Glaciation of Chagvan Bay Area, Southwestern Alaska

Morphologic and stratigraphic evidence in this area indicates that a four-fold succession of glaciers originating in the Ahklun Mountains, spread over the coastal lowlands as broad piedmont lobes. The Kemuk and Clara Creek glaciations are considered Pre-Wisconsin, the Chagvan and Unaluk glaciations Wisconsin in age. Radiocarbon dates for the Unavuk and Chagvan drifts are 8910 ± 110 yr and >45,000 yr respectively. A broad bedrock channel buried beneath unconsolidated preglacial and glacial sediments was cut when relative sea level was 200 ft below its present level. Relationships of sedimentary fills to this and to a younger buried channel point to late Tertiary submergence of the Bering Shelf followed by eustatic changes related to fluctuations of Pleistocene glaciers.Au voisinage de la baie Chagvan, les indices morphologiques et stratigraphiques révèlent qu'à au moins quatre reprises, des glaciers descendus des monts Ahklun se sont répandus sur les basses-terres côtières en formant de larges lobes de piedmont. La plus ancienne moraine, déposée au cours de la glaciation de Kemuk, est profondément altérée et complètement recouverte par de la moraine plus récente. Les berges morainiques massives de la glaciation de Clara Creek, la seconde en âge et la plus étendue des avancées glaciaires, ont été grandement modifiées par l'érosion et les mouvements de masse, mais les sédiments qui les composent sont moins altérés que ceux de la moraine de Kemuk. Les moraines construites durant les glaciations moins étendues de Chagvan et d'Unaluk montrent une topographie moins modifiée, caractérisée par des crêtes basses et arquées et de nombreux lacs de fonte (Kettle) : les datations au radiocarbone assignent un âge minimum de 8910 ± 110 ans à la moraine d'Unaluk et de plus de 45,000 à la moraine de Chagvan.Un large chenal, enfoui sous des sédiments préglaciaires et glaciaires non-consolidés, a été creusé dans la roche en glace à une époque où le niveau de la mer se trouvait à 200 pieds (60 m) ou plus sous le niveau actuel. Les rapports entre, d'une part, les remblaiements sédimentaires et, d'autre part, ce chenal et un autre chenal fossile plus récent indiquent une submergence finitertiaire de la plateforme de Béring, suivie de changements eustatiques liés aux fluctuations des glaciers pléistocènes

Mineralogical Variations within Two Widespread Holocene Tephra Layers from Cascade Range Volcanoes, U.S.A.

The heavy mineral content of volcanic ash from Mount Mazama (layer O) and Mount St. Helens (layer Yn) decreases downwind from each volcano. The transparent heavy mineral suite of layer O also varies downwind because of differences in specific gravity and shape of the grains, reflecting sorting processes during transportation in the atmosphere. In the first few tens of kilometers from the volcano some values strongly deviate from the general trend. This is attributed to exceptional turbulence at the time of eruptions in the vicinity of the vent.Le contenu en minéraux denses a été étudié dans des échantillons provenant de deux retombées volcaniques largement répandues sur le nord-ouest des États-Unis et sur le sud-ouest du Canada. L'une d'entre elles correspond à l'explosion du mont Mazama (Oregon) survenue il y a environ 6700 ans; elle est connue sous le nom de « couche O ». L'autre résulte d'une explosion du mont St. Helens qui a eu lieu il y a environ 3400 ans; elle est connue sous le nom de « couche Yn ». Dans chacun des deux lobes, le contenu en minéraux denses diminue avec la distance aux volcans respectifs, et des variations spatiales systématiques de l'association de minéraux denses transparents dans le lobe de la « couche O » ont été mises en évidence. Ces variations sont comparées à celles qui ont été observées dans les retombées récentes des volcans mont St. Helens (É.-U., 18 mai 1980) et El Chichôn (Mexique, mars-avril 1982). Elles sont expliquées par des processus de sélection qui ont lieu dans les nuages de poussières au cours du transport dans l'atmosphère.In Proben, die aus zwei ausgedehnten vulkanischen Niederschlàgen im Nord-Westen der U.S.A. und dem Sùd-Westen Kanadas stammen, wurde der Gehalt an dichten Mineralen studiert. Der eine Niederschlag entspricht dem Ausbruch des Mount Mazama (Oregon), der vor etwa 6700 Jahren stattgefunden hat; er ist unter der Bezeichnung "Schicht O" bekannt. Der andere entstammt einem Ausbruch des Mount St. Helens, der vor ungefàhr 3400 Jahren stattgefunden hat ; er ist unter der Bezeichnung "Schicht Yn" bekannt. In jedem der zwei Ausschnitte nimmt der Gehalt an dichten Mineralen ab, entsprechend zur Entfernung zum jeweiligen Vulkan, und im Ausschnitt der "Schicht O" konnten systematische ôrtliche Schwankungen in der Assoziation der transparenten dichten Minérale nachgewiesen werden. Dièse Schwankungen werden verglichen mit denen, die in den neueren Niederschlagen der Vulkane von Mount St. Helens (U.S.A., 18. Mai 1980) und El Chichôn (Mexiko, Màrz-April 1982) beobachtet wurden. Sie werden erklàrt durch Selektionsprozesse, die in den Staubwolken wàhrend des Transports in der Atmosphère stattgefunden haben

Assessing Learning-Centered Leadership: Connections to Research, Professional Standards, and Current Practices

Describes an assessment model designed to evaluate school leaders' performance. Unlike existing tools, this new system will assess both individuals and teams, and focuses specifically on instructional leadership and behaviors that improve learning

Temperature, Activity and Lizard Life Histories

Lizard life-history characteristics vary widely among species and populations. Most authors seek adaptive or phylogenetic explanations for life-history patterns, which are usually presumed to reflect genetic differences. However, lizard life histories are often phenotypically plastic, varying in response to temperature, food availability, and other environmental factors. Despite the importance of temperature to lizard ecology and physiology, its effects on life histories have received relatively little attention. We present a theoretical model predicting the proximate consequences of the thermal environment for lizard life histories. Temperature, by affecting activity times, can cause variation in annual survival rate and fecundity, leading to a negative correlation between survival rate and fecundity among populations in different thermal environments. Thus, physiological and evolutionary models predict the same qualitative pattern of life-history variation in lizards. We tested our model with published life-history data from field studies of the lizard Sceloporus undulatus, using climate and geographical data to reconstruct estimated annual activity seasons. Among populations, annual activity times were negatively correlated with annual survival rate and positively correlated with fecundity. Proximate effects of temperature may confound comparative analyses of lizard life-history variation and should be included in future evolutionary models

A Deep Multicolor Survey I. Imaging Observations and Catalog of Stellar Objects

We have used the KPNO 4-meter Mayall telescope to image 0.83 square degrees of sky in six fields at high galactic latitude in six filters spanning 3000-10000\AA\ to magnitude limits ranging from 22.1 to 23.8. We have assembled a catalog of 21,375 stellar objects detected in the fields for use primarily in conducting a multicolor search for quasars. This paper describes the data reduction techniques used on the CCD data, the methods used to construct the stellar object catalog, and the simulations performed to understand its completeness and contamination.Comment: To Appear in ApJ Supplement, 1996. 168k uuencoded gunzipped tarred tex file (requires aas2pp4.sty and tighten.sty) and 4 PostScript figures. Also available at http://astro.as.arizona.edu/~pathall/astro.html#preprint

The Little Ice Age: glacier variations and climate since AD 1250 [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): During the past hundred years, mountain glaciers throughout the world have retreated significantly from moraines built during the previous several centuries. In the 1930s, Francois Matthes of the U.S. Geological Survey concluded that the moraines represent the greatest advances of glaciers since the end of the last glacial age, some 10,000 years earlier, and informally referred to this late Holocene interval of expanded ice cover as the Little Ice Age

Ariel - Volume 2 Number 7

Editors Richard J. Bonanno Robin A. Edwards Associate Editors Steven Ager Stephen Flynn Shep Dickman Tom Williams Lay-out Editor Eugenia Miller Contributing Editors Michael J. Blecker W. Cherry Light James J. Nocon Lynne Porter Editors Emeritus Delvyn C. Case, Jr. Paul M. Fernhof

Organizing the innovation process : complementarities in innovation networking

This paper contributes to the developing literature on complementarities in organizational design. We test for the existence of complementarities in the use of external networking between stages of the innovation process in a sample of UK and German manufacturing plants. Our evidence suggests some differences between the UK and Germany in terms of the optimal combination of innovation activities in which to implement external networking. Broadly, there is more evidence of complementarities in the case of Germany, with the exception of the product engineering stage. By contrast, the UK exhibits generally strong evidence of substitutability in external networking in different stages, except between the identification of new products and product design and development stages. These findings suggest that previous studies indicating strong complementarity between internal and external knowledge sources have provided only part of the picture of the strategic dilemmas facing firms