Climate risk management requires explicit representation of societal trade-offs   总被引：1，自引：0，他引：1  

Gregory Garner  Patrick Reed  Klaus Keller 《Climatic change》2016,134(4):713-723

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A new strategy for analyzing the chronometry of constructed rock features in deserts     

Niccole Villa Cerveny  Russell Kaldenberg  Judyth Reed  David S. Whitley  Joseph Simon  Ronald I. Dorn 《Geoarchaeology》2006,21(3):281-303

The western Great Basin contains thousands of constructed rock features, including rock rings, cairns, and alignments. Unlike subtractive geoglyphs, such as the Nasca Lines of Peru, that remove desert pavement, these surface features alter the location and positioning of cobble‐ to bouldersized rocks. The chronology of surface rock features has remained unconstrained by numerical ages because no prior chronometric approach has been able to yield age control. We propose a new strategy for studying these features by analyzing anthropogenic modifications to rock coatings, an approach that permits the use of several dating methods, two of which are assessed here: radiocarbon dating of pedogenic carbonate and rock‐varnish microlaminations. Initial results from Searles Valley, eastern California, suggest that constructed rock features may be as old as early Holocene and terminal Pleistocene. Archaeological surveys of desert areas would be greatly enhanced if they noted altered positions of rock coatings. © 2006 Wiley Periodicals, Inc.  相似文献   

Discovery of A New Class of Pulsating Stars: Gravity-mode Pulsators among Subdwarf B Stars     

Elizabeth M. Green  Keith Callerame  Ivo R. Seitenzahl  Brooke A. White  Elaina A. Hyde  Melissa Giovanni  Mike Reed  Gilles Fontaine  Roy Østensen 《Astrophysics and Space Science》2003,284(1):65-68

During the course of an ongoing CCD monitoring program to investigate low-level light variations in subdwarf B (sdB) stars, weserendipitously discovered a new class of multimode pulsators withperiods of the order of an hour. These periods are a factor of tenlonger than those of previously known multimode sdB pulsators (EC14026 stars), implying the new pulsations are due to gravity modes rather than pressure modes. The iron opacity instability that drives the short period EC 14026 stars is effective in hot sdB's. Thelong period pulsators are found only among cooler sdB stars, wherethey are surprisingly common. The mechanism responsible for excitingthe deeper g-modes in cool sdB's is currently unknown, but thetemperature and gravity range in which these stars occur must be animportant clue. We present the first observational results for thisnew class of pulsating sdB stars, and discuss some possible implications.  相似文献   

Resolving the pulsations of the subdwarf B star KPD 2109 + 4401     

A.-Y. Zhou  M. D. Reed  S. Harms  D. M. Terndrup  D. An  S. Zola  K. D. Gazeas  P. G. Niarchos  W. Ogloza  A. Baran  G. W. Wolf 《Monthly notices of the Royal Astronomical Society》2006,367(1):179-185

We present the results of extensive time-series photometry of the pulsating subdwarf B star KPD 2109 + 4401. Our data set consists of 29 data runs with a total length of 182.6 h over 31 d, collected at five observatories in 2004. These data comprised high signal-to-noise ratio observations acquired with larger telescopes and wider time-coverage observations obtained with smaller telescopes. They are sufficient to resolve the pulsation structure to 0.4 μHz and are the most extensive data set for this star to date. With these data, we identify eight pulsation frequencies extending from 4701 to 5481 μHz, corresponding to periods of 182–213 s. The pulsation frequencies and their amplitudes are examined over several time-scales with some frequencies showing amplitude variability.  相似文献   

Geochemistry and stratigraphic correlation of basalt lavas beneath the Idaho Chemical Processing Plant, Idaho National Engineering Laboratory     

M. F. Reed  R. C. Bartholomay  S. S. Hughes 《Environmental Geology》1997,30(1-2):108-118

 Thirty-nine samples of basaltic core were collected from wells 121 and 123, located approximately 1.8 km apart north and south of the Idaho Chemical Processing Plant at the Idaho National Engineering Laboratory. Samples were collected from depths ranging from 15 to 221 m below land surface for the purpose of establishing stratigraphic correlations between these two wells. Elemental analyses indicate that the basalts consist of three principal chemical types. Two of these types are each represented by a single basalt flow in each well. The third chemical type is represented by many basalt flows and includes a broad range of chemical compositions that is distinguished from the other two types. Basalt flows within the third type were identified by hierarchical K-cluster analysis of 14 representative elements: Fe, Ca, K, Na, Sc, Co, La, Ce, Sm, Eu, Yb, Hf, Ta, and Th. Cluster analyses indicate correlations of basalt flows between wells 121 and 123 at depths of approximately 38–40 m, 125–128 m, 131–137 m, 149–158 m, and 183–198 m. Probable correlations also are indicated for at least seven other depth intervals. Basalt flows in several depth intervals do not correlate on the basis of chemical compositions, thus reflecting possible flow margins in the sequence between the wells. Multi-element chemical data provide a useful method for determining stratigraphic correlations of basalt in the upper 1–2 km of the eastern Snake River Plain. Received: 16 February 1996 · Accepted: 1 April 1996  相似文献   

The cluster galaxy circular velocity function     

V. Desai  J. J. Dalcanton†  L. Mayer  D. Reed  T. Quinn  F. Governato‡ 《Monthly notices of the Royal Astronomical Society》2004,351(1):265-278

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Annual Primary Production in Narragansett Bay with no Bay-Wide Winter–Spring Phytoplankton Bloom     

C. Oviatt  A. Keller  L. Reed 《Estuarine, Coastal and Shelf Science》2002,54(6):1013

Primary production was estimated over the annual cycle from ¹⁴C incubations conducted in 5 m deep enclosures and modeled for 16 stations in Narragansett Bay with data from biweekly surveys in which light, chlorophyll, attenuation coefficients and other parameters were measured. Annual values ranged from 160 g C m⁻² y⁻¹ in the lower West Passage to 619 g C m⁻² y⁻¹ at the mouth of the Providence River. The annual bay-wide, area mean fell near the middle of this range at 323 g C m⁻² y⁻¹ and was not apparently different from previous surveys. In the 1998 warm, El Niño winter, no bay-wide winter–spring phytoplankton flowered. Bloom limitation was correlated with warm temperatures which may have stimulated grazing rates. The lack of a bloom did not change annual levels of primary production but this alteration in carbon flow may impact macrofauna in the benthic infauna community.  相似文献   

Porometric properties of siliciclastic marine sand: a comparison of traditional laboratory measurements with image analysis and effective medium modeling     

Reed  A.H. Briggs  K.B. Lavoie  D.L. 《Oceanic Engineering, IEEE Journal of》2002,27(3):581-592

During the 1999 sediment acoustics experiment (SAX99), porometric properties were measured and predicted for a well sorted, medium sand using standard laboratory geotechnical methods and image analysis of resin-impregnated sediments. Sediment porosity measured by laboratory water-weight-loss methods (0.372 /spl plusmn/ 0.0073 for mean /spl plusmn/1 standard deviation) is 0.026 lower than determined by microscopic image analysis of resin-impregnated sediments (0.398 /spl plusmn/ 0.029). Values of intrinsic permeability (m/sup 2/) determined from constant-head permeameter measurements (3.29 /spl times/ 10/sup -11/ /spl plusmn/ 0.60 /spl times/ 10/sup -11/) and by microscopic image analysis coupled with effective medium theory modeling (2.78 /spl times/ 10/sup -11/ /spl plusmn/ 1.01 /spl times/ 10/sup -11/) are nearly identical within measurement error. The mean value of tortuosity factor measured from images is 1.49 /spl plusmn/ 0.09, which is in agreement with tortuosity factor determined from electrical resistivity measurements. Slight heterogeneity and anisotropy are apparent in the top three centimeters of sediment as determined by image-based porometric property measurements. However, the overall similarity for both measured and predicted values of porosity and permeability among and within SAX99 sites indicates sediments are primarily homogeneous and isotropic and pore size distributions are fairly uniform. The results indicate that an effective medium theory technique and two-dimensional image analysis accurately predicts bulk permeability in resin-impregnated sands.  相似文献   

Composition and origin of rhyolite melt intersected by drilling in the Krafla geothermal field, Iceland     

R. A. Zierenberg  P. Schiffman  G. H. Barfod  C. E. Lesher  N. E. Marks  J. B. Lowenstern  A. K. Mortensen  E. C. Pope  D. K. Bird  M. H. Reed  G. Ó. Friðleifsson  W. A. Elders 《Contributions to Mineralogy and Petrology》2013,165(2):327-347

The Iceland Deep Drilling Project Well 1 was designed as a 4- to 5-km-deep exploration well with the goal of intercepting supercritical hydrothermal fluids in the Krafla geothermal field, Iceland. The well unexpectedly drilled into a high-silica (76.5 % SiO₂) rhyolite melt at approximately 2.1 km. Some of the melt vesiculated while extruding into the drill hole, but most of the recovered cuttings are quenched sparsely phyric, vesicle-poor glass. The phenocryst assemblage is comprised of titanomagnetite, plagioclase, augite, and pigeonite. Compositional zoning in plagioclase and exsolution lamellae in augite and pigeonite record changing crystallization conditions as the melt migrated to its present depth of emplacement. The in situ temperature of the melt is estimated to be between 850 and 920 °C based on two-pyroxene geothermometry and modeling of the crystallization sequence. Volatile content of the glass indicated partial degassing at an in situ pressure that is above hydrostatic (~16 MPa) and below lithostatic (~55 MPa). The major element and minor element composition of the melt are consistent with an origin by partial melting of hydrothermally altered basaltic crust at depth, similar to rhyolite erupted within the Krafla Caldera. Chondrite-normalized REE concentrations show strong light REE enrichment and relative flat patterns with negative Eu anomaly. Strontium isotope values (0.70328) are consistent with mantle-derived melt, but oxygen and hydrogen isotope values are depleted (3.1 and ?118 ‰, respectively) relative to mantle values. The hydrogen isotope values overlap those of hydrothermal epidote from rocks altered by the meteoric-water-recharged Krafla geothermal system. The rhyolite melt was emplaced into and has reacted with a felsic intrusive suite that has nearly identical composition. The felsite is composed of quartz, alkali feldspar, plagioclase, titanomagnetite, and augite. Emplacement of the rhyolite magma has resulted in partial melting of the felsite, accompanied locally by partial assimilation. The interstitial melt in the felsite has similar normalized SiO₂ content as the rhyolite melt but is distinguished by higher K₂O and lower CaO and plots near the minimum melt composition in the granite system. Augite in the partially melted felsite has re-equilibrated to more calcic metamorphic compositions. Rare quenched glass fragments containing glomeroporphyritic crystals derived from the felsite show textural evidence for resorption of alkali feldspar and quartz. The glass in these fragments is enriched in SiO₂ relative to the rhyolite melt or the interstitial felsite melt, consistent with the textural evidence for quartz dissolution. The quenching of these melts by drilling fluids at in situ conditions preserves details of the melt–wall rock interaction that would not be readily observed in rocks that had completely crystallized. However, these processes may be recognizable by a combination of textural analysis and in situ analytical techniques that document compositional heterogeneity due to partial melting and local assimilation.  相似文献   

The role of intrusions in the formation of Irish-type mineralisation     

Jim McCusker  Christopher Reed 《Mineralium Deposita》2013,48(6):687-695

The Stonepark Prospect is located in County Limerick, south-central Ireland. Multiple zones of Zn–Pb mineralisation have been identified at Stonepark and these are approximately 5 km west of the Pallas Green Prospect. At Stonepark, the sulphide bodies are hosted within the Waulsortian Limestone and closely resemble other Irish-type deposits. The mineralisation is composed of pyrite-marcasite, sphalerite and galena with gangue Fe-dolomite and calcite cements. A key difference at Stonepark is the presence of Chadian-aged volcanic rocks (Knockroe Volcanics) that intrude into and overlie the Waulsortian Limestone. Subsequent hydrothermal brecciation of the Waulsortian Limestone and Knockroe intrusions resulted in the formation of tabular polymict breccia bodies containing mixed carbonate and clasts of intrusive rocks. These have then been overprinted by massive sulphide mineralisation. Further syn-mineralisation brecciation has overprinted the earlier breccias. Drilling has demonstrated a spatial relationship between the volume of intrusive rocks (dykes and polymict breccias) and Zn–Pb mineralisation. This association suggests that the intrusive rocks provided a mechanism for the introduction of the mineralising fluids into the breccia bodies. This is significant as to date no large controlling fault has been identified, as is seen at other Irish-type deposits. Further work is required to understand the alteration process of the intrusive rocks and how this may relate to the mineralising process.  相似文献