Consequences of short‐term changes in coastal processes: a case study     

M. R. Phillips 《地球表面变化过程与地形》2008,33(13):2094-2107

In 1997–98, unique critical beach erosion led to structural failure along the Penarth, South Wales, UK coastline and anthropogenic activities, such as the construction of the Cardiff Bay Barrage and offshore marine aggregate dredging, were suggested as causes. The time‐frame of significant erosion was between 1995 and 1997 and forcing agents (extreme sea level and wind direction) and shoreline indicators (mean beach level and MHW) were analysed in order to assess change. Water level analysis showed that although there was no significant difference between actual and predicted mean sea levels, extreme sea levels at that time were significantly higher (t = 3·305; d.f. = 8; p < 0·05). Three wind direction analyses (annual mean, mean annual maximum gust and mean annual maximum gust ≥28 kn) between 1995 and 1997 also showed significant differences (p < 0·05). All comprised more easterly components which meant they approached the beach from the sea. Furthermore, gusts ≥28 kn from the northeast quadrant, that is, 0° to 90° true, were significantly more frequent during these years (t = 3·674; d.f. = 8; p < 0·01). Justification of statistical significances was established and there was supporting evidence of unusual meteorological conditions at that time. Relationships showed correlation between forcing agents (extreme sea level and wind direction) and shoreline indicators (mean beach level and Mean High Water). Furthermore, regression analysis showed winds from the northeast quadrant resulted in steeper longshore gradients, as a consequence of beach material loss. Therefore, it was concluded that the critical erosion of Penarth beach between 1995 and 1997 was caused by increased wave attack from the northeast and southeast quadrants, generated by unique significant changes in wind direction and extreme sea levels. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Data reporting norms for 40Ar/39Ar geochronology     

Paul R. Renne  Alan L. Deino  Willis E. Hames  Matthew T. Heizler  Sidney R. Hemming  Kip V. Hodges  Anthony A.P. Koppers  Darren F. Mark  Leah E. Morgan  David Phillips  Brad S. Singer  Brent D. Turrin  Igor M. Villa  Mike Villeneuve  Jan R. Wijbrans 《Quaternary Geochronology》2009,4(5):346-352

Data reported in ⁴⁰Ar/³⁹Ar geochronology studies are commonly insufficient to allow computation of ages. This deficiency renders it difficult to compare ages based on different standards or constants, and often hinders critical evaluation of the results. Herein are presented an enumeration of the data that should be reported in all ⁴⁰Ar/³⁹Ar studies, including a discussion in support of these requirements. The minimum required data are identified and distinguished from parameters that are useful but may be derived from them by calculation. Finally, recommendations are made for metadata needed to document age calculations (e.g., from age spectrum or isochron analyses).  相似文献   

A time-space model for the distribution of shoreline archaeological sites in the lake superior basin     

Brian A. M. Phillips 《Geoarchaeology》1993,8(2):87-107

Archaeological site interpretation can be enhanced by consideration of related geological and geomorphological processes. Lake Superior has a history of glaciation, isostatic recovery, and water-level change. Two examples are given of shoreline sites at which interpretation is enhanced by an understanding of local geologic factors. The archaeologic history of the Lake Superior basin is reviewed, and three cultural traditions are recognized; (1) Paleoindian, (2) Archaic, and (3) Woodland. Three significant factors of geologic history are then discussed: (1) ice margin oscillation, (2) differential isostatic uplift, and (3) lake-level fluctuations. The factors reducing or improving shoreline archaeological site preservation are examined, and a summary model of shoreline site distribution for the Lake Superior basin is offered. It is concluded that the north shore provides the best potential for a complete archaeological record. © 1993 John Wiley & Sons, Inc.  相似文献   

Interpretation of migrated seismic reflection profiles across the northern Appalachians in Maine     

J. D. Unger  D. B. Stewart  J. D. Phillips 《Geophysical Journal International》1987,89(1):171-176

Summary. A simple line-migration technique has been developed and applied to deep crustal reflection data collected in the northern Appalachians of Quebec and central Maine. Preliminary interpretation of these data, combined with the results of gravity and refraction studies, shows thinning of the crust in two distinct steps beneath the Silurian-Devonian Merrimack synclinorium and shows evidence for Mesozoic crustal stretching and dike intrusion.  相似文献   

Erratum: The distances of less-evolved planetary nebulae: a further test of statistical distance scales     

J. P. Phillips 《Monthly notices of the Royal Astronomical Society》2005,363(4):1424-1424

  相似文献   

EVOLUTIONARY CHARACTERISTICS OF LAKES AND PALAEOCLIMATIC UNDULATION IN THE Q AID AM BASIN,CHINA     

黄麒  Teh-Lung Ku  Fred M.Phillips 《中国海洋湖沼学报》1993,11(1):34-45

The Qaidam Basin is. a tectonically controlled depression at 2700 m altitude on the northern margin of the Tibet Plateau. A succession of Neogene clastic sediments indicates lake depocentre migration from NW to SE. Towards late Pliocene, evaporative conditions developed with formation of gypsum, halite, celestite, mirabilite and bloedite. Continued deformation through Pleistocene developed a series of NW- SE trending domes and troughs. This setting continued to exert a controlling influence on basin and brine evolution and the progressive development of sulfate to chloride brines as, dry conditions intensified in late Pleistocene, at the end of which, extensive flat floors were formed in Dalangtan, Qarhan and other playas.The, model, which was set up based on the synthetic analyses, divides the fluctuating palaeoclimate since 750ka,B. P. into 11 warm and humid stages and 10 dry and cold stages. The water of the lakes evaporated during the dry-cold periods and were freshened during the warm-humid periods  相似文献   

Subsurface radar sounding of the martian polar cap: radiative transfer approach     

Ya.A. Ilyushin  R. Seu  R.J. Phillips 《Planetary and Space Science》2005,53(14-15):1427-1436

The problem of subsurface radar sounding of the martian polar caps [Ilyushin, 2004. Martian northern polar cap: layering and possible implications for radar sounding. Planet. Space Sci. 52, 1195–1207] is considered from the point of view of incoherent radiative transfer theory. Since it has been previously shown that the radar signal field within the polar cap has diffuse structure, there is a need for a statistical approach to the problem. Radiative transfer theory, which is now well developed, seems to be the most appropriate formalism for this approach.Several physical models of polar caps have been formulated. The asymptotic solutions for all proposed models are derived here. In the present paper only the case of orbital ground penetrating radar is considered, because it is of great interest in relationship to currently developed radar experiments. In principle, the approach is believed to be applicable to a wide class of short pulse and compressed chirp radar experiments, including both orbital and landed instruments and media more complicated than a simple plane parallel geometry. This work, however, is postponed to future papers.Techniques for retrieval of physical properties of polar caps from the radar measurements are proposed. From the observational data, the macroscopic parameters of the medium appearing in radiative transfer theory, i.e. the single scattering albedo and volume extinction coefficient can be estimated. These estimates put certain constraints on the physical parameters of the medium model introduced in the paper. With some additional information, known a priori or from other observations, these estimates can be used to retrieve physically meaningful information, for example, the average content of impurities in the ice.  相似文献   

Influences of the unsaturated,saturated, and riparian zones on the transport of nitrate near the Merced River,California, USA   总被引：1，自引：0，他引：1  

Joseph L. Domagalski  Steven P. Phillips  E. Randall Bayless  Celia Zamora  Carol Kendall  Richard A. WildmanJr  Janet G. Hering 《Hydrogeology Journal》2008,16(4):675-690

Transport and transformation of nitrate was evaluated along a 1-km groundwater transect from an almond orchard to the Merced River, California, USA, within an irrigated agricultural setting. As indicated by measurements of pore-water nitrate and modeling using the root zone water quality model, about 63% of the applied nitrogen was transported through a 6.5-m unsaturated zone. Transport times from recharge locations to the edge of a riparian zone ranged from approximately 6 months to greater than 100 years. This allowed for partial denitrification in horizons having mildly reducing conditions, and essentially no denitrification in horizons with oxidizing conditions. Transport times across a 50–100-m-wide riparian zone of less than a year to over 6 years and more strongly reducing conditions resulted in greater rates of denitrification. Isotopic measurements and concentrations of excess N₂ in water were indicative of denitrification with the highest rates below the Merced River. Discharge of water and nitrate into the river was dependent on gradients driven by irrigation or river stage. The results suggest that the assimilative capacity for nitrate of the groundwater system, and particularly the riverbed, is limiting the nitrate load to the Merced River in the study area.  相似文献   

Revealing Materials: plastics in alternative food economies     

Catherine Phillips 《The Australian geographer》2017,48(2):169-184

This article draws upon recent geographical work on assemblage to reconsider how we understand alternative food economies. In particular it brings attention to the devices upon which these economies rely—specifically plastics. Since the mid-twentieth century, plastics have developed close and complex relations with our agrifood systems; they facilitate commodity valuation and product circulation worldwide but are also recognised as problematic due to their environmental and human health impacts. Despite this paradox and the attention plastics increasingly receive, we know little of their relations with alternative food initiatives (AFIs). How do plastics inhabit alternative food economies? What associations and circulations become performed? What do these markets look like from a device-oriented perspective? To address these questions, the paper draws on fieldwork undertaken in Brisbane (Australia) with two AFIs—a weekly organic market and an online box program/wholesaler. Using visualisation and an assemblage approach discloses the presences, flows, functions, and tensions of plastics in AFIs. In this way, plastics are revealed but also act to reveal alternative food economies. This analysis steps away from evaluations of AFIs’ (in)effective challenge to neoliberalisation to consider them as complex, processual, sometimes ambivalent efforts that not only distribute ‘good food’ but engage in important ways with things like plastics.  相似文献   

Reconstructing nutrient histories in the Norfolk Broads, UK: implications for the role of diatom-total phosphorus transfer functions in shallow lake management   总被引：3，自引：0，他引：3  

Helen Bennion  Peter G. Appleby  Geoff L. Phillips 《Journal of Paleolimnology》2001,26(2):181-204

The fossil diatom records preserved in radiometrically dated sediment cores from four shallow lakes in the Norfolk Broads, UK (Barton Broad, Rollesby Broad, Wroxham Broad and Upton Broad) were analysed. A weighted-averaging partial least squares (WA-PLS) diatom-total phosphorus (TP) transfer function, based on a training set of 152 mostly shallow (maximum depth < 3 m) lakes in northwest Europe, was applied to the full diatom dataset for each core to reconstruct the past TP concentrations of the lakes. Owing to the dominance of non-planktonic Staurosira, Pseudostaurosira and Staurosirella spp. (formerly classified in the genus Fragilaria) throughout the diatom records, the quantitative diatom inferred TP (DI-TP) concentrations did not adequately reflect the changes that occurred in the lakes as indicated by shifts in the other diatom taxa, or as reported in the literature. This was most apparent at Barton Broad and Rollesby Broad, where there was a marked increase in the importance of planktonic taxa associated with highly nutrient-rich waters but no increase in DI-TP. The modern and fossil data were thus square-root transformed to downweight the dominant taxa and the new transfer function was applied to the cores. An improvement was seen only in the reconstruction for Barton Broad. Finally, the Staurosira, Pseudostaurosira and Staurosirella spp. were removed from the modern and fossil diatom data, and the transfer function was re-applied. The trends in DI-TP became less clear, particularly for Upton Broad and Barton Broad, owing to a paucity of data for calibration once these taxa were deleted from the counts data. The problems associated with reconstructing trophic status and determining TP targets for restoration from fossil diatom assemblages in these systems are discussed.  相似文献