Evidence for high water levels in the Erie basin during the Younger Dryas chronozone     

Keith J. Tinkler  James W. Pengelly  William G. Parkins  Jaan Terasmae 《Journal of Paleolimnology》1992,7(3):215-234

A high water phase in the Lake Erie basin is identified from a variety of evidence for the period 11.0 ka to 10.5 ka. It is believed to correspond to the first Agassiz inflow to the upper Great Lakes (Main Lake Algonquin phase) when Agassiz waters discharged in both catastrophic and equilibrium modes to Lake Superior. After allowing for differential isostatic rebound, a computational model is used to estimate the lake levels in the Erie basin needed to generate Agassiz-equivalent discharges out of the basin into Lake Ontario. Computations suggest that Lake Tonawanda spillways would be re-activated by the high lake levels needed to sustain Agassiz-equivalent discharges. Existing published evidence from the Erie basin, Niagara River, and western New York (including ¹⁴C dates), is consistent with this interpretation. Additional evidence from the Niagara Peninsula (pollen spectra and geomorphology) supports the inference that extensive flooding of the southern Niagara Peninsula (Lake Wainfleet) occurred due to high water levels in the Erie basin. In the Niagara Peninsula, very shallow washover spillways would only operate when standard hydrologic variations of lake level in the Erie basin coincided with short term high levels driven by catastrophic inflows to the Great Lakes from Lake Agassiz. We support the view of Lewis & Anderson (1992) that a meltwater flux from Agassiz inflows reached Lake Erie.  相似文献   

Transport of stable isotopes,kinetics, dispersive advection,and the ‘isotopic fronts’ of Baumgartner and Rumble (1988)     

Peter Blattner  Keith R. Lassey 《Contributions to Mineralogy and Petrology》1990,105(4):486-490

Baumgartner and Rumble (1988) apply a kinetic continuum theory for stable isotope transport to unidimensional infiltration of fluid into rock. Their numerical applications are restricted to the simplified case of rapid isotope exchange between phases, where the sharp isotope fronts of pure advection are distended by dispersive mechanisms only. However, kinetic limitations of isotope exchange are potentially an equally important distending mechanism, and it will only rarely be possible to ascribe front gradients to diffusion/dispersion alone. Abrupt isotopic changes at vein boundaries are more often a secondary signal of lithologic change than the expression of a retarded advective front. At such boundaries, diffusion and dispersion play a role that is comparable to, or greater than, that of advection, so that the detailed shapes of isotope fronts depend upon boundary conditions for the infiltration process. Zerodimensional box models have legitimate, if limited, uses in the modelling of fluid-rock interaction, and are reexamined.  相似文献   

Age constraints on Pleistocene megafauna at Tight Entrance Cave in southwestern Australia     

Linda K. Ayliffe  Gavin J. Prideaux  Michael I. Bird  Rainer Grün  Richard G. Roberts  Grant A. Gully  Rhys Jones  L. Keith Fifield  Richard G. Cresswell   《Quaternary Science Reviews》2008,27(17-18):1784-1788

A well-stratified succession of fossiliferous sediments occurs in Tight Entrance Cave, southwestern Australia. These infill deposits contain the remains of megafauna and have accumulated intermittently since the Middle Pleistocene: >137, 137–119 and 50–29 ka, according to the results of ¹⁴C, U–Th, ESR and OSL dating techniques. Megafaunal species richness was highest in the latest part of the penultimate glacial maximum and during the subsequent last interglacial (137–119 ka), but remains are less abundant following an apparent 70 ka depositional hiatus in the sequence. Most megafaunal specimens from the upper (<44 ka) units are fragmentary, and reworking from older strata cannot yet be ruled out. However, one specimen of Simosthenurus occidentalis (a large extinct kangaroo), a pair of articulated dentaries showing no signs of secondary transportation, was found within a sedimentary layer deposited between 48 and 50 ka. This represents one of the youngest demonstrably in situ occurrences of an Australian megafaunal taxon.  相似文献   

Defining a Digital Earth System   总被引：1，自引：0，他引：1  

Karl E. Grossner  Michael F. Goodchild  Keith C. Clarke 《Transactions in GIS》2008,12(1):145-160

In a 1998 speech before the California Science Center in Los Angeles, then US Vice‐President Al Gore called for a global undertaking to build a multi‐faceted computing system for education and research, which he termed “Digital Earth.” The vision was that of a system providing access to what is known about the planet and its inhabitants’ activities – currently and for any time in history – via responses to queries and exploratory tools. Furthermore, it would accommodate modeling extensions for predicting future conditions. Organized efforts towards realizing that vision have diminished significantly since 2001, but progress on key requisites has been made. As the 10 year anniversary of that influential speech approaches, we re‐examine it from the perspective of a systematic software design process and find the envisioned system to be in many respects inclusive of concepts of distributed geolibraries and digital atlases. A preliminary definition for a particular digital earth system as: “a comprehensive, distributed geographic information and knowledge organization system,” is offered and discussed. We suggest that resumption of earlier design and focused research efforts can and should be undertaken, and may prove a worthwhile “Grand Challenge” for the GIScience community.  相似文献   

The July 2007 rock and ice avalanches at Mount Steele, St. Elias Mountains, Yukon, Canada   总被引：1，自引：0，他引：1  

Panya S. Lipovsky  Stephen G. Evans  John J. Clague  Chris Hopkinson  Réjean Couture  Peter Bobrowsky  Göran Ekström  Michael N. Demuth  Keith B. Delaney  Nicholas J. Roberts  Garry Clarke  Andrew Schaeffer 《Landslides》2008,5(4):445-455

A large rock and ice avalanche occurred on the north face of Mount Steele, southwest Yukon Territory, Canada, on July 24, 2007. In the days and weeks preceding the landslide, several smaller avalanches initiated from the same slope. The ice and rock debris traveled a maximum horizontal distance 5.76 km with a maximum vertical descent of 2,160 m, leaving a deposit 3.66 km² in area on Steele Glacier. The seismic magnitude estimated from long-period surface waves (M _s) is 5.2. Modeling of the waveforms suggests an estimated duration of approximately 100 s and an average velocity of between 35 and 65 m/s. This landslide is one of 18 large rock avalanches known to have occurred since 1899 on slopes adjacent to glaciers in western Canada. We describe the setting, reconstruct the event chronology and present a preliminary characterization of the Mount Steele ice and rock avalanches based on field reconnaissance, analysis of seismic records and an airborne LiDAR survey. We also present the results of a successful dynamic simulation for the July 24 event.  相似文献   

Further testing of the Integrated Hydrology Model (InHM): event‐based simulations for a small rangeland catchment located near Chickasha,Oklahoma     

Keith Loague  Christopher S. Heppner  Robert H. Abrams  Adrianne E. Carr  Joel E. VanderKwaak  Brian A. Ebel 《水文研究》2005,19(7):1373-1398

In the paper that is the foundation for this study, VanderKwaak and Loague (2001. Water Resources Research 37 : 999–1013) reported a demonstration of a fully coupled comprehensive physics‐based hydrologic‐response model, InHM (Integrated Hydrology Model), for two rainfall‐runoff events from the small rangeland catchment known as R‐5. The InHM simulations reported herein address (in three phases) limitations in the VanderKwaak and Loague (2001. Water Resources Research 37 : 999–1013) simulations. In Phase I, a new finite‐element mesh was selected to represent R‐5. In Phase II, with the new mesh in place, evaporation was considered for the R‐5 events. In Phase III, with the new mesh in place and evaporation considered, the geology of R‐5 was approximated. Each phase, compared with the results reported by VanderKwaak and Loague (2001. Water Resources Research 37 : 999–1013), shows a change in the simulated near‐surface response. The performance of InHM for 15 R‐5 events is also reported herein. The results from two stages of model calibration are presented. The uncertainty in initial soil‐water content estimates for event‐based simulation is shown to be a major limitation for physics‐based models. The performance of InHM, relative to past event‐based simulation efforts with a quasi‐physically based rainfall‐runoff model, is better for both peak stormflow and the time to peak stormflow, but worse for stormflow depth. The InHM simulations reported here set the stage for continuous simulation of near‐surface response for the R‐5 catchment with InHM. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Estimating In-Situ Monod Biodegradation Parameters Using a Novel Explicit Solution of a One-Dimensional Contaminant Transport Equation     

Chetan T. Goudar  Keith A. Strevett 《Ground water》2000,38(6):894-898

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Source Wavelet Phase Extraction     

Diako Hariri Naghadeh  Christopher Keith Morley 《Pure and Applied Geophysics》2016,173(6):2011-2032

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Setting limits for acceptable change in sediment particle size composition following marine aggregate dredging     

Cooper KM 《Marine pollution bulletin》2012,64(8):1667-1677

In the UK, Government policy requires marine aggregate extraction companies to leave the seabed in a similar physical condition after the cessation of dredging. This measure is intended to promote recovery, and the return of a similar faunal community to that which existed before dredging. Whilst the policy is sensible, and in line with the principles of sustainable development, the use of the word 'similar' is open to interpretation. There is, therefore, a need to set quantifiable limits for acceptable change in sediment composition. Using a case study site, it is shown how such limits could be defined by the range of sediment particle size composition naturally found in association with the faunal assemblages in the wider region. Whilst the approach offers a number of advantages over the present system, further testing would be required before it could be recommended for use in the regulatory context.  相似文献   

"Update on the use of the RORA program for recharge estimation", by Al Rutledge May-June 2007 issue, v. 45, no.3: 374-382     

Halford KJ 《Ground water》2008,46(1):10-1; author reply 11-2

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