Detrital zircon geochronology of Palaeozoic Novaya Zemlya – a key to understanding the basement of the Barents Shelf     

Henning Lorenz  David G. Gee  Evgeny Korago  Galina Kovaleva  William C. McClelland  Jane A. Gilotti  Dirk Frei 《地学学报》2013,25(6):496-503

The Novaya Zemlya fold‐and‐thrust‐belt is the northern continuation of the late Palaeozoic Uralide Orogen. Little is known about its deeper structure and the basement history of the adjacent Barents and Kara shelves. Based on geological evidence and detrital zircon analysis of 28 samples from the northeastern and stratigraphically deepest part of the archipelago, we demonstrate that Cambro‐Ordovician turbidite‐dominated deposition was almost exclusively sourced from rocks consolidated during the Timanian orogeny (Timanian basement). A profound change in provenance occurred near the end of the Ordovician. Over 90% of the zircons from Silurian and about 80% from Devonian strata have ages characteristic of the Sveconorwegian Orogen, implying uplift of these rocks in the vicinity of Novaya Zemlya. The presence of Sveconorwegian and Grenvillian rocks in the high Arctic suggests revision of recent reconstructions of the Rodinia supercontinent, its break‐up and subsequent Caledonian orogeny.  相似文献   

Disposition of polycyclic aromatic compounds in blue crabs,Callinectes sapidus,from the southern Chesapeake Bay     

Robert C. Hale 《Estuaries and Coasts》1988,11(4):255-263

The blue crab,Callinectes sapidus, is an abundant and widely distributed species in the Chesapeake Bay. It also supports a valuable fishery. Minimal information concerning concentrations of toxic organic compounds in crustaceans of the southern Chesapeake Bay is currently available. As a consequence, a study to determine the tissue burdens and behavior of lipophilic polycylic aromatic compounds (PACs) in these organisms was undertaken. Highest concentrations of PACs were detected in hepatopancreas, followed by ovarian and muscle tissues. Extractable lipid levels in the tissues were positively correlated with organic xenobiotic concentrations. The major contaminants detected in blue crabs sampled from the southern bay were alkylated PACs, as opposed to unsubstituted polynuclear aromatic hydrocarbons which have been reported to predominate in molluscs and sediments of the bay. This dichotomy may be due to differences in contaminant bioavailability or in the relative abilities of the organisms to eliminate xenobiotics. Crabs from both heavily industrialized and relatively undeveloped areas, showed evidence of exposure. These data suggest that localized areas of contamination and episodic contaminant releases may result in xenobiotic body burdens in mobile/migratory species. Crabs acutely exposed to radiolabeled benzo(a)pyrene in the laboratory were capable of rapid bioaccumulation. After transfer to clean water, the organisms efficiently eliminated this material, although at a rate slower than that observed for accumulation. Evidence that ecdysis in crustaceans may affect the disposition of PACs was also witnessed in these experiments. Differences in tissue concentrations of benzo(a)pyrene derived material were observed between crabs of various sex, maturity, and molt stages.  相似文献   

Reaction progress during mylonitization of basaltic dikes along the Särv thrust,Swedish Caledonides     

Jane A. Gilotti 《Contributions to Mineralogy and Petrology》1989,101(1):30-45

The mylonite zone at the base of the Särv thrust sheet, Swedish Caledonides, contains diabase dikes which record intense deformation and syntectonic greenschist facies metamorphism. An angular shear strain of 100 is calculated for a single dike which can be followed for 50 m in the mylonite zone and abundant centimeter thick greenschist layers imply shear strains in excess of 1000. This extraordinary amount of deformation is comparable to the largest strains attained during experimental superplastic deformation of metals and alloys and, by analogy, suggests that dike deformation was macroscopically superplastic. The progress of five syntectonic reactions was measured as a function of increasing strain for the continuously exposed dike in order to assess the contribution of reactionenhanced ductility and fluid-rock interactions to strain localization along the thrust. Reaction progress calculations suggest that the breakdown of amphibole to form weaker phyllosilicates (which are added to the incompetent matrix fraction) is the important strain softening mechanism below 100. The ultimate tectonite is a stable biotite-epidote schist comprised of a uniformly fine grain size (< 200 m), constant grain shapes and strain free grains. Below 40, metamorphism was isochemical and shear strain was independent of H₂O in the reactions. Petrologic fluid:rock ratios are low and suggest that deformation could have occurred under relatively dry conditions.Deformation micromechanisms were probably dominated by diffusive mass transfer processes throughout the life of the shear zone. The absence of cataclasis and the fine grain size of the protolith basalt suggest that fluids were introduced via grain boundary diffusion. Incongruent pressure solution at low strains and K-metasomatism above 40 also support diffusional flow. Diffusion-accomodated grain boundary sliding is thought to be the dominant micromechanism once the stable biotite-epidote tectonite forms.  相似文献   

Survey of Microbial Populations in Buried-Valley Aquifer Sediments from Northeastern Kansas   总被引：1，自引：0，他引：1  

James L. Sinclair  Stephen J. Randtke  Jane E. Denne  Lawrence R. Hathaway  William C. Ghiorse 《Ground water》1990,28(3):369-377

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The intensity of the geomagnetic field at 3.5 Ga: paleointensity results from the Komati Formation, Barberton Mountain Land, South Africa     

C.J. Hale 《Earth and Planetary Science Letters》1987,86(2-4)

Paleointensity measurements have been carried out on 3.5 Ga samples from the Komati Formation type locality using both the Thellier and Van Zijl methods. These samples contain a single steeply-directed negative TRM component acquired during metamorphism of the Komati lavas. Thellier experiments yielded values ranging from 12 to 37 μT but an average paleofield intensity for the four best determinations is 20 ± 3 μT. A slightly lower average paleointensity of 15 ± 3 μT was obtained using Van Zijl experiments. Preheating was used to chemically stabilize seven samples used in Van Zijl determinations and these produced nearly ideal plots with an average paleointensity of 13 ± 2 μT. A single basaltic komatiite sample gave a nearly ideal Van Zijl plot indicating about 21 μT, nearly the same paleointensity as the peridotitic komatiite samples even though its NRM intensity was several orders of magnitude lower. Since the Komati characteristic remanence was acquired during a slow cooling, the data must be reduced by a factor of 1.55 to account for the difference between laboratory and natural cooling rates. Calculation of an equivalent equatorial paleointensity using the paleolatitude implied by the steep Komati characteristic remanence then gives value of 5 μT for the intensity of the geomagnetic field at 3.5 Ga, lower than the present value of about 30 μT.  相似文献   

Detecting Changes in Ground Water Quality at Regulated Facilities     

Jim C. Loftis  Jane Harris  Robert H. Montgomery 《Ground Water Monitoring & Remediation》1987,7(1):72-76

The Resource Conservation and Recovery Act (PL 94–580) and related federal and state legislation have mandated routine monitoring of ground water quality at regulated facilities. The objective of the required monitoring activities is detection of adverse changes in ground water quality caused by the facilities.
Both failure to detect pollution and an incorrect determination of pollution can be very expensive. It is crucial, therefore, that monitoring programs be designed and operated to provide statistically sound information. It is equally important that users of ground water quality data understand the nature and limitations of information from monitoring.
To address the preceding issues, the authors present a general approach to analyzing ground water quality data in light of the stated monitoring objective. The suggested approach accounts for "natural" variation in background water quality through pairing of observations. The limitations of quarterly sampling for detecting small changes in quality over a short time frame are discussed.  相似文献   

Quaternary evolution of the great lakes : Edited by P. F. Karrow and P. E. Calkin. Geological association of Canada special paper 30, London, Ontario, 1985, 258 pp     

Jane L. Forsyth 《Quaternary Research》1987,28(3)

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Subtidal distribution of barnacles (Cirripedia: Balanidae) in Chesapeake Bay,Maryland     

Victor S. Kennedy  Jane DiCosimo 《Estuaries and Coasts》1983,6(2):95-101

From 1977 to 1980, samples of barnacles were collected (as opportunities arose) from 61 subtidal locations (mostly oyster beds) around Chesapeake Bay, Maryland. Three species were identified from the area.Balanus improvisus dominated, comprising 83% of the 8,231 barnacles identified, and was collected at all locations but one. It occurred over a collection salinity range of 0.8‰ to 17.9‰.Balanus subalbidus (14% of the barnacles identified) was collected over the same salinity range, but mainly in lower salinity waters.Balanus eburneus was scarce (2% of the barnacles identified) and was collected at higher salinities (8.5‰ to 17.1‰).  相似文献   

The influence of viscous and latent heating on crystal-rich magma flow in a conduit     

Alina J. Hale  Geoff Wadge  Hans B. Mühlhaus 《Geophysical Journal International》2007,171(3):1406-1429

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Preface     

Thomas D. Demchuk  Jane C. Shearer  Timothy A. Moore 《International Journal of Coal Geology》1995,28(2-4)

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