Strength of frozen silt as a function of ice content and dry unit weight     

Francis H. Sayles  David L. Carbee 《Engineering Geology》1981,18(1-4):55-66

A total of 45 unconfined compression tests were conducted on frozen specimens of remolded, saturated Fairbanks silt at dry unit weights ranging from 993 to 1490 kg/m³ with total water contents ranging from 0.28 to 0.58. The rate of strain was 0.005 s⁻¹ . Using the criterion that the ice matrix in the soil fractures at the first point of significant yield shown in the stress-strain curve, which occurs at less than 0.01 strain in this study, the “ice matrix strength” is shown to be nearly proportional to the volumetric ice content of the soil for these tests. The strength at 0.2 strain appears to be nearly independent of the dry unit weight and water content of the soil.  相似文献   

Volatile fatty acid cycling in organic-rich marine sediments     

Francis J. Sansone  Christopher S. Martens 《Geochimica et cosmochimica acta》1982,46(9):1575-1589

Volatile fatty acid (VFA) apparent turnover rates were determined by measuring whole sediment VFA concentrations and the corresponding reaction rate constants. The following ranges of VFA concentrations were measured in Cape Lookout Bight, N.C. sediments (μmole·l_s^?1): acetate 54–660, propionate 1–24, butyrate <0.5–22, iso-butyrate <0.5–6. Apparent turnover rates measured over a one-year period ranged from 18–600 μmole·l_s^?1·h^?1 for acetate and 0.7–7 μmole·l_s^?1·h^?1 for the carboxyl carbon of propionate. Methane production was observed only with acetate and only in sulfatedepleted sediments; total acetate turnover attained approximately the same maximum value in both sulfate-reducing and sulfate-depleted sediments.Apparent turnover rates for acetate and propionate appeared to be controlled by similar factors: in sulfate-reducing (surface) sediments the turnover rates were stimulated by autumn storm-mediated deposition/resuspension events; in deeper sulfate-depleted sediments the turnover rates followed changes in the ambient temperature. Changes in VFA poolsizes were proportionally much larger than changes in corresponding rate constants. The ratio of CO₂ to CH₄ produced from acetate vs. depth suggested that non-methanogenic bacteria accounted for 60% of the acetate turnover in sulfate-depleted sediments.VFA concentrations were much lower in N.C. continental slope mud than in Cape Lookout sediments; acetate was the only VFA detectable throughout the top 40 cm of the slope sediments. The estimated production rate of CO₂ from acetate decreased rapidly with depth. The surface rate was approximately 20 times less than that measured at similar temperatures in sulfate-reducing Cape Lookout sediments.  相似文献   

The recovery of spatial isotope distributions from stepwise degassing data     

Francis Albarède 《Earth and Planetary Science Letters》1978,39(3):387-397

A method for recovering spatial isotope distributions in minerals from stepwise degassing data is presented with special emphasis on rare gas analysis. For a given gas, it requires that one among its isotopes is homogeneously distributed in the system, a condition usually met by those isotopes which are produced by nuclear reaction on major element targets (e.g. ³⁷Ar for argon). This problem is an application of linear inversion techniques, previously developed for geophysical purposes, to the diffusion theory. The calculated solution takes into account experimental inaccuracy of the data and an analysis of their resolving power permits to select the physically meaningful models. An application of the method to the lunar anorthosite 15415 analyzed by Turner [Earth Planet. Sci. Lett. 14 (1972) 169–175] for argon isotopes permits to restore the spatial age distribution in the plagioclase grains and gives a new insight onto the complex history of that rock. Other potential applications are briefly mentioned.  相似文献   

Volcan ceboruco: A major composite volcano of the mexican volcanic belt     

R. S. Thorpe  P. W. Francis 《Bulletin of Volcanology》1975,39(2):201-213

Ceboruco is a major composite volcano at the western end of the Mexican Volcanic Belt, near the junction between the North American and Pacific plates. The volcano is built from successive eruptions of andesite lavas and pyroclastic rocks, and major eruptions during its history have resulted in the formation of two concentric calderas. The youngest volcanic activity has included the extrusion of dacites within the inner caldera and a voluminous flank eruption of andesite during 1870–72. Fumarolic activity persists to the present day. Chemical analyses show that the lavas are of cale-alkaline type and rangs from andesite (SiO₂=58–61%) to acid dacite (SiO₂=68%) in composition. The rate of increase of K₂O relative to SiO is greater than that in volcanic rocks from the Mexican Volcanic Belt as a whole. This indicates that simple models based on the application of such relationships may not be adequate to explain the petrogenesis of calc-alkaline lavas.  相似文献   

The heat flow/heat generation relationship: An interaction model of fluids with cooling intrusions     

Francis Albarede 《Earth and Planetary Science Letters》1975,27(1):73-78

The linear heat flow/heat generation relationship observed for plutonic rocks has been interpreted by Lachenbruch as requiring an exponential depletion of radioactive elements with depth. The exponential depletion is difficult to interpret in terms of fractional crystallization of cooling magmas. Geochemical investigations and autoradiographic method have shown that an important part of the radioactive elements are in leachable sites in the rocks. A model is proposed in which the redistribution of these elements is achieved by fluid-rock interaction during the crystallisation and subsequent cooling of intrusions. A dissolution-precipitation process, mathematically similar to multipass zone refining will result in an exponential distribution of radioactive elements. The geothermal and geochemical implications of the model are discussed.  相似文献   

Note préliminaire concernant la genèse du gisement de mercure d'Almadén     

Francis Saupé 《Mineralium Deposita》1967,2(1):26-33

Résumé L'absence de minéralisation du Hg dans les failles, ainsi que l'identité de la minéralisation de part et d'autre de dykes intrusifs sécants postérieurs à la minéralisation et traversant le gisement d'Almadén, mettent en doute l'hypothèse d'une minéralisation épigénétique, telle qu'elle a été admise jusqu'à présent. — La liaison stratigraphique à trois horizons de quartzite bien déterminés et surtout l'observation de grains de cinabre entre le cur de grains siliceux détritiques et leur écorce d'accroissement démontrent une origine du cinabre antérieure à la silicification des grains de quartz, que l'on peut admettre comme diagénétique. — La coïncidence spatiale et temporelle du volcanisme gothlandien et de la minéralisation mercurifère laissent à supposer un lien génétique entre les deux.

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The absence of Hg-mineralization in the faults, as well as the identity of mineralization on both sides of cross-cutting post-mineralization intrusive dykes speak against the hypothesis of an epigenetic mineralization which has been postulated so far. — The stratigraphic linkage to three well defined quartzite horizons and especially the microscopical observation of cinnabar grains included between the detritic core of quartz grains and the secondary silica overgrowth, demonstrate that the origin of cinnabarite is anterior to the silicification of the quartz grains, which can be admitted as diagenetic. — The overlap in space as well as in time of the gothlandian volcanism and the Hg-mineralization lead to suppose a genetical relationship between both.

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Bedding in Scottish (Fifeshire) Tuff-pipes and its relevance to maars and calderas     

E. H. Francis 《Bulletin of Volcanology》1970,34(3):697-712

Along the coast between Lower Largo and St. Monance, in Fife, Scotland, Carboniferous sediments are piecerd by 13 exceptionally well-exposed basaltic tuff-pipes. The pyroclastic rocks, which are bedded in either centroclinal or collapsed form, were originally formed subaerially. They are separated by ring faults from the surrounding sediments which are turned down against the pipe margins. The tuffs in the pipes have undergone cauldron subsidence of at least 500 m. Clastic and magmatic minor intrusions, particularly at the margins of the pipes, accompanied the subsidence. As comparable amounts of subsidence are recorded in many basaltic tuffpipes (some with, others without ring fractures) in other parts of the world, it is suggested that subsidence may have contributed to the formation of maars. Comparison is made between cauldron-subsidence features in tuff-pipes and those of calderas.  相似文献   

A simple model for the diurnal variation of the mixing depth and transport flow     

Francis S. Binkowski 《Boundary-Layer Meteorology》1983,27(3):217-236

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The Triassic of the southern margin of the Tethys in the Levant and its correlation across the Jordan Rift Valley     

Dr. Yehezkel Druckman  Dr. Francis Hirsch  Dr. Tuvia Weissbrod 《International Journal of Earth Sciences》1982,71(3):919-936

The Triassic of the Levantine region consists of four sedimentary cycles: I. Scythian — Lower Anisian; II. Early Upper Anisian; III. Late Upper Anisian — Carnian; IV. Late Carnian — Norian.Regional biofacial affinities point to the existance of a western Tethyan Werfen facies (cycle I), a sephardic biofacies (cycles II and III) and a rather alpinotype platform facies (cycle IV). A correlation across the Jordan Rift Valley is suggested, primarily based on bio- and lithostratigraphic evidence of the Permo-Triassic rocks. The stratigraphic implications of this correlation support the existance of a left lateral strike slip along the Jordan Rift Valley.

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Zusammenfassung Die Trias im Levant ist in vier Sedimentationszyklen gegliedert: I. Skythian — Unteres Anisian; II. Oberes Anisian; III. Oberes Anisian — Karnian; IV. Oberes Karman — Norian.Die regionalen Faziesbeziehungen deuten auf das Vorhandensein einer Westtethyalen Werfener Fazies (Zyklus I), einer West- und Südtethyalen Sephardischen Fazies (Zyklen II und III) und einer eher alpinotypischen Plattformfazies (Zyklus IV).Eine Korrelation der permisehen und untertriadischen Gesteine auf beiden Seiten des Jordantales wird vorgeschlagen. Die stratigraphischen Folgerungen dieser Korrelation unterstützen die Existenz einer linken Transversalverschiebung entlang des Jordantal Rifts.

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Résumé Le Trias du Levant comprend quatre cycles sédimentaires: I. Scythien-Anisien inférieur; II. Anisien supérieur; III. Anisien supérieur — Carnien; IV. Carnien supérieur — Norien.La succession des biofaciès débute par le faciès Werfénien, qui englobait pratiquement la Téthys occidentale éotriasique toute entière (cycle I). Dans le courant du Mésotrias, le faciès Sépharade s'étend aux marges méridionales et occidentales de la Téthys (cycles II et III), tandis qu'un faciès de plateforme d'affinité plutôt alpine représente le Trias terminal (cycle IV).Une corrélation des séries Permo-Eotriasiques du Néguev et de Transjordanie est proposée. Les implications stratigraphiques de cette corrélation appuient l'existence d'un coulissage sénestre tout au long du Rift de la vallée du Jourdain.

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Feeding habits of age-0 striped bass,<Emphasis Type="Italic">Morone saxatilis</Emphasis>, in the mid-Hudson River estuary: Temporal,spatial, and ontogenetic variation     

Rebecca?C.?JordanEmail author  David?V.?Howe  Thomas?P.?Hurst  Francis?Juanes 《Estuaries and Coasts》2003,26(6):1486-1493

We quantified temporal and spatial variability in diets of 950 juvenile (age-0) striped bass in the Hudson River estuary. We used canonical correspondence analysis to assess the roles of temporal and spatial habitat variability in juvenile diet variation. We found that juvenile striped bass diets in the Hudson River were only modestly comparable to diets in other east coast estuaries. Among-year differences (51.4%) and spatial differences (41.9%) were substantially associated with juvenile striped bass diet. We found ontogeny (2.8%) and within-season variation (9.5%) to only weakly associate with diet variation. Our results indicate that an understanding of the temporal and spatial variation within the Hudson River estuary is vital in understanding variation in feeding by resident juvenile fish.  相似文献