Identification of buried sinkholes using refraction tomography at Ft. Campbell Army Airfield,Kentucky     

I. Camilo Higuera-Díaz  Philip J. Carpenter  Michael D. Thompson 《Environmental Geology》2007,53(4):805-812

Karst aquifers are highly susceptible to contamination, with numerous points of entry for contaminants through recharge features such as sinkholes, swallow holes and solutionally enlarged fractures. These recharge features may be filled or obscured at the surface, requiring the use of geophysical or remote sensing techniques for their identification. This study uses seismic refraction data collected at the Ft. Campbell Army Airfield (CAAF), Kentucky, USA, to test the hypothesis that refraction tomography is a useful tool for imaging bedrock depressions beneath thick overburden (greater than 20 m of unconsolidated sediment). Southeast of the main taxiway of CAAF seismic velocity tomograms imaged a bedrock low, possibly a closed depression, at a depth of 25 m that had been earlier identified through delay-time analysis of the same refraction data. Tomography suggests the bedrock low is about 250-m wide by 10-m deep at its widest point. High rates of contaminant vapor extraction over the western extension of this feature suggest a high concentration of contaminants above, and within, this filled bedrock low, the base of which may contain solutionally enlarged fractures (i.e. karst conduits) that could funnel these contaminants to the upper or lower bedrock aquifers. This study thus demonstrates the viability of seismic refraction tomography as a tool for identification of filled sinkholes and bedrock depressions in karst areas.  相似文献   

Laboratory simulation of the salt weathering of schist: II. Fragmentation of fine schist particles     

Tony Wells  Garry Willgoose  Philip Binning 《地球表面变化过程与地形》2007,32(5):687-697

Recent developments in long term landform evolution modelling have created a new demand for quantitative salt weathering data, and in particular data describing the size distribution of the weathered rock fragments. To enable future development of rock breakdown models for use in landscape evolution and soil production models, laboratory work was undertaken to extend existing schist/salt weathering fragmentation studies to include an examination of the breakdown of sub‐millimetre quartz chlorite schist particles in a seasonally wet tropical climate. Laser particle sizing was used to assess the impact of different experimental procedures on the resulting particle size distribution. The results reveal that salt weathering under a range of realistic simulated tropical wet season conditions produces a significant degree of schist particle breakdown. The fragmentation of the schist is characterized by splitting of the larger fragments into mid‐sized product with finer material produced, possibly from the breakdown of mid‐sized fragments when weathering is more advanced. Salinity, the salt addition method and temperature were all found to affect weathering rates. Subtle differences in mineralogy also produce variations in weathering patterns and rates. It is also shown that an increase in drying temperature leads to accelerated weathering rates, however, the geometry of the fracture process is not significantly affected. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Globalisation, Regionalisation and Local Voices: The Asian Development Bank and Rescaled Politics of Environment in the Mekong Region   总被引：1，自引：0，他引：1  

Philip Hirsch 《Singapore journal of tropical geography》2001,22(3):237-251

Globalisation is manifested in the Mekong Region both through processes and discourses that reflect the ideology of a borderless world allowing easy passage of capital and commodities, and through resistance to such processes in an increasingly transnationalised civil society movement. However, more immediately significant supranational integrative agendas take the form of regionalisation, a process that has received less attention but which raises analogous concerns of re-scaled governance. The Asian Development Bank (ADB) has been a catalysing force for regionalisation amidst a host of regional processes and initiatives; as such it has found itself the object of critique as an institution and through the specific projects it has supported that have impacted on local communities and ecosystems. Meanwhile, local and NGO voices associated with the emergence of a vibrant civil society in Thailand and nascent civil society responses in neighbouring countries have challenged claims on resources made in the name of national development and regional integration.
This paper considers some key issues of re-scaling resource and environmental politics in the Mekong Region, and the extent to which challenges have been recast from national to regional development agendas. Politics of environment are shown to exist as a general rather than exceptional response to the region's development direction, and it is suggested that equitable and sustainable development increasingly needs to address simultaneously the re-scaling and reconfigurations of power in both environmental politics and the "infrapolitics" of environment. The paper is illustrated with case studies of dams in Laos and Thailand.  相似文献   

Application of short-wave infrared spectroscopy to define alteration zones associated with the Elura zinc–lead–silver deposit, NSW, Australia     

Yanyan Sun  Philip K. Seccombe  Kai Yang   《Journal of Geochemical Exploration》2001,73(1):63

Short-wave infrared reflectance spectra obtained from a Portable Infrared Mineral Analyser (PIMA) have been used to define alteration zones adjacent to base metal sulfide ore bodies at the Elura Mine, Cobar, Australia. The spectroscopic work identified white mica (sericite), chlorite and carbonates of hydrothermal origin in the alteration zones associated with the ore bodies. Weathering, alteration and ore zones can be discriminated by variations in the intensity and wavelength of relevant absorption features. Hydrothermal alteration is classified into four principal types, namely sericitic, silicic, chloritic and carbonate alteration. The first three types comprise overprinting hydrothermal assemblages of quartz, sericite, chlorite, ankerite, siderite, calcite and sulfides developed in strongly altered metasiltstone and slate of Early Devonian age, adjacent to the zinc–lead–silver mineralisation. An extensive zone of carbonate alteration, manifested as porphyroblasts of siderite in the host metasediments, is recognised beyond the zones of strong alteration. Spectral analysis is consistent with the mineralogical data obtained from XRD and XRF analyses and defines the limits of the alteration zones to distances of about 80 m around the ore bodies. The study demonstrates the potential for spectral analysis to assist with drill hole logging and the identification of alteration zones as part of mineral exploration and development programs.  相似文献   

Differential diatom dissolution in Late Quaternary sediments from Lake Manyara,Tanzania: an experimental approach   总被引：3，自引：0，他引：3  

Philip Barker 《Journal of Paleolimnology》1992,7(3):235-251

Diatom dissolution in saline lakes represents an important obstacle to the quantitative reconstruction of water chemistry and climate from lake sediment archives. This problem is here approached experimentally by artificially dissolving diatom-bearing core sediment from Lake Manyara, Tanzania. Manyara holds one of the longest continuous palaeolimnological records from tropical Africa although its interpretation is based on a fragmentary diatom record due to frustule dissolution. These experiments have revealed clear changes in assemblage composition as dissolution operated differentially with respect to diatom taxa. Differential dissolution has considerable impact on the water chemistry estimates derived from transfer functions. Taphonomy, rather than environmental change, may have been responsible for minor fluctuations in the diatom assemblages from Manyara, although major palaeohydrological changes during the Late Pleistocene and Early Holocene can be identified. Particularly well represented by MANE-87 is a period of intermediate lake level between 27 500 and 23 000 ¹⁴C yr BP which has regional palaeohydrological significance.  相似文献   

The Armenian earthquake of 1988 December 7: faulting and folding, neotectonics and palaeoseismicity   总被引：2，自引：0，他引：2  

H. Philip  E. Rogozhin  A. Cisternas  J. C. Bousquet  B. Borisov  A. Karakhanian 《Geophysical Journal International》1992,110(1):141-158

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Book reviews     

Mark S. T. Bukowinski  Philip E. Wannamaker  Manfred Koch  Yukio Fujinawa  Dr. Pradeep Talwani  D. Möhlmann  Andrew H. Knoll  Lucia Lovison-Golob  Krzysztof Haman  Hanna Pawłowska  Henryk Piwkowski  Dr. Anthony Dore  Nguyen Xuan Huy  Edward R. Cook  Jan Błecki  Jacek Leliwa-Kopystynski  Magdalena Sroczynska-Kozuchowska 《Pure and Applied Geophysics》1993,140(1):139-177

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Gravity anomalies and crustal shortening in the eastern Mediterranean   总被引：1，自引：0，他引：1  

Philip D. Rabinowitz  William B. F. Ryan 《Tectonophysics》1970,10(5-6):585-608

Crustal shortening of the ocean floor in the eastern Mediterranean is recognized by a marked thickening of the sedimentary layer seaward of the Hellenic and Calabrian island arcs. Steep gradients and large negative free-air anomalies in the gravity field along with a highly uniform, low regional heat flow are manifestations of the thickened crust. Bodies of recently deformed sediment in and seaward of the Hellenic Trough reveal the style, polarity, and dynamics of the thickening mechanism.

A linear buried anticlinal structure, inferred from analysis of surface ship gravity profiles, may mark the site of contemporary intrabasinal underthrusting. The distribution of earthquakes beneath the Mediterranean Ridge supports the interpretation that the Anaximander, Ptolomy, and Strabo Mountains are features comparable to large basement nappes. Cyprus is one such structure, offset to the south, where the oceanic crust and part of the upper mantle have been involved in the décollement.  相似文献   

Rare earths and other trace elements in Luna 16 soil     

Philip A. HelmkeLarry A. Haskin 《Earth and Planetary Science Letters》1972

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The production rate of Al from target elements in the Bruderheim chondrite     

Philip J Cressy Jr. 《Geochimica et cosmochimica acta》1971

An 840-g specimen of the Bruderheim chondrite was subjected to magnetic and heavy-liquid mineral separation procedures, resulting in a number of chemically distinct samples. These samples were analyzed for cosmogenic Al²⁶ by non-destructive gamma-gamma coincidence counting. The observed Al²⁶ specific activities were correlated with the chemical composition of potential target elements by a weighted least-squares fitting technique. The calculated Al²⁶ production rates, in dpm per kilogram of target element, are: Al, 1130 ± 190; Si, 245 ± 31; S, 133 ± 11; Mg, 28 ± 30. Production rates from Ca and Ni + Fe were estimated to be 24 and 2.2 dpm/kg, respectively, from spallation systematics.  相似文献