Late Quaternary mollusks from glacial Lake Algonquin,Nipissing, and transitional sediments from southwestern Ontario,Canada

Mollusks were studied from six sites in Lake Algonquin deposits (12,000-10,000 yr B.P.), five transitional (Lake Stanley low stage; 10,000 – 6000 yr B.P.), and six Nipissing stage sites (6000-4000 yr B.P.) east of Lake Huron in southwestern Ontario. The sites represent a variety of near-shore, lagoonal, estuarine, and fluvial environments. Eighteen species were limited to occurrences in Algonquin stage deposits; 8 were found only in the transitional age sites; and 14 species were restricted to Nipissing stage localities. With the possible exception of Goniobasis livescens, which occurred at five of the six Nipissing stage sites, the remaining stratigraphically limited species were usually restricted to one or two localities and probably cannot be used as zone fossils. Some cold-tolerant species (e.g., Anodonta grandis simpsoniana) were very early migrants into the study area, while others arrived later, apparently from eastern, southern, and western sources. Mollusks proved useful in paleoenvironmental reconstructions and to a lesser extent in biostratigraphic zonation.     

The peak harmonic response of locally non-linear systems

This paper presents an approximate analytical technique for determining the steady-state response of a class of systems with spatially localized non-linearity. A method of finding the amplitude peaks in various modes is presented. Numerical examples illustrate the nature and accuracy of the results of the approximate analysis.     

Kinetics and thermochemistry of amyl xanthate adsorption by pyrite and marcasite

The kinetics and thermochemistry of the xanthate adsorption reaction on pyrite and marcasite were evaluated with respect to the existing theory. The rate of xanthate adsorption was studied in a stirred reactor and the xanthate concentration was determined by UV spectrophotometry as a function of time. The heat of the adsorption reaction was measured with a microcalorimeter. The results from both experiments indicate that xanthate adsorption by pyrite or marcasite involves the formation of dixanthogen by an electrochemical reaction at the solid surface which supports the conclusions of other investigators:

$\text{1}\text{2}\text{O}{}_2\text{(aq) =}\text{1}\text{2}\text{O}{}_2\text{(ad) 2X + 2H}{}^{\mathrm{+}}\text{+}\text{1}\text{2}\text{O}{}_2\text{→ X}{}_2\text{(ad) + H}{}_2\text{O}$

The rate of the adsorption reaction was found to be approximately one-half order with respect to the xanthate concentration and to have an activation energy of 7.5 kcal/mole. Additionally, the rate was found to have a slight dependence on pH under certain conditions. In view of these results, it appears that the adsorption reaction is controlled by electrochemical discharge at the pyrite surface. Analysis of the data in terms of an electrochemical kinetic model successfully explained the observed rate phenomena.The measured heat of the adsorption reaction at low pH was found to be between ?63 and ?56 kcal/mole of adsorbed dixanthogen and independent of surface coverage. These experimental heats of adsorption agree with the value of ?57 kcal/mole of dixanthogen calculated for the oxidation of xanthate by oxygen from thermodynamic data reported in the literature.     

Kleintektonische Untersuchungen in der Umgebung der Station „General Bernardo O'Higgins“ Nordwestspitze der antarktischen Halbinsel

Zusammenfassung In der unmittelbaren Umgebung der chilenischen Antarktisstation General Bernardo O'Higgins sind die klastischen Sedimente kretazischen Alters innerhalb der alpidischen Orogenese nach drei verschiedenen Verformungsplänen gefaltet worden. Die B₁Achsen sind die ältesten und entsprechen mit ihrem ENE-Streichen dem Großbau der Nordspitze Grahamlands. B₂ streicht etwa 168°, B₃ rund 30^o.

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In the immediate surroundings of the Chilean Station General Bernardo O'Higgins, the clastic sediments of Cretaceous age have been folded according to three different systems of deformation, during the alpine (Cretaceous-Tertiary) orogeny. The B₁ axes are the oldest ones, and their strike ENE corresponds to the general structures of northern Grahamland. B₂ strikes N 12° W approximately and B₃ roughly N 30° E.

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Resumen En los alrededores inmediatos de la Base antártica chilena General Bernardo O'Higgins los sedimentos clásticos del Cretácico han sido plegados según tres diferentes sistemas de deformación durante la orogénesis alpídica. Los ejes B₁ son los más antiguos y su rumbo ENE corresponde a la estructura general de la parte Norte de la Tierra de Graham. B₂ tiene rumbo N 12° W aproximadamente, B₃ alrededor de N 30° E.

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Résumé Aux alentours de la Station chilienne Général Bernardo O'Higgins, les sédiments clastiques du Crétacé ont été plissés selon trois différents systèmes de déformation pendant l'orogénèse alpine (Cretacique-Tertiaire). Les axes B₁ sont les plus anciens, et leur direction ENE correspond à la structure générale de la partie Nord de la Terre de Graham. B₂ a une direction approximative de N 12° W, et B₃ de N 30° E environ.

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General Bernardo O'Higgins , .

     

Chemical weathering and related controls on surface water chemistry in the Absaroka Mountains,Wyoming

Chemical relationships among surface waters, soils and rocks were investigated in the drainage basin of the North Fork of the Shoshone River in northwestern Wyoming. The area is underlain entirely by andesitic volcanic rocks. Smectite is the only clay mineral forming in soils over much of the area, although minor kaolinite occurs in a few areas of higher-than-average rainfall.Mass-balance calculations relating stream water chemistry to rock alteration indicate that controls on the chemistry of surface waters take place not in the soil zone but in the altered rock zone. The dominant weathering process which controls the water chemistry is slight alteration of large volumes of rock, rather than development of chemical equilibria involving secondary phases in the soil zone. The altered rock is enriched in feldspars and depleted in ferromagnesian minerals compared to fresh rock. The high rate of physical erosion of the area is enough to remove the residue, reexpose the bedrock, and continue the weathering process.     

The organic geochemistry of black sedimentary barite: significance and implications of trapped fatty acids

Fatty acids isolated in sedimentary black barite (BaSO₄) from Arkansas and Nevada were identified by gas chromatography-mass spectroscopy. The dominant or major fatty acids found in these beds of barite are C_16:0, C_18:0, and C_18:1. The occurrence and distribution of these acids in this type of rock may serve as “molecular fingerprints” of microbial biogeochemical processes. The organic matter and associated microorganisms are shown to be trapped within the finely crystalline barite, thus forming a closed system for microbial diagenesis.Important differences that occur in the distribution of the lesser or minor fatty acids probably result from: (1) the nature of the progenitor organic detritus in the environment of barite deposition: and (2) the subsequent degree of microbiological alteration of the parent organic debris swept into and trapped in the depositional environment.Three general models of sedimentary environments are proposed in which anoxic conditions may prevail and where barium sulfate (BaSO₄) may precipitate: (1) in a silled basin with semi-restricted circulation; (2) on an outer continental shelf where the slope is encroached upon by water of the oxygen minimum layer; (3) on a low-energy, inner shelf or semi-restricted embayment impinged by a wedge of anoxic water.The major geochemical and geological parameters which are believed to be the significant factors controlling the formation and high grade of these organic-rich, black bedded barites are: (1) a unique source of barium-rich fluid that only contains trace amounts of other elements; (2) the presence of an anoxic bottom environment within the depositional basin; (3) a reflux source of sulfate ion; (4) an adequate source of organic matter.The results of this study may serve as guidelines for future exploration in similar, untested sedimentary basins, especially those with rocks of middle Paleozoic age.     

Workshop on Indices and Indicators for Climate Extremes, Asheville, NC, USA, 3–6 June 1997 Breakout Group C: Temperature Indices for Climate Extremes

The "temperature" breakout group at the 1997 Asheville Workshop on Indicators and Indices for Climate Extremes reviewed and developed the rationale for a choice of temperature indices for monitoring changes in climate extremes, and the supporting data required. A set of basic and supplementary key indices was drawn up. The key indices are meant to be easy to interpret, be relevant to the practical concerns of policy makers and others in the public sector and provide potential inputs into the Third Assessment Review of the Intergovernmental Panel on Climate Change that is expected to report in 2001. The indices are expressed in various ways to facilitate spatial and temporal trend detection and impact analysis. There is flexibility in the number and the form of the indices identified and the choice for any particular application is subject to further analysis and prioritization. The success of this endeavor will depend on original work being done to further develop the indices and on the cooperation of organizations globally to provide the data necessary for the development and the implementation of the indices. This paper summarizes the group's recommendations.