Bathymetric mapping and sub-bottom profiling through lake ice with ground-penetrating radar   总被引：2，自引：1，他引：2  

Brian J. Moorman  Frederick A. Michel 《Journal of Paleolimnology》1997,18(1):61-73

Bathymetric mapping of lakes with sonar is essentially limited to the ice-free summer months. Recent developments in ground-penetrating radar technology have greatly increased its portability and capabilities for imaging through fresh water. The suitability of a backpack portable ground-penetrating radar (GPR) system for bathymetric mapping of ice-covered Arctic lakes was investigated by performing grid surveys on three lakes with water depths up to 19 m. It was demonstrated that GPR can now be used to quickly produce high quality bathymetric maps and sub-bottom profiles showing sediment type and lacustrine sediment thickness. While water depths were measured with a precision of ±3%, lacustrine sediment thickness measurements (up to 5 m) had an estimated precision of ±15%.  相似文献   

The relative importance of biotic and abiotic vectors in nutrient transport     

Keith L. Bildstein  Elizabeth Blood  Peter Frederick 《Estuaries and Coasts》1992,15(2):147-157

The mass of nutrients (nitrogen, phosphorus, potassium, and calcium) imported during 1984 and 1985 to the North. Inlet Estuary, Georgetown County, South Carolina, by precipitation and runoff was compared with that imported by a colonial-nesting wading bird, the white ibis (Eudocimus albus). From late March through late June of both years, breeding ibises imported nutrients to the North Inlet Estuary study site from freshwater bottomland forest swamps, where they fed on crayfishes (Procambaridae). Although 1984 was a relatively wet year, in 1985 the ibis breeding season was preceded by a severe winter-spring drought. In 1984 ibises nested in higher numbers, had higher per-pair breeding success, and imported 11 times more nutrients than in 1985. Nutrient input from atmospheric sources was substantially lower in 1984 than in 1985. The 1984 ibises imported 9% as much nitrogen, 33% as much phosphorus, 0.4% as much potassium, and 0.3% as much calcium to the estuary as did atmospheric sources. In 1985 nutrient input from ibises amounted to only 0.2% of the nitrogen, 2.9% of the phosphorus, and ?1% of the potassium and calcium imported by atmospheric sources. Our results show that nutrient inputs to estuaries from colonial-nesting wading birds can be substantial when compared, with those from atmospheric sources and can vary considerably among years. They also suggest that nutrient regimes in estuaries with large assemblages of wading birds may differ significantly from those lacking such colonies. *** DIRECT SUPPORT *** A01BY058 00006  相似文献   

Delta Smelt Habitat in the San Francisco Estuary: A Reply to Manly,Fullerton, Hendrix,and Burnham’s “Comments on Feyrer et al. Modeling the Effects of Future Outflow on the Abiotic Habitat of an Imperiled Estuarine Fish”     

Frederick Feyrer  Ken Newman  Matthew Nobriga  Ted Sommer 《Estuaries and Coasts》2016,39(1):287-289

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An experimental study of the partitioning of a rare earth element (Gd) in the system diopside—aqueous vapour     

Robert A. Zielinski  Frederick A. Frey 《Geochimica et cosmochimica acta》1974,38(4):545-565

The partitioning of Gd in the experimental system diopside-aqueous vapor as a function of temperature, pressure, composition of the phases, time, grain size, solid-liquid ratio and Gd concentration has been investigated. A radioactive tracer measurement was used to determine Gd concentration in the separated phases. Diposides were reacted with aqueous vapor containing tracer Gd and reversibility was tested by reacting Gd-doped diopsides with pure aqueous vapor. Equilibration of Gd between the bulk of the diopside and the liquid was found to be limited by the slow rate of Gd diffusion in diopside, maximum value of D = 2 × 10^?15cm²sec^?1 at 800°C and 1 kb. Depending on whether the diopside was previously synthesized or synthesized from an oxide mix during the experiment, Gd concentrations were zoned in the crystal such that higher concentrations existed at the edges or center, respectively. Equilibrium is difficult to achieve in these experiments, but at the optimum experimental conditions for equilibration, the Gd diopside-aqueous vapor distribution coefficient is 20 ± 6 (800°C, 1 kb) in approximate agreement with previous results of 55 ± 23. Changing the composition of the aqueous vapor indicated that possible mechanisms for Gd substitution included coupling of Gd³⁺ with H⁺ or Na⁺ replacing 2Ca²⁺, or substitution of 2Gd³⁺ for 3Ca²⁺ with formation of a cation vacancy.  相似文献   

Urban Growth And Land Value Patterns: Government Influences *     

Frederick W. Boal 《The Professional geographer》1970,22(2):79-82

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Long excursion to keswick: Monday,August 20th,to Saturday,August 25th, 1900     

John E. Marr  Frederick Meeson 《Proceedings of the Geologists' Association. Geologists' Association》1900,16(10):526-IN1

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Excursion to Central Brittany     

P. Lebesconte  T. Bezier  Frederick Meeson 《Proceedings of the Geologists' Association. Geologists' Association》1899,16(5):240-242

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Long excursion to the Lake District: August 7th to 17th, 1920     

J. Frederick N. Green 《Proceedings of the Geologists' Association. Geologists' Association》1921,32(3):123-IN1

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Optimum design of Ocean bottom seismometers     

George H. Sutton  Frederick K. Duennebier 《Marine Geophysical Researches》1987,9(1):47-65

Ocean bottom seismometers (OBS) have been widely used during the past decade to collect seismic data for determination of the structure of the oceanic lithosphere, stress patterns in regions of earthquake activity, and geoacoustic parameters of the ocean floor. Data quality from these experiments has often been disappointing because of poor signal quality and high noise levels. Many of these problems result from motion of the OBS package that is decoupled from motion of the ocean floor. These coupling problems are more serious in the ocean than on land because of the low shear strengths of most ocean sediments. In this paper we continue to develop the theory of coupling of OBSs to soft sediments and arrive at results suggesting that OBS packages should be designed with: (1) the minimum mass possible, (2) radius of area in contact with the sediment proportional to the cube root of the mass, and the maximum radius less than 1/4 of the shear wavelength, (3) density of the OBS approximately that of the sediment, (4) a low profile and a small vertical cross section with water, and (5) low density gradients, and maximum symmetry about the vertical axis. Agreement of the theory with test data is good; most deviations are reasonable, given limitations of the theory and experiments. The theory also suggests that the coupling frequency, the frequency above which the OBS does not follow the motion of the sediment, is directly proportional to the sediment shear velocity.  相似文献   

Gravity-flow deposits from the St. Croix Ridge: Depositional history     

Troy L. Holcombe  Cynthia G. Fisher  Frederick A. Bowles 《Geo-Marine Letters》1989,9(1):11-18

Gravity-flow sediments from the South Virgin Islands Trough Escarpment (west of the island of St. Croix) contain Late Cretaceous through Late Miocene nannofossils that are well mixed even within individual samples. These sediments, reworked and redeposited in latest Miocene or Early Pliocene, apparently occur within a sequence of Late Miocene-to-recent fan deposits. Marine source beds representing all pre-Pliocene epochs of the Cenozoic and latest Cretaceous must have been exposed along the NW-facing West St. Croix Escarpment. Southward tilting of the St. Croix Ridge has subsequently altered the depositional pattern.  相似文献