Climate change in southern Illinois, USA, based on the age and δC of organic matter in cave sediments     

Samuel V. Panno  B. Brandon Curry  Hong Wang  Keith C. Hackley  Chao-Li Liu  Craig Lundstrom  Juanzuo Zhou 《Quaternary Research》2004,61(3):301-313

Matrix-supported diamicton and uniform to laminated, silty, fine-grained sediment deposited from about 42,500 to 27,600 cal yr B.P. under slackwater conditions nearly filled two caves in southwestern Illinois. At some point, most of the sediment was flushed from the caves and from about 22,700 to 4000 cal yr B.P., floods deposited a drape of sandy and silty sediment on remnant slackwater successions, cobbly alluvium, and bedrock (especially from 7700 to 4000 cal yr B.P.). Clay mineral analyses of the slackwater cave sediment reveal a provenance of chiefly Petersburg Silt, a smectite- and illite-rich proglacial lacustrine unit present in the overlying Illinois Episode glacial succession. Today, remnants of the ancient subterranean slackwater deposits nearly fill several secondary passages and, in at least two locations, cover a cobble-mantled strath terrace 1.3 to 1.5 m above active stream channels. Slumping and sinkhole formation appear to have been important mechanisms for deposition of the ancient subterranean deposits. Slumping of these surficial deposits and associated vegetation can occur along the flanks of sinkholes (in addition to sinkhole formation) and enter caves; however, the finer organics, some of them comminuted during transport into the caves, become part of the cave alluvium. This finer organic fraction is the modern analog of the humified organic matter disseminated in slackwater sediment dated in this investigation by radiocarbon methods. Twenty-four ¹⁴C ages on humified organic matter provide chronologic control. The δ¹³C values of the organic matter reflect the proportion of C₄-type to C₃-type vegetation growing in and around swallets and sinkholes at the time of redeposition. Drought-tolerant C₄-type vegetation was more prevalent relative to C₃-type vegetation from 42,500 to 31,200 cal yr B.P. compared to conditions from 28,800 cal yr B.P. to the present. The δ¹³C values are consistent with the results from other investigations of speleothems and organic matter from loessial paleosols.  相似文献   

Paraglacial Modification of Glacigenic Sediment     

Alastair M. Curry  & Colin K. Ballantyne 《Geografiska Annaler: Series A, Physical Geography》1999,81(3):409-419

The sedimentological characteristics of in situ and paraglacially reworked till are compared at recently deglaciated sites in Norway. Glacigenic deposits reworked by debris flows are shown to retain many of the characteristics of the parent sediments, and cannot readily be distinguished from in situ till in terms of fabric strength or type, clast imbrication, shape, angularity or texture, matrix granulometry or packing. Paraglacially re-worked sediments appear to differ from in situ tills only in terms of preferred clast orientation (down flow rather than downvalley) and their structural and lithofacies characteristics. These criteria are employed to differentiate paraglacial sediments from unre-worked tills exposed in valley-side sections. The stratigraphic relations between these indicate glacial reworking of earlier paraglacial sediments as well as paraglacial remobilisation of glacigenic deposits, indicating cyclic alternation of glacial and paraglacial sediment transport.  相似文献   

Paraglacial modification of slope form     

Alastair M. Curry 《地球表面变化过程与地形》1999,24(13):1213-1228

The morphological consequences of paraglacial modification of valley-side drift slopes are investigated at six sites in Norway. Here, paraglacial slope adjustment operates primarily through the development of gully systems, whereby glacigenic sediment is stripped from the upper drift slope and redeposited in debris cones downslope. This results in an overall lowering of average gradient by up to 4·5° along gully axes. In general, slope profile adjustment appears to be characterized by a convergence of slope profiles towards an ‘equilibrium form’ with an upper rectilinear slope gradient at 29°± 4° and a range of concavities of approximately 0·0 to 0·4. After initial rapid incision, further gully deepening is limited, but gullies become progressively wider as sidewall gradients decline to c. 25°, after which parallel retreat appears to predominate. The final form of mature paraglacial gully systems consists of an upper bedrock-floored source area, a mid-slope area of broad gullies whose sidewalls rest at stable, moderate gradients, and a lower slope zone where gullies discharge onto the surfaces of debris cones and fans. Some gullies appear to have attained this final form and have stabilized following exhaustion of readily entrainable sediment within decades of gully initiation. At most sites, paraglacial activity has transformed steep drift-mantled valley sides into gullied slopes where an average of c. 2–3 m of surface lowering has taken place. At the most active sites, these average amounts imply minimum erosion rates averaging c. 90 mm a⁻¹ since gully initiation, which highlights the extreme rapidity of paraglacial erosion of deglaciated drift-mantled slopes. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Application of a serial extended forecast experiment using the ECMWF model to interpret the predictive skill of tropical intraseasonal variability     

P. A. Agudelo  C. D. Hoyos  P. J. Webster  J. A. Curry 《Climate Dynamics》2009,32(6):855-872

The extended-range forecast skill of the ECMWF operational forecast model is evaluated during tropical intraseasonal oscillation (ISO) events in the Indo-West Pacific warm pool. The experiment consists of ensemble extended serial forecasts including winter and summer ISO cases. The forecasts are compared with the ERA-40 analyses. The analysis focuses on understanding the origin of forecast errors by studying the vertical structure of relevant dynamical and moist convective features associated with the ISO. The useful forecast time scale for circulation anomalies is in average 13 days during winter compared to 7–8 days during summer. The forecast skill is not stationary and presents evidence of a flow-dependent nature, with states of the coupled system corresponding to long-lived convective envelopes associated with the ISO for which the skill is always low regardless of the starting date of the forecast. The model is not able to forecast skillfully the generation of specific humidity anomalies and results indicate that the convective processes in the model are associated with the erosion of the ISO forecast skill in the model. Circulation-associated anomalies are forecast better than moist convective associated anomalies. The model tends to generate a more stable atmosphere, limiting the model’s capability to reproduce deep convective events, resulting in smaller humidity and circulation anomalies in the forecasts compared to those in ERA-40.  相似文献   

Learning with practitioners: climate change adaptation priorities in a Canadian community     

Ian M. Picketts  John Curry  Stephen J. Déry  Stewart J. Cohen 《Climatic change》2013,118(2):321-337

Adaptation is already a necessary response to climate change for northern communities. The City of Prince George, in British Columbia, Canada, has been adjusting to impacts for years and there is a high level of local awareness of climate change. The purpose of this study was to collaborate with City staff and other organizations to undertake action-oriented research with the goal of creating a local adaptation strategy. Steps taken toward this goal included: producing downscaled climate scenarios; facilitating a workshop with local practitioners to prioritize impacts; gathering public feedback regarding impacts; and triangulating sources of information to determine community adaptation priorities. Changes to forests and increased flooding are the top local adaptation priorities, and impacts related to transportation, severe weather and water supply are high priorities. Other impacts, such as health effects and agricultural changes, are also important but did not rank highly using a risk framework focused on negative physical effects. Local impacts, actions the City is undertaking to address them and suggestions for implementing adaptation measures are summarized. The process of creating an adaptation strategy has proven highly valuable in Prince George and has precipitated further engagement and action. Due to the low profile of adaptation and limited resources in many communities, researchers and practitioners must capitalize on opportunities to incorporate adaptation into existing plans and processes. Lessons from the Prince George experience can be applied to other communities as they strive to effectively adapt to climate change.  相似文献   

Probabilistic discrimination between large-scale environments of intensifying and decaying African Easterly Waves     

Paula A. Agudelo  Carlos D. Hoyos  Judith A. Curry  Peter J. Webster 《Climate Dynamics》2011,36(7-8):1379-1401

About 50?C60% of Atlantic tropical cyclones (TCs) including nearly 85% of intense hurricanes have their origins as African Easterly Waves (AEWs). However, predicting the likelihood of AEW intensification remains a difficult task. We have developed a Bayesian diagnostic methodology to understand genesis of North Atlantic TCs spawned by AEWs through the examination of the characteristics of the AEW itself together with the large-scale environment, resulting in a probabilistic discrimination between large-scale environments associated with intensifying and decaying AEWs. The methodology is based on a new objective and automatic AEW tracking scheme used for the period 1980 to 2001 based on spatio-temporally Fourier-filtered relative vorticity and meridional winds at different levels and outgoing long wave radiation. Using the AEW and Hurricane Best Track Files (HURDAT) data sets, probability density functions of environmental variables that discriminate between AEWs that decay, become TCs or become major hurricanes are determined. Results indicate that the initial amplitude of the AEWs is a major determinant for TC genesis, and that TC genesis risk increases when the wave enters an environment characterized by pre-existing large-scale convergence and moist convection. For the prediction of genesis, the most useful variables are column integrated heating, vertical velocity and specific humidity, and a combined form of divergence and vertical velocity and SST. It is also found that the state of the large-scale environment modulates the annual cycle and interannual variability of the AEW intensification efficiency.  相似文献   

In situ permeabilities of selected coastal marine sediments     

Bennett  R.H. Hulbert  M.H. Curry  C. Johnson  H.P. Hutnak  M. Curry  K.J. 《Oceanic Engineering, IEEE Journal of》2002,27(3):571-580

An in situ permeameter probe was deployed off Fort Walton Beach, Florida in shallow-water coastal sandy sediment. Stations were occupied in a 600 m /spl times/ 600 m area. Intrinsic permeability in sand at 17 stations varied from 0.3 to 6.1 /spl times/ 10/sup -11/ m/sup 2/ to subbottom depths of 50 cm. Permeability decreased with increasing subbottom depth and minimal compaction. The sediment is a well-sorted, medium quartz sand with a mean grain size of approximately 0.34-0.52 mm and with 5%-8% carbonate shells and shell fragments. The probe was tested in a slightly finer-grained sediment near the main study area and revealed permeabilities of 0.1-3.2 /spl times/ 10/sup -11/ m/sup 2/. The permeabilities measured are reasonable for the observed sandy and slightly finer-grained sediments.  相似文献   

Magmas,mineralization and sea-floor spreading     

J. B. Wright  Patricia Mc Curry 《International Journal of Earth Sciences》1973,62(1):116-125

Relationships between granite bodies and mineralization in Nigeria and southwest England are cited as examples to support the thesis that ore solutions associated with igneous bodies do not necessarily develop by magmatic crystallization processes, but may form as independent by-products of magma generation. Similar conclusions have been reached for the metal provinces of western North America (Noble, 1970). Some hydrothermal solutions develop by expulsion of connate brines, mobilized by the passage of hot magma through sediments. Others may develop at deeper levels.Long-lived geochemical culminations in the deep crust or upper mantle (Schuiling, 1967) provide a possible source of reactivated metalliferous emanations in both nonorogenic and orogenic environments. An additional source of metals for ore deposits associated with island arcs and continental margin tectonism and igneous activity, may be provided by the mechanism of sea-floor spreading.The bulk of ocean floor sediments is scraped off and acreted onto non-descending crustal plates at subduction zones²). However, if the lowermost layers of these sediments are sufficiently compacted, they may be carried down into the mantle on the descending oceanic plate.They contain considerable amounts of heavy metals, which could be remobilized to reappear as ore deposits in island arcs and mountain chains of Andean type.In this way, the major episode of late Mesozoic underflow of the northeastern Pacific floor beneath western North America may have been responsible for much of the contemporaneous mineralization of that region. If this view is correct, much of the rich mineralization in the Andes may have a similar origin.Differences in amount and composition of sea floor sediment consumed, could account for regional changes in metal provinces along the tectonic grain. Remobilization of metals at different depths along Benioff zones could explain regional changes across the tectonic grain.

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Zusammenfassung Beziehungen zwischen Granitkörpern und Mineralisation in Nigeria und Südwest-England werden als Beispiele angeführt, um die These zu stützen, daß Erzlösungen in Verbindung mit Magmatit-Körpern sich nicht notwendigerweise von magmatischen Kristallisationsprozessen ableiten, sondern sich als unabhängige Nebenprodukte bei der Magmenerzeugung bilden können.Ähnliche Schlußfolgerungen sind für die Erzprovinzen des westlichen Nordamerika gezogen worden (Noble, 1970). Einige hydrothermale Lösungen entwickeln sich durch Ausstoß von connaten Laugen, mobilisiert durch das Durchströmen heißer Magma durch Sedimente. Andere mögen sich in tieferem Niveau entwickeln.Langandauernde geochemische Kulminationen in der tiefen Erdkruste oder im oberen Mantel (Schuiling, 1967) schaffen eine mögliche Quelle von reaktivierten, metallhaltigen Emanationen sowohl unter nichtorogenen als auch unter orogenen Bedingungen. Eine zusätzliche Quelle von Metallen für Erzlagerstätten, die an Inselbögen und Kontinentalrand-Tektonik sowie magmatische Aktivität gebunden sind, mag durch den Mechanismus des Sea Floor Spreading hervorgerufen werden.Die Masse der Ozeanboden-Sedimente wird abgetragen und auf nicht absteigenden Krusten-Plateaus tieferer Zonen angehäuft¹). Wenn jedoch die untersten Schichten ausreichend verdichtet sind, können sie in den Erdmantel auf dem sinkenden Ozean-Plateau hinabgelangen. Sie enthalten beträchtliche Mengen von Schwermetallen, die als Erzlagerstätten remobilisiert in Inselbögen und Gebirgsketten vom Anden-Typus wieder in Erscheinung treten können.Auf diese Weise mag die größere Episode der spät-mesozoischen Unterströmung des nordöstlichen Pazifikbodens unter das westliche Nordamerika für den Hauptanteil der gleichzeitigen Mineralisation dieser Region verantwortlich gewesen sein. Falls dieser Gesichtspunkt richtig ist, mögen viele der reichen Mineralisationen in den Anden einen ähnlichen Ursprung haben.Unterschiede in Menge und Zusammensetzung des aufgezehrten Maaresbodensediments könnten als regionale Veränderungen in Metallprovinzen entlang der tektonischen Struktur gedeutet werden. Remobilisierung von Metallen in verschiedenen Tiefen entlang der Benioff-Zonen könnten regionale Veränderungen quer zur tektonischen Richtung erklären.

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Résumé Les auteurs prennent comme exemple les rapports existant entre les corps granitiques et la minéralisation en Nigérie et dans le sud-ouest de l'Angleterre pour soutenir la thèse que les solutions minéralisantes associées avec les corps magmatiques, ne se développent pas nécessairement à partir de processus de cristallisation magmatiques, mais peuvent se former comme sous-produits indépendants de la génération du magma. Semblables conclusions ont été tirées pour les provinces métalliques de l'ouest de l'Amérique du Nord (Noble, 1970). Quelques solutions hydrothermales se développent par l'expulsion de saumures connées, mobilisées par le passage du magma chaud à travers des sédiments. D'autres peuvent se développer à des niveaux plus profonds.Des culminations géochimiques de longue durée dans la croûte terrestre ou dans le manteau supérieur (Schuiling, 1967) fournissent une source possible d'émanations métallifères réactivées, dans des conditions aussi bien non-orogéniques qu'orogéniques. Une source additionelle de métaux pour les gisements qui, comme l'activité magmatique, sont associés avec les guirlandes d'îles et avec la tectonique propre à la bordure continentale, peut être fournie par le mécanisme de l'expansion du fond des mers.La masse des sédiments du fond océanique est érodée et accumulée sur des plateaux crustaux, non en voie d'affaissements de zones plus profondes³).Quand cependant les couches plus inférieures de ces sédements sont suffisamment compactées, elles peuvent être entraînées dans le manteau sur le plateau océanique en voie d'affaissement.Elles contiennent des quantités considéreables de métaux lourds qui, remobilisés sous la forme de gisements de minerais, peuvent apparaître dans les guirlandes d'îles et les chaînes de montagnes de type andin.De cette façon, l'épisode majeur de la subduction, survenue au Mésozoïque supérieur, du fond du Pacifique NE sous l'ouest de l'Amérique du Nord peut avoir été responsable de la majeure partie de la minéralisation de cette région. Si cette opinion est juste, beaucoup de riches minéralisations rencontrées dans les Andes pourraient avoir une origine similaire.Des différences dans la quantité et la composition du sédiment océanique absorbé pourraient expliquer les changements régionaux dans les provinces métalliques tout le long de la structure tectonique. La remobilisation des métaux à des profondeurs différentes le long des zones Benioff pourrait expliquer les changements régionaux survenant transversalement à la direction tectonique.

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Cashing Out,Cashing In: Rural change on the south coast of Western Australia   总被引：1，自引：0，他引：1  

George N. Curry  Gina Koczberski  John Selwood 《The Australian geographer》2001,32(1):109-124

Over the past century the cultural and physical landscape of the Shire of Denmark on the south coast of Western Australia has been transformed by successive waves of in-migrants. The paper examines the period since the early 1970s when alternative lifestylers and early retirees, attracted by the district's natural beauty and low land prices, began moving in and acquiring former Group Settlement holdings. The activities of these and subsequent 'alternatives' and 'cashed out' early retirees settling in the district have raised the marketability of the Shire's cultural capital. These changes have occurred in association with broader processes of rural restructuring and changing notions of 'rurality'. Increasingly, Denmark's cultural and physical landscape has become a highly marketable product for consumption by Perth's affluent middle classes. In recent years land prices have risen rapidly as speculators and financiers seek to 'cash in' on the 'cashed out' society. The paper explores these issues and relates them to broader processes of economic and social change occurring at the national and international levels.  相似文献   

Field meeting at Barton,Hants: Saturday, 26th June, 1937     

E. St. John BurtonDennis Curry  M.A.  F.G.S. 《Proceedings of the Geologists' Association. Geologists' Association》1937,48(4):374-378

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