Field expressions of the transformation of debris flows into turbidity currents, with examples from the Polish Carpathians and the French Maritime Alps   总被引：1，自引：0，他引：1  

M. Felix  S. Leszczy&#x;ski  A. l&#x;czka  A. Uchman  L. Amy  J. Peakall 《Marine and Petroleum Geology》2009,26(10):2011-2020

Various transformation mechanisms can generate turbidity currents from subaqueous debris flows. Different transformation mechanisms have been described and interpreted in the past from laboratory experiments and from deposits, but the two approaches have not generally been linked. This has made the genetic interpretation and comparison of deposits difficult. In this paper a generic classification scheme of debrite–turbidite couplets is proposed based on transformation mechanisms inferred from laboratory experiments. Five different flow types (called A–E herein) and their resulting deposits are detailed, but they are all part of a continuous spectrum, and a mixture of types is likely to be found in the field. Type A flows are strong, dense debris flows that undergo little transformation. Their deposit will be a debrite overlain by a thin turbidite, which is separated from it by a clear grain size break. Type B flows are weaker and can develop waves at the debris flow-turbidity current interface. The deposit will be a debrite with a wavy top overlain by a turbidite that is thicker than for type A flows. For type C flows, the interfacial waves will grow so much that the debris flow disintegrates into separate parts. The deposit will consist of debrite lenses encased in a turbidite. Type D flows will undergo even more mixing than type C flows so that the debrite parts will be mixed. Their deposit will be a turbidite with laterally varying areas of debrite characteristics near the bed. Type E flows will be so transformed that the debris flow character has disappeared and the flow is a turbidity current with high sediment concentration. The deposit will be largely turbiditic. The flow types and deposits will be illustrated with some examples from two field areas: the Polish Carpathians and the French Maritime Alps.  相似文献   

Does fire alter soil water repellency in subtropical coastal sandy environments?          下载免费PDF全文

Amy M. White  David A. Lockington  Badin Gibbes 《水文研究》2017,31(2):341-348

Irregular wetting, water repellency, and preferential flow are well‐documented properties of coastal sandy podzols, though little is known about the effect of fire on unsaturated zone processes in this environment. This study investigates water repellency at and below the soil surface in two coastal sandy podzols following bushfire. Water drop penetration time tests were applied to burned and unburned soils at a high dune field site in South East Queensland, Australia. It was found that the mean water drop penetration time of the burned soil was four times that of the unburned soil, but both soils were largely non‐repellent. Post‐fire repellency peaked below the surface in a patchy layer, in contrast to the laterally extensive layer reported in other studies, and high organic matter content in the soil did not appear to significantly influence repellency post‐burn. Non‐parametric statistics were used to quantify the high spatial variability in water repellency, which was ultimately insufficiently captured by atypically large (n = 1000 drop) datasets. This study confirms the presence of naturally occurring repellency and patchy infiltration in sandy soils while demonstrating that conclusively describing the influence of fire is challenging in a soil with heterogeneous infiltration characteristics. With respect to this uncertainty, it appears that fire does not increase soil water repellency such that infiltration and runoff processes due to fire‐induced water repellency would differ post‐burn.  相似文献   

Geomorphic influences on the distribution and accumulation of pyrogenic carbon (PyC) following a low severity wildfire in northern New Mexico          下载免费PDF全文

Amy Galanter  Daniel Cadol  Kathleen Lohse 《地球表面变化过程与地形》2018,43(10):2207-2218

The distribution, transport, and accumulation of wildfire‐generated pyrogenic carbon (PyC) has important consequences for contaminant transport and carbon cycling, but a conceptual model for PyC accumulation and loss that includes geomorphic processes is lacking. In this study we quantified PyC concentration in soil samples collected from the Jemez Mountains of New Mexico before and after the 2013 Thompson Ridge (TR) fire, and developed a conceptual model describing PyC redistribution. Pre‐fire samples were fortuitously collected 4 years before the TR burn and post‐fire samples were collected at the same locations 15 months following the TR fire. Samples were collected from the O and A horizon, with sites representing a range of slope angle, aspect, burn severity, and geomorphic setting. PyC was determined by a modified chemo‐thermal oxidation method to compare PyC to total organic carbon (TOC). The mean PyC/TOC ratio was significantly higher post‐fire than pre‐fire (0.14 vs 0.12), indicating increased PyC sequestration. O horizon PyC concentrations were more variable and more responsive to fire than the A horizon. Soil horizon, watershed, and geomorphic setting proved to be the most influential factors in predicting PyC concentration changes. PyC concentrations increased most on hillslopes and in low‐severity burn areas, suggesting higher rates of PyC production or post‐fire accumulation. Burn patchiness appears to facilitate PyC accumulation, with lower severity patches trapping PyC mobilized from high severity patches. While PyC content had greater point scale variance following the fire, the fire also homogenized pre‐fire PyC differences between soil horizons and among watersheds within the burn perimeter, differences that appear to develop over time between fires. The O horizon is a larger sink for PyC in the short term following fire, but based on pre‐fire concentrations the A horizon appears to be a more stable sink for PyC. Copyright © 2018 John Wiley & Sons, Ltd.  相似文献   

Sourcing little Colorado white ware: A regional approach to the compositional analysis of prehistoric ceramics     

Amy A. Douglass  David M. Schaller 《Geoarchaeology》1993,8(3):177-201

Little Colorado White Ware (LCWW) is a decorated black-on-white ceramic constructed by the Anasazi in the southwestern United States from approximately A. D. 1050 to 1250. LCWW potsherds are found in archaeological sites located throughout the Little Colorado River valley of northern Arizona. Two major volcanic fields which are located on opposite sides of the Little Colorado River, the San Francisco Peaks in the west and the Hopi Buttes in the east, have been proposed as source areas for LCWW production. Petrographic, X-ray diffraction, and electron microprobe analyses of this ware's raw material constituents and geologic samples indicate that LCWW could only have been produced in the Hopi Buttes area. This study is presented as an example of a research design whose sample size, geographic scale, and methodologies can be effective in determining the source of prehistoric ceramics from the southwestern United States and elsewhere. © 1993 John Wiley & Sons, Inc.  相似文献   

Eurasian snow cover variability and links to winter climate in the CMIP5 models     

Jason C. Furtado  Judah L. Cohen  Amy H. Butler  Emily E. Riddle  Arun Kumar 《Climate Dynamics》2015,45(9-10):2591-2605

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Erratum to: An experimental study of Ti and Zr partitioning among zircon,rutile, and granitic melt     

Amy E. Hofmann  Michael B. Baker  John M. Eiler 《Contributions to Mineralogy and Petrology》2015,169(5):1-1

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Managing Bay and Estuarine Ecosystems for Multiple Services     

Lisa A. Needles  Sarah E. Lester  Richard Ambrose  Anders Andren  Marc Beyeler  Michael S. Connor  James E. Eckman  Barry A. Costa-Pierce  Steven D. Gaines  Kevin D. Lafferty  Hunter S. Lenihan  Julia Parrish  Mark S. Peterson  Amy E. Scaroni  Judith S. Weis  Dean E. Wendt 《Estuaries and Coasts》2015,38(1):35-48

Managers are moving from a model of managing individual sectors, human activities, or ecosystem services to an ecosystem-based management (EBM) approach which attempts to balance the range of services provided by ecosystems. Applying EBM is often difficult due to inherent tradeoffs in managing for different services. This challenge particularly holds for estuarine systems, which have been heavily altered in most regions and are often subject to intense management interventions. Estuarine managers can often choose among a range of management tactics to enhance a particular service; although some management actions will result in strong tradeoffs, others may enhance multiple services simultaneously. Management of estuarine ecosystems could be improved by distinguishing between optimal management actions for enhancing multiple services and those that have severe tradeoffs. This requires a framework that evaluates tradeoff scenarios and identifies management actions likely to benefit multiple services. We created a management action-services matrix as a first step towards assessing tradeoffs and providing managers with a decision support tool. We found that management actions that restored or enhanced natural vegetation (e.g., salt marsh and mangroves) and some shellfish (particularly oysters and oyster reef habitat) benefited multiple services. In contrast, management actions such as desalination, salt pond creation, sand mining, and large container shipping had large net negative effects on several of the other services considered in the matrix. Our framework provides resource managers a simple way to inform EBM decisions and can also be used as a first step in more sophisticated approaches that model service delivery.  相似文献   

Environmental learning and the social construction of an exurban landscape in Fremont County, Colorado   总被引：1，自引：0，他引：1  

Soren C. Larsen  Matt Foulkes  Amy Thompson 《Geoforum》2011,42(1):83-93

Across the rural American West, the restructuring of rural capitalism has transformed production landscapes into those increasingly structured by the development and consumption of natural and cultural amenities. This project used principles from symbolic interactionism, ethnographic methods, and the analytical framework of regional political ecology to understand the role of environmental learning in negotiating the new management regime associated with amenity-based capitalism in rural Fremont County, Colorado. The study found that most amenity residents participate regularly in social learning about the environment through a variety of interpersonal and organizational behaviors. In addition, they are responding collectively to environmental risks and opportunities associated with wildfire, noxious weeds and invasive grass species, prospective uranium mining, and restoration of cultural-landscape features. Ultimately, the practices of environmental learning concern how private properties and assets will be managed relative to the social construction of the environment as an amenity for personal consumption. Conservation and management prospects in this and other rural areas in the postindustrial world can be enhanced by understanding the microsociology of exurban geographies and by engaging the social forms and processes related to this distinctive landscape construction.  相似文献   

New optically stimulated luminescence ages provide evidence of MIS3 and MIS2 eolian activity on Black Mesa, northeastern Arizona, USA     

Amy L. Ellwein  Shannon A. Mahan  Leslie D. McFadden 《Quaternary Research》2011,75(3):395-398

Eolian deposition on the semiarid southern Colorado Plateau has been attributed to episodic aridity during the Quaternary Period. However, OSL ages from three topographically controlled (e.g. falling) dunes on Black Mesa in northeastern Arizona indicate that eolian sediments there were deposited in deep tributary valleys as early as 35–30 ka, with most sand deposited before 20 ka. In contrast, the oldest OSL ages for sand sheets fall within the Pleistocene-Holocene climatic transition (~ 12–8 ka). Thus most eolian sediment accumulated on Black Mesa under climatic conditions that were in general cooler, moister, and more variable than today, not more arid, pointing to a considerable increase in sediment supply.  相似文献   

Aquifer recharge and recovery: groundwater recharge systems for treatment, storage, and water reclamation     

Missimer TM  Drewes JE  Maliva RG  Amy G 《Ground water》2011,49(6):771-771

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