Discussion on the paper by Denton and Hughes (1983)     

J. T. Andrews  G. H. Miller   《Quaternary Research》1985,24(3):361-364

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The Puncoviscana trough — a large basin of Late Precambrian to Early Cambrian age on the pacific edge of the Brazilian shield     

Pavel JeŽek Dipl.-Geol.  Dr. Arne P. Willner  Prof. Dr. Florencio G. AceÑolaza  Prof. Dr. Hubert Miller 《International Journal of Earth Sciences》1985,74(3):573-584

During the Late Precambrian to Early Cambrian a large basin with a homogeneous psammitic-pelitic sediment fill existed in the area of the NW-Argentine Andes. It is now exposed in different tectonic levels. This basin of meridional elongation was situated on a stable continental margin at the western edge of the Brazilian shield. It was underlain by segmented older continental crust. According to the modal and chemical composition of the greywackes and subgreywackes a predominant metasedimentary source may be supposed. Four clastic facies types indicate a transport by gravity currents within a submarine fan system, while massive red pelites represent cut-off periods, and rare carbonates deposition on rises. The gravity currents derived from easterly directions. The sedimentation age is proved by a rich ichnofauna and some medusoid impressions.

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Zusammenfassung Im Jungpräkambrium bis Unterkambrium existierte im Bereich der NW-argentinischen Anden ein ausgedehnter Trog mit homogener psammitisch-pelitischer Füllung, die heute in verschiedenen Gebirgsstockwerken aufgeschlossen ist. Dieses Becken lag an einem stabilen Kontinentalrand im Westen des Brasilianischen Schildes und war von segmentierter älterer, kontinentaler Kruste unterlagert. Nach der modalen und chemischen Zusammensetzung der Grauwacken und Subgrauwacken sind überwiegend metasedimentäre Herkunftsgesteine anzunehmen. Vier klastische Faziestypen lassen auf Transport durch Trübeströme in submarine Fächer schließen, während mächtige Rotpelite Ruhezeiten und die seltenen Karbonate Ablagerungen auf Schwellen anzeigen. Die Schüttungen stammen aus östlichen Richtungen. Das Sedimentationsalter ist durch eine reichhaltige Ichnofauna und einige Medusenabdrücke dokumentiert.

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Résumén Durante el Precámbrico superior hasta el Cámbrico inferior en los Andes del NW Argentino se extendía una larga cuenca rellena de sedimentos psamo-pelíticos homogéneos, que hoy afloran en distintos pisos tectónicos. Esta cuenca de elongación meridional estaba situada en un margen continental estable al lado occidental del escudo brasileño, sobre corteza continental segmentada más antigua. Según su composición modal y química, las grauvacas y subgrauvacas derivaron predominantemente de rocas metasedimentarias. Cuatro tipos de facies clásticas indican su transporte en corrientes de gravedad, provenientes del este, y sedimentación en conos submarinos. Pelitas rojas macizas representan períodos de sedimentación pelágica, mientras que los escasos carbonatos se depositaron en dorsales. Una icnofauna amplia y algunas impresiones de medusoides documentan la edad de sedimentación.

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Zircon U-Pb ages of the Franzfontein granitic suite,northern South West Africa     

A.J. Burger  T.N. Clifford  R.McG. Miller 《Precambrian Research》1976,3(5):415-431

U-Pb isotopic data are presented for composite and size fractions of zircons from 15 samples of the Franzfontein granitic suite. These data reveal two distinctly different discordance trends that yield concordia intercept ages of 1730±30 m.y. and 1870±30 m.y. that are believed to encompass the age of emplacement of the suite. The previously published Rb-Sr isochron age of 1580±20 m.y. is now interpreted as recording a time of Rb and/or Sr migration through the system. The stratigraphic implications of the new zircon data are discussed.  相似文献   

Internal airflow of a convective storm from dual-Doppler radar measurements     

L. J. Miller 《Pure and Applied Geophysics》1975,113(1):765-785

The dual-Doppler radar coplane method of scanning and data reduction has been used to determine the internal airflow and radar reflectivity structure of a convective storm. Cumulus convection growing in a moderately sheared wind environment resulted in a nonsteady, moderate intensity thunderstorm. Precipitation fallout and downward moving air are found downshear of an updraft inclined in the downshear direction. Rapid storm translation, vertical shear of the ambient wind, and slow subcloud ascent of inflow air act to establish this observed draft configuration. The absence of significant cold air outflow and its attendant gust front at the surface is attributed to (i) appreciable inflow of slow moving air into the downdraft at the middle layers and (ii) the fact that the potentially coldest air was located too low to contribute significantly to a deep downdraft circulation.  相似文献   

Satellite Measurements of Albedo and Radiant Temperature from Semi-Desert Grassland along the Arizona/Sonora Border     

Jeffrey L. Michalek  John E. Colwell  Norman E. G. Roller  Nicole A. Miller  Eric S. Kasischke  William H. Schlesinger 《Climatic change》2001,48(2-3):417-425

Along the international border separatingthe U.S. (Arizona) and Mexico (Sonora), differencesin the grazing intensity of domestic livestock arecommonly presumed to have created a large differencein vegetation cover between the two countries. Thisvegetation difference is reportedly responsible for anextensive albedo and temperature discontinuity thatmay be affecting regional climate. In this study, weused Landsat Thematic Mapper data to examinetrans-border differences in these two biophysicalparameters. Albedo and radiant temperature estimateswere computed for 25 km-long (east-west) transectsthrough semi-desert grassland on each side of theborder at two different times of year. Only smallaverage trans-border differences in these parameterswere found, and in some cases average albedo andtemperature data were essentially equal on each sideof the border. In addition, we found significantspatial heterogeneity in conditions on both sides ofthe border. These results suggest that, based on asmall sample, it may be difficult to assess whetherthere are significant differences in biophysicalproperties of semi-arid grassland between Arizona andMexico in the vicinity of the border. We concludethat more extensive spatial and temporal sampling iscritical in assessing any possible trans-borderdifferences in average terrain conditions that mightaffect climate, and that this data must be coupledwith more extensive meteorological data to assesswhether a difference in climate also exists.  相似文献   

Comparative reproductive success of winter flounder in Long Island Sound: A three-year study (biology,biochemistry, and chemistry)     

D. A. Nelson  J. E. Miller  D. Rusanowsky  R. A. Greig  G. R. Sennefelder  R. Mercaldo-Allen  C. Kuropat  E. Gould  F. P. Thurberg  A. Calabrese 《Estuaries and Coasts》1991,14(3):318-331

In a 3-yr study, late prespawning winter flounder were collected from various stations in Long Island Sound (three of them heavily urbanized) and spawned in the laboratory. For comparative purposes, flounder from two sites in the Boston Harbor area were similarly treated in 1987 and 1988. Of the stations in Long Island Sound, New Haven Harbor alone consistently produced low percent viable hatch and small larvae. Boston Harbor produced the smallest larvae of all sites. There were no significant station-to-station differences in lipid utilization during larval development; yolk reserves at stations showing a low percent viable hatch, small larvae, and low embryonic development rate were probably used in part for stress metabolism. No significant differences in concentrations of polychlorinated biphenyls for collections from Long Island Sound were found either in livers of spawned fish, in sediments, or in eggs of winter flounder. The very low metal concentrations in winter flounder eggs showed no relation to the degree of metal contamination found at stations in Long Island Sound and Boston Harbor.  相似文献   

Creation of an Artificially Produced Fracture Zone to Prevent Contaminated Ground-Water Migration     

Kristen Franz Begor  Michael A. Miller  Rodney W. Sutch 《Ground water》1989,27(1):57-65

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Probabilistic models for ore body recognition     

J. William Miller 《Mathematical Geology》1989,21(5):559-578

Four statistical models have been developed to aid in exploration drilling for ore deposits. The Austinville (Virginia) deposit, which is a Mississippi Valley-type deposit with 31 million metric tons of ore in 17 ore bodies, provides the data base. Because most ore bodies are not solid ore, holes drilled through them will intersect sub-ore mineralization as well as ore. The statistical models were designed to show whether drilling is through an ore body or not, depending on the mineralization intersected by holes. The models are based on a threefold classification of mineralization penetrated by surface drill holes and were developed for cases of fixed budgets with specified number of drill holes and floating budgets with variable number of drill holes. Two classifications were used: (1) binomial ore/non-ore classification and (2) trinomial ore/mineralized/barren. For the fixed budget model with the ore/non-ore classification, at least five holes need to be drilled to decide whether or not an ore body has been penetrated. For the fixed budget model with the ore/mineralized/barren classification, and for both floating budget models, at least three holes need to be drilled. All decisions are based on a 90% confidence level.  相似文献   

Double Glacier Volcano,a ‘new’ Quaternary volcano in the eastern Aleutian volcanic arc     

Bruce L Reed  Marvin A Lanphere  Thomas P Miller 《Bulletin of Volcanology》1992,54(8):631-637

The Double Glacier Volcano (DGV) is a small dome complex of porphyritic hornblende andesite and dacite that is part of the Cook Inlet segment of Quaternary volcanoes of the eastern Aleutian arc. Its discovery reduces the previously described large volcano gap in Cook Inlet segment to a distance similar to that between other volcanoes in the area. DGV lavas are medium-K, calcalkaline andesites and dacites with concentrations of major and minor elements similar to the other Quaternary volcanoes of the Cook Inlet segment. Available K-Ar ages indicate that DGV was active 600–900 ka.  相似文献   

Microphytobenthos: The ecological role of the “secret garden” of unvegetated,shallow-water marine habitats. I. Distribution,abundance and primary production   总被引：1，自引：0，他引：1  

Hugh L. MacIntyre  Richard J. Geider  Douglas C. Miller 《Estuaries and Coasts》1996,19(2):186-201

The microphytobenthos consists of unicellular eukaryotic algae and cyanobacteria that grow within the upper several millimeters of illuminated sediments, typically appearing only as a subtle brownish or greenish shading. The surficial layer of the sediment is a zone of intense microbial and geochemical activity and of considerable physical reworking. In many shallow ecosystems, the biomass of benthic microalgae often exceeds that of the phytoplankton in the overlying waters. Direct comparison of the abundance of benthic and suspended microalgae is complicated by the means used to measure biomass and by the vertical and horizontal distribution of the microphytobenthos in the sediment. Where biomass has been estimated as chlorophyll a, there may be negligible to large (40%) error due to interference by degradation products, except where chlorophyll is measured by high-performance liquid chromatography. The vertical distribution of microphytobenthos, aside from mat-forming species, is determined by the opposing effects of their vertical migration, which tends to concentrate them near the surface, and physical mixing by overlying currents, which tends to cause an even vertical distribution through the mixed layer of sediment. Uncertainties in vertical distribution are compounded by frequently patchy horizontal distribution. Under-sampling on small (<1 m) scales can lead to errors in the estimate that are comparable to the ranges of seasonal and geographic variation. These uncertainties are compounded by biases in the techniques used to estimate production by the microphytobenthos. In most environments studied, biomass (as chlorophyll a) and light availability appear to be the principal determinants of benthic primary production. The effect of variable light intensities on integral production can be described by a functional response curve. When normalized to the chlorophyll content of the surficial sediment, the residual variation in the data described by the functional response curve is due to changes in the chlorophyll-specific response to irradiance. Production by the benthos is often a significant fraction of production in the water column and microphytobenthos may contribute directly to water column production when they are resuspended. Thus on both the basis of biomass and biogeochemical reactivity, benthic microalgae play significant roles in system productivity and trophic dynamics, as well as such habitat characteristics as sediment stability. *** DIRECT SUPPORT *** A01BY074 00003  相似文献