and in summer being 225 and 345 days, respectively. Disarticulation rates increased with decreasing size, and increasing salinity and temperature. Finally, we compared total box-count and cumulative-mortality estimates with those made using the disarticulation data. Annual averages for the three methods were within 5 percentage points of each other. Our data indicate that total box-count mortality estimates from fall stock surveys can provide a reliable index to total mortality for the previous year, although it cannot describe the seasonal patterns obtainable using the cumulative-mortality method. *** DIRECT SUPPORT *** A02BY003 00003  相似文献   

The liminality of training spaces: Places of private/public transitions     

Susan Buckingham  Elodie Marandet  Fiona Smith  Emma Wainwright  Marilyn Diosi 《Geoforum》2006,37(6):895-905

This paper draws upon research, conducted for the London West Learning and Skills Council, on the training experiences of women with dependent children. One of the striking revelations of the research, we suggest, is the way in which training spaces are used and perceived by women, which are often at odds with government intentions. To help make sense of women’s use of, and motivation for, training we utilise the concept of ‘liminality’ and the private/public imbrication to explain the ways in which women use, or are discouraged from using, training spaces. Further, how the varied and multiple uses women in our research have put training to in their own lives has encouraged us to rethink the relationship between the private and the public more generally. In the light of this, we suggest that training and the places in which training take place, have been neglected processes and spaces within feminist geography and might usefully be explored further to add to an extensive literature on women’s caring and domestic roles and their role in the paid workplace.  相似文献   

Oxygen consumption rates in pelagic sediments from the Central Pacific: First estimates from microelectrode profiles     

Clare E Reimers  Susan Kalhorn  Steven R Emerson  Kenneth H Nealson 《Geochimica et cosmochimica acta》1984,48(5):903-910

Oxygen profiles in pelagic sediments from the Manganese Nodule Program calcareous and siliceous ooze sites (MANOP sites C and S) in the central Pacific Ocean were measured with microelectrodes and are used to predict oxygen consumption rates beneath the sediment-water interface. We explain possible artifacts which occur during sample recovery and argue that minimum estimates of 0.083 and 0.025 μ moles $\text{O}{}_2\text{cm}{}^2\text{day}$ (C and S, respectively) can be calculated from the data. These oxygen consumption rates are in good agreement with in situ respirometer measurements previously reported for comparable sediments in the north Pacific, but previous estimates based on modeling of pore water nitrate profiles at both sites are two to five times smaller than our minimum fluxes. The differences in oxygen fluxes calculated by the two methods are probably in part due to uncertainty in the assumptions inherent in the nitrate model. However, non-steady state fluctuations in particulate organic matter fluxes could also be a reason for the disparity.  相似文献   

Geophysical evidence for post-Miocene rotation of the island of Viti Levu,Fiji, and its relationship to the tectonic development of the North Fiji Basin     

Alexander Malahoff  Stephen R. Hammond  John J. Naughton  David L. Keeling  Ronald N. Richmond 《Earth and Planetary Science Letters》1982,57(2):398-414

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Symposium über Fragen der Cyanophytentaxonomie im Seenforschungsinstitut der ETHZ/EAWAG in Kastanienbaum (Schweiz), 2.–15. August 1979 Verhandlungsbericht     

Alfons Zehnder  Dr. J. Komárek  Prof. Dr. S. Golubić  Prof. Dr. R. Y. Stanier  Dr. J. Komárek  Dr. J. Ludvík  Dr. L. Kováčik  Dr. Asta Almestrand  Prof. Dr. P. Compère  Dr. D. Mollenhauer  Dr. F. Hindák  Dr. T. P. Chang  Dr. Nagaraj Jeeji Bai  C. V. Seshadri  Dr. M. -E. Meffert  Dr. R. Oberhäuser  Dr. J. Overbeck  Dr. F. Hindák  Susan E. Campbell  Dr. Jaroslava Komárková  Dr. U. Uehlinger  Dr. F. Schanz  Dr. Alfons Zehnder 《Aquatic Sciences - Research Across Boundaries》1983,45(1):267-310

The 8th Symposium of the International Association for Cyanophyte Research IAC was attended by 29 specialists from 11 countries. The 19 oral presentations and discussions centered on the following themes: The basic principles of cyanophyte taxonomy (3 lectures), systematic problems of certain taxonomic groups (5 lectures), morphology (6 lectures) and ecology (5 lectures). The intensive discussions between representatives of the classical (european) taxonomic treatment of cyanophytes (based on morphological and ecological characteristics) and those representing the bacteriological study of ‘cyanobacteria’ were especially valuable. The central theme of the meeting was, however, the mutual microscopic study and discussion of problematic blue-greens from natural habitats, that were mostly collected during the three field trips into different areas of central Switzerland (Grimsel-Gotthard-Nufenen. Klewenalp. Gerzensee).   相似文献   

Factors Influencing Recreational Boaters’ Intentions to Comply with Right Whale Regulations in the Southeastern United States     

Nancy Montes  Robert Swett  Susan K. Jacobson  Charles Sidman 《社会与自然资源》2018,31(4):473-488

Regulations for boaters can help mitigate adverse effects on threatened marine mammals. One management tool to protect endangered North Atlantic right whales is a 460-m distance restriction rule for all vessels. This study is the first effort to analyze factors that influence recreational boaters’ intentions to comply with this regulation. Using the theory of planned behavior, we analyzed 362 mail surveys of recreational boaters using the offshore waters of the southeastern United States. We found that two constructs of the theory significantly explained 58% of the intention to comply with the rule: (1) positive attitude toward the rule and (2) stronger belief that other people are complying. Boaters recommended increasing knowledge about whales to improve compliance, but they were divided with respect to increasing fines for violators to increase compliance. This information can be useful for designing outreach strategies to protect whales.  相似文献   

The 2012 Olympic Learning Legacy Agenda – the intentionalities of mobility for a new London model     

Susan Moore  Mike Raco  Ben Clifford 《Urban geography》2018,39(2):214-235

This paper investigates the emergence of a Learning Legacy Agenda (LLA) in the wake of the London 2012 Olympic Games as a governmental tool for the dissemination of urban development and infrastructure project delivery best practice. Focusing on the inception, coordination and implementation of the LLA we outline the intentionalities of mobility that underpin its formation and appropriation and suggest how this points to the emergence of a new “London model” of development and governance. Three intentionalities of knowledge capture, public duty and extra-local salience are unpacked to demonstrate the range of ways in which the bureaucratically initiated LLA banner has been used by various development actors and organisations to validate their existing practices. The case study of the LLA as an institutionalised governance apparatus is used to analyse the impact of specific forms of social relations on the ways in which “models” are produced, what their content consists of, how dominant agendas and narratives co-evolve with the priorities of an assemblage of actors and the processes of selective abstraction used to curate particular messages and forms of fixed and potentially mobile knowledge, yet dubious claims of “learning”.  相似文献   

Examination of diatom-based changes from a climatically sensitive prairie lake (Saskatchewan, Canada) at different temporal perspectives     

Kathleen R. Laird  Astrid Michels  Chloë T.L. Stuart  Susan E. Wilson  William M. Last  Brian F. Cumming 《Quaternary Science Reviews》2007,26(25-28):3328-3343

Paleoclimatic records from the climatically sensitive Canadian prairies are relatively rare due to the scarcity of study sites with continuous Holocene stratigraphic sequences. Oro Lake, a meromictic lake in the dry grasslands of Saskatchewan (Canada), contains a continuous Holocene diatom record spanning the last 10,000 years. Here we present analyses at three different time scales and resolution: (1) 1–3 yr resolution of the past 80 years, (2) century-scale analysis of the Holocene, and (3) decadal-scale analysis of the past 7000 years. Recent changes in the diatom assemblages and their respective salinity inferences were significantly related to measured effective moisture (precipitation minus evaporation, P−ET). The droughts of the 1930s, and a wet period during the 1950s are clearly evident in the diatom record, suggesting the Oro Lake record contains a sensitive archive of past climatic conditions. Century-scale analysis of the diatom record during the Holocene is consistent with a cool and moist climate in the early Holocene (prior to ca 9700 cal yr BP, 8600 ¹⁴C yr BP). An abrupt increase in diatom-inferred salinity at 9600 cal yr BP (8500 ¹⁴C yr BP) indicates the onset of an arid climate, with continuing arid conditions throughout the mid-Holocene. Decadal-scale analysis of the past 7000 years suggests that the mid-Holocene was more complex, with extended periods of increased variability in precipitation, particularly between ca 5800–3600 cal yr BP (5000–3200 ¹⁴C yr BP) which is characterized by intervals of increased effective moisture. The past 2000 years is characterized by reduced salinities and generally wetter conditions in comparison to the mid-Holocene. The combination of the different scales of analyses in this study provides a detailed account of the dynamic nature of climate from sub-decadal to millennial scale in the Oro Lake region within the Palliser Triangle. Climate model predictions suggest that the Canadian prairie region may see a higher frequency of extreme droughts under projected global warming, potentially similar to the most arid periods seen during the mid-Holocene when many lake basins completely dried out.  相似文献