Editorial     

Gary Huckleberry  Jamie Woodward 《Geoarchaeology》2008,23(1):1-2

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Short contribution: Nile flow failure at the end of the Old Kingdom,Egypt: Strontium isotopic and petrologic evidence     

Jean‐Daniel Stanley  Michael D. Krom  Robert A. Cliff  Jamie C. Woodward 《Geoarchaeology》2003,18(3):395-402

Strontium isotopic and petrologic information, obtained from sediment cores collected in the Nile delta of Egypt, indicate that paleoclimatic and Nile baseflow conditions changed considerably from about 4200 to 4000 cal yr B.P. in the Nile basin. Our study records a higher proportion of White Nile sediment transported during the annual floods at ca. 6100 cal yr B.P. than towards 4200 cal yr B.P., at which time suspended sediment from the Blue Nile formed a significantly larger fraction of the total load. This resulted from a decrease in vegetative cover and an increase in erosion rate accompanying the marked decline in rainfall. These new geoscience data indicate major changes in annual flooding and baseflow of the river Nile, marked short‐term paleoclimatic‐related events that may in part have led to the collapse of the Old Kingdom. © 2003 Wiley Periodicals, Inc.  相似文献   

Seismic fragilities of single-column highway bridges with rocking column-footing     

Yazhou Xie  Jian Zhang  Reginald DesRoches  Jamie E. Padgett 《地震工程与结构动力学》2019,48(7):843-864

Rocking isolation has been increasingly studied as a promising design concept to limit the earthquake damage of civil structures. Despite the difficulties and uncertainties of predicting the rocking response under individual earthquake excitations (due to negative rotational stiffness and complex impact energy loss), in a statistical sense, the seismic performance of rocking structures has been shown to be generally consistent with the experimental outcomes. To this end, this study assesses, in a probabilistic manner, the effectiveness of using rocking isolation as a retrofit strategy for single-column concrete box-girder highway bridges in California. Under earthquake excitation, the rocking bridge could experience multi-class responses (eg, full contacted or uplifting foundation) and multi-mode damage (eg, overturning, uplift impact, and column nonlinearity). A multi-step machine learning framework is developed to estimate the damage probability associated with each damage scenario. The framework consists of the dimensionally consistent generalized linear model for regression of seismic demand, the logistic regression for classification of distinct response classes, and the stepwise regression for feature selection of significant ground motion and structural parameters. Fragility curves are derived to predict the response class probabilities of rocking uplift and overturning, and the conditional damage probabilities such as column vibrational damage and rocking uplift impact damage. The fragility estimates of rocking bridges are compared with those for as-built bridges, indicating that rocking isolation is capable of reducing column damage potential. Additionally, there exists an optimal slenderness angle range that enables the studied bridges to experience much lower overturning tendencies and significantly reduced column damage probabilities at the same time.  相似文献   

Development of push moraines in deeply frozen sediment adjacent to a cold-based glacier in the McMurdo Dry Valleys,Antarctica     

Sean Fitzsimons  Jamie Howarth 《地球表面变化过程与地形》2020,45(3):622-637

Previous studies of push moraines have concluded that structural architecture is controlled by a combination of stress exerted by flowing ice and the rheology of the deforming sediment. However, the relationship between deformation processes and the thermal/hydrologic conditions within the sediment remains ambiguous. Using a combination of surface mapping, logging exposures and ground penetrating radar we examine the relationships between surface morphology, material properties and development of deformation structures in deeply frozen sediment that has been deformed by Joyce Glacier, a cold-based glacier in the McMurdo Dry Valleys. The structural architecture of the push moraines is characterized by a combination of brittle and ductile deformation structures that have produced a structurally complex pattern of thrust faults, low angle listric thrusts and recumbent folds that extend 400 m beyond the glacier margin. Deformation is ductile where the ice concentration exceeds c. 65% volume and predominantly brittle where the ice concentration is less than c. 65%. The change in rheology reflects transition in behaviour from the material having a predominantly frictional character when the ice is limited to pore spaces to a non-frictional character in which strength is primarily determined by the cohesive strength of the ice. This work shows that glaciotectonic deformation can occur in deeply frozen permafrost where there is no liquid pore water. We conclude that the presence of liquid porewater is not a necessary condition for the development of glaciotectonic deformation or for the formation of push moraines. © 2019 John Wiley & Sons, Ltd.  相似文献   

A clear and present danger: Ladakh's increasing vulnerability to flash floods and debris flows          下载免费PDF全文

Alan D. Ziegler  Sebastian I. Cantarero  Robert J. Wasson  Pradeep Srivastava  Sonam Spalzin  Winston T. L. Chow  Jamie Gillen 《水文研究》2016,30(22):4214-4223

This preliminary investigation of the recent spate of deadly flash floods and debris flows in Ladakh (India) over the last decade identifies uncontrolled development in hazardous locations as an important factor contributing to loss of life and property damage in this high mountain desert. The sediments exposed in the channel banks and on the alluvial fans of several mountain streams in the area indicate a long history of flash floods and debris flows resulting from intense storms, which appear to have increased in frequency within the last decade. The signposts of these recurrent hazards are being ignored as a growing economy, which is boosted by a well‐established tourism industry, is now driving development onto lands that are susceptible to floods and debris flow hazards. In this science briefing we argue that the increasing vulnerability in Ladakh should be addressed with sound disaster governance strategies that are proactive, rather than reactionary. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

The Precambrian–Cambrian nonconformity at the Ercall Quarries,The Wrekin,Shropshire, UK     

Jamie K. Pringle  Ian G. Stimpson 《Geology Today》2013,29(5):195-199

The Precambrian–Cambrian boundary is iconic, marking the first appearance of shelly fauna in the fossil record, and opening the Phanerozoic Eon. In England and Wales, the transition from predominantly Precambrian igneous rocks to Cambrian sedimentary strata is generally unconformable. An exceptional exposure of this transition can be observed in the Ercall Quarries in Shropshire, a classic locality in all senses of the word.  相似文献   

Depositional processes across the Sinú Accretionary Prism,offshore Colombia     

Jamie S. Vinnels  Robert W.H. Butler  William D. McCaffrey  Douglas A. Paton 《Marine and Petroleum Geology》2010,27(4):794-809

The Pliocene to Recent of the Sinú Accretionary Prism, offshore Colombia, features gravity current dominated basins characterised primarily by channel- and sheet-like architectures and those with dominantly hemipelagic fills. The prism is fed by rivers that drain from uplifted older basins and volcanic Andean terranes to the south and east which source large volumes of sediment to the Colombian Shelf into the Colombian Basin. Some basin fills show evidence of both localised fold-induced sediment failure and regional-scale shelf collapse, both related to the generation and destruction of oversteepened slopes. Large scale collapses can create new sediment routing pathways and/or local depocentres into which sediment subsequently accumulates. In the Colombian Basin, even relatively distal basins show evidence of channel activity related primarily to the creation of new sediment distribution pathways through breaches in the substrate barriers between basins. These channels are often orientated parallel to the regional drainage trend, suggesting that regional sediment transport trends can assert themselves relatively early in a basin filling history regardless of the local bathymetric grain. While, at a regional scale, sediment dispersal fairways reflect drainage from the continental shelf to the basin floor, intraslope basins form local bathymetric obstructions that can drive local spatial variations in sediment distribution. Thus, both local and regional length scales of bathymetric control are evident within the intraslope basins of the Sinú Accretionary Prism. Although regional dispersal patterns generally become more important in time, individual intraslope basins exhibit more complex filling histories because events such as sill or shelf collapse may serve to disrupt established distribution pathways, initiating repeated episodes of adjustment.  相似文献   

Pilgrims,progress, and the political economy of disaster preparedness – the example of the 2013 Uttarakhand flood and Kedarnath disaster          下载免费PDF全文

Alan D. Ziegler  Robert J. Wasson  Alok Bhardwaj  Y. P. Sundriyal  S. P. Sati  Navin Juyal  Vinod Nautiyal  Pradeep Srivastava  Jamie Gillen  Udisha Saklani 《水文研究》2014,28(24):5985-5990

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Compound‐specific carbon isotope compositions of aldehydes and ketones in the Murchison meteorite     

Danielle N. Simkus  Jos C. Aponte  Robert W. Hilts  Jamie E. Elsila  Christopher D. K. Herd 《Meteoritics & planetary science》2019,54(1):142-156

Compound‐specific carbon isotope analysis (δ¹³C) of meteoritic organic compounds can be used to elucidate the abiotic chemical reactions involved in their synthesis. The soluble organic content of the Murchison carbonaceous chondrite has been extensively investigated over the years, with a focus on the origins of amino acids and the potential role of Strecker‐cyanohydrin synthesis in the early solar system. Previous δ¹³C investigations have targeted α‐amino acid and α‐hydroxy acid Strecker products and reactant HCN; however, δ¹³C values for meteoritic aldehydes and ketones (Strecker precursors) have not yet been reported. As such, the distribution of aldehydes and ketones in the cosmos and their role in prebiotic reactions have not been fully investigated. Here, we have applied an optimized O‐(2,3,4,5,6‐pentafluorobenzyl)hydroxylamine (PFBHA) derivatization procedure to the extraction, identification, and δ¹³C analysis of carbonyl compounds in the Murchison meteorite. A suite of aldehydes and ketones, dominated by acetaldehyde, propionaldehyde, and acetone, were detected in the sample. δ¹³C values, ranging from ?10.0‰ to +66.4‰, were more ¹³C‐depleted than would be expected for aldehydes and ketones derived from the interstellar medium, based on interstellar ¹²C/¹³C ratios. These relatively ¹³C‐depleted values suggest that chemical processes taking place in asteroid parent bodies (e.g., oxidation of the IOM) may provide a secondary source of aldehydes and ketones in the solar system. Comparisons between δ¹³C compositions of meteoritic aldehydes and ketones and other organic compound classes were used to evaluate potential structural relationships and associated reactions, including Strecker synthesis and alteration‐driven chemical pathways.  相似文献   

Inter‐comparison of hydro‐climatic regimes across northern catchments: synchronicity,resistance and resilience     

Sean K. Carey  Doerthe Tetzlaff  Jan Seibert  Chris Soulsby  Jim Buttle  Hjalmar Laudon  Jeff McDonnell  Kevin McGuire  Daniel Caissie  Jamie Shanley  Mike Kennedy  Kevin Devito  John W. Pomeroy 《水文研究》2010,24(24):3591-3602

The higher mid‐latitudes of the Northern Hemisphere are particularly sensitive to climate change as small differences in temperature determine frozen ground status, precipitation phase, and the magnitude and timing of snow accumulation and melt. An international inter‐catchment comparison program, North‐Watch, seeks to improve our understanding of the sensitivity of northern catchments to climate change by examining their hydrological and biogeochemical responses. The catchments are located in Sweden (Krycklan), Scotland (Mharcaidh, Girnock and Strontian), the United States (Sleepers River, Hubbard Brook and HJ Andrews) and Canada (Catamaran, Dorset and Wolf Creek). This briefing presents the initial stage of the North‐Watch program, which focuses on how these catchments collect, store and release water and identify ‘types’ of hydro‐climatic catchment response. At most sites, a 10‐year data of daily precipitation, discharge and temperature were compiled and evaporation and storage were calculated. Inter‐annual and seasonal patterns of hydrological processes were assessed via normalized fluxes and standard flow metrics. At the annual‐scale, relations between temperature, precipitation and discharge were compared, highlighting the role of seasonality, wetness and snow/frozen ground. The seasonal pattern and synchronicity of fluxes at the monthly scale provided insight into system memory and the role of storage. We identified types of catchments that rapidly translate precipitation into runoff and others that more readily store water for delayed release. Synchronicity and variance of rainfall–runoff patterns were characterized by the coefficient of variation (cv) of monthly fluxes and correlation coefficients. Principal component analysis (PCA) revealed clustering among like catchments in terms of functioning, largely controlled by two components that (i) reflect temperature and precipitation gradients and the correlation of monthly precipitation and discharge and (ii) the seasonality of precipitation and storage. By advancing the ecological concepts of resistance and resilience for catchment functioning, results provided a conceptual framework for understanding susceptibility to hydrological change across northern catchments. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献