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31.
PHILIP HIRSCH 《The Geographical journal》2009,175(2):124-132
This paper explores the notion of frontiers as 'in-between' spaces that define particular transitions. Three contexts of frontier and their rapidly changing nature form the basis of the analysis. Agricultural frontiers (typically between farmland and forest) are defined by new relations of production and interplays between conservation, shifting modes of agriculture and natural resource use and management. Peri-urban frontiers (between countryside and city) are taken beyond their desakota/chaan-meuang locations to a more generic interplay between urbanity and rurality in defining livelihood and identity. National frontiers (between nation states with sharply different political and economic conditions) are transcended from above in the form of new regionalisms, and, from below, in migrations and other transboundary influences and flows. The paper proposes the frontier as both a spatial and temporal heuristic for understanding development and associated societal transitions in Thailand. 相似文献
32.
We present the results of retracking 18 cycles (15 from the Jason-TOPEX collinear period) of Jason-1 data. We used the retracking method of Rodriguez which simultaneously solves for all relevant waveform parameters using a 26 Gaussian model of the altimeter point target response. We find significant differences from the Jason-1 Project retracking in the key parameters of range and significant wave height (SWH) in the second version of the Project SGDRs. The differences from the Jason-1 data have a strong dependence on off-nadir angle and some dependence on SWH. The dependence of range on SWH is what is called sea state bias. The retracking technique also estimates surface skewness. For Jason-1 with its very clean waveforms we make the first direct estimates of the skewness effect on altimeter data. We believe that the differences found here and thus in overall sea surface height are the result of the standard project processing using a single Gaussian approximation to the Point Target Response (PTR) and not solving simultaneously for off nadir angle. We believe that the relatively large sea state bias errors estimated empirically for Jason-1 during the cal/val phase result from sensitivity of quantities, particularly SWH, in project GDRs to off nadir angle. The TOPEX-Jason-1 bias can be determined only when a full retracking of Jason-1 is done for the collinear period. 相似文献
33.
34.
ALEKSIS DREIMANIS PHILIP GIBBARD 《Boreas: An International Journal of Quaternary Research》2005,34(2):101-122
The Catfish Creek Drift Formation is a significant and extensive lithostratigraphical marker unit in SW Ontario. Here the stratotype, exposed in the Lake Erie bluffs of the Plum Point-Bradtville (Grandview) area south of London, Ontario, Canada, is proposed. It consists of subglacial and proglacial sediments deposited at the beginning of the Nissouri Phase of the Wisconsinan glaciation. In the 2.5-km-long stratotype section, the Catfish Creek Drift consists of 9 members. Five of them, the Dunwich and Grandview I-IV members, mainly consist of till, with minor components of stratified drift. The Dunwich till was deposited by the Huron-Georgian Bay lobe, but the Grandview I-IV tills by the Erie lobe. The Zettler Farm Member consists of co-lobal till in the central part of the section and of a proglacial waterlain flow diamicton and a subglacial undermelt diamicton in the SW part. Three members consist entirely of stratified drift; the glaciolacustrine silty and clayey Waite Farm Member, the ice-marginal deltaic Oosprink Farm Member and the Boy Scout Camp Member - deposited by meltwater streams in subglacial channels. The sequence of interbedded till and stratified drift represents the oscillating advance of the Laurentide Ice Sheet in the Lake Erie basin. 相似文献
35.
Sheet slides and rotational failures on a convergent margin: the Kidnappers Slide, New Zealand 总被引:1,自引:0,他引:1
The Kidnappers Slide, on the upper continental slope of the convergent margin off eastern North Island, New Zealand, has been re-examined using a grid of high-resolution seismic reflection profiles. The slide is not a single feature but a complex of sheet slides and rotational failures ranging from 20 to 140 m thick, and covering a total area of 720 km2. Failures occurred in several phases, on slopes of 1–5°, in late Quaternary, muddy, shelf-edge clinoforms that have prograded into an accretionary, trench-slope basin. Piston cores and seismic stratigraphy show that the main failure probably occurred in early Holocene times but that movements ranged from mid last glacial to late Holocene times. The sheet slides exhibit tensional collapse via numerous listric normal faults that sole out on glide planes; there is no clear evidence of compressional structures anywhere within the complex. The glide planes occur at progressively deeper stratigraphic levels towards the northeastern end of the complex, and near the steep slope that defines the seaward edge of the trench-slope basin. There is retrogressive failure at the top of the slope. The surficial slides are being deformed by growth of active tectonic faults and folds associated with the convergent plate margin. This type of slope failure may be partially related to metastable sandy layers within the last glacial age progradational sequence, and possibly to formation of bubble phase gas at shallow depths. Failure was probably triggered by earthquake loading of sediments in this highly seismic region. 相似文献
36.
The Gosse Pile mafic-ultramafic intrusion is a laycred igneousbody, the upper part of which was involved in localized ductiledeformation (low angle faulting) soon after crystallization.A complete gradation between rocks showing typically igneoustextures and layering and those showing typically tectonic,or metamorphic, textures and layering can be observed. Textures and preferred orientations in the undeformed part ofthe intrusion are very similar to those found in other layeredigneous bodies. Orthopyroxenes show very strong preferred orientationsin some parts of the body. The metamorphic textures and layering of the deformed rocksare identical to flow-layering which is used asan essential criterion for distinguishing alpine-typefrom stratiform bodies. The Gosse Pile Body thusdemonstrates that at least some of the alpine-typebodies may be produced byin situ deformation of stratiformbodies. 相似文献
37.
Water vapor transport in the NCAR CCM2 总被引:1,自引:0,他引:1
38.
GERALD K. MOORE 《水文科学杂志》2013,58(4):407-421
Abstract Remote sensing instruments obtain an optical measure of water colour and turbidity. Colour increases the absorption of light in water and decreases the remotely sensed signal; turbidity increases the backscatter of light. For low concentrations of suspended materials, spectral reflectance is determined mostly by the absorptance characteristics of water; for higher concentrations, the absorptance characteristics of suspended particles are the most important factor. Remote sensing offers considerable advantages for the study of large areas, determination of current and circulation patterns, and monitoring of sedimentation, water productivity, and eutrophication. 相似文献
39.
ANDREW J. RUSSELL PHILIP M. MARREN 《Boreas: An International Journal of Quaternary Research》1998,27(4):231-242
This study provides an insight into the impact of probably the largest flood ever to have been identified in mainland Britain by examining new sedimentary evidence from the Auchteraw terrace, Fort Augustus, Scotland. Study of three sections reveals a succession consisting of: (1) sheet gravels; (2) large trough-shaped depressions infilled with cross-stratified sands and gravels; (3) smaller-scale, finer-grained cross-strata; and (4) sheet-like, occasionally channelized, bimodal sand and gravel beds. This study shows that both the sedimentology and morphology of the Auchteraw terrace are consistent with jökulhlaup deposition and reveal a greater variety of lithofacies types than identified in previous studies of jökulhlaups from ice-dammed lakes. The fine-grained nature of the sediment discussed in this study emphasizes the importance of sediment supply for the formation of distinctive jökulhlaup successions. The sedimentary evidence recorded here provides a valuable tool for the interpretation of the magnitude and frequency of proglacial meltwater flows associated with Pleistocene ice sheets worldwide. 相似文献
40.
The Dry Valley Drilling Project (DVDP) cored three holes (DVDP1, 2 and 3) at Hut Point Peninsula (HPP) on Ross Island, Antarctica.DVDP 1 reached 201 m and penetrated 40 stratigraphic units,mainly basanite and Ne-hawaiite lava flows and associated pyroclasticrocks. DVDP 2 and 3 are nearly identical. DVDP 3 reached 381m and penetrated 15 stratigraphic units. The lower unit is a214 m thick basanite hyaloclastite, this is overlain by flowsand pyroclastic rocks of basanite, Ne-hawaiite, and then alternatingNe-mugearite and Ne-benmoreite flows. Phonolite stratigraphicallyoverlies the drill site. Primary olivine (Fo88-Fo74) is confined to the basanites, althoughxenocrysts occur in other rock types. Calcium-rich clinopyroxeneis ubiquitous but shows little variation in terms of Ca, Mg,Fe2+. Kaersutite is common in all lavas except the basanitesand shows very little compositional variation. It is believedto have crystallized at temperatures below 1100 °C and atpressures between 1·5 and 10 kb. Rhönite, a titanosilicateis a common groundmass phase in some basanite lavas. Oxide mineralsshow a wide range of compositions; spinel and chromian spineloccur as inclusions in olivine in the basanites. Titano-magnetiteoccurs in most samples examined. Labradorite is the predominantfeldspar in the basanite, with andesine and oligoclase importantin all other rock types. DVDP and HPP samples show a well-defined sequence of basanite-Ne-hawaiite-Ne-mugearite-Ne-benmoreite-phonolite,termed the DVDP lava lineage. Differentiation of the lineagehas been modeled using major element least squares mass balancemodels. Over 75 per cent of the evolution from basanite to phonoliteoccurs in the initial step from basanite to Ne-hawaiite, whichrepresents a 43 per cent residual. The phonolite is only a 25per cent residual from a basanite parent; thus even though Ne-mugeariteand Ne-benmoreite are common, they represent only minor stepsin the differentiation sequence. The mass balance models indicatethat olivine, clinopyroxene, kaersutite, opaque oxides and feldsparare the dominant fractionated phases. Trace element (includingrare earth element) contents calculated using the Rayleigh equationconfirm all models.
* Present address: Department of Geoscience, New Mexico Institute of Mining and Technology, Socorro, New Mexico 87801. 相似文献