Compositional variability of Glacier Peak tephra and its stratigraphic significance

1978 ◽  
Vol 15 (10) ◽  
pp. 1554-1567 ◽  
Author(s):  
J. A. Westgate ◽  
M. E. Evans
Keyword(s):  
National Park ◽  
Western Montana ◽  
Violent Event ◽  
Age Composition ◽  
Relative Age ◽  
Palaeomagnetic Data ◽  
Tephra Layers ◽  
Compositional Variability ◽  
Northern Idaho ◽  
Eastern Washington

Glacier Peak Volcano erupted many times during the period from ~11 000 to ~13 000 years ago and produced at least Three widespread tephra layers that serve as valuable stratigraphic markers in northwestern United States and the adjacent plains of southwestern Canada. Each of these units can be recognized by their stratigraphic, petrographic, and chemical attributes.Tephra was shed over eastern Washington, northern Idaho, western Montana, and southernmost Alberta during each of the eruptions responsible for the older two units; the other layer was deposited during the youngest and most violent event that directed tephra to the southeast as far as Yellowstone National Park, ~950 km from the volcano.Chemical data on glass, hornblende, hypersthene, feldspar, magnetite, and ilmenite show a systematic and unidirectional trend in tephra composition with age; earlier eruptions produced slightly more acidic tephra. This age–composition relationship is confirmed by palaeomagnetic data obtained from 116 specimens collected from two 5 m thick sections. It should therefore be possible to determine the relative age of Glacier Peak tephra samples by their composition alone.The chronology of the Glacier Peak eruptive sequence is still poorly understood. This is especially true of the oldest unit which has so far only been found in southeastern Alberta. Proximal occurrences should be sought in the bogs of eastern Washington where prospects of preservation and age definition are optimised.

Clonal diversity within and among introduced populations of the apomictic vine Bryonia alba (Cucurbitaceae)

2000 ◽  
Vol 78 (11) ◽  
pp. 1469-1481 ◽  
Author(s):  
Stephen J Novak ◽  
Richard N Mack
Keyword(s):  
United States ◽  
Clonal Diversity ◽  
Western Montana ◽  
Western United States ◽  
Single Population ◽  
Multiple Introductions ◽  
Introduced Populations ◽  
Northern Utah ◽  
Northern Idaho ◽  
Eastern Washington

Bryonia alba L. (Cucurbitaceae) is a herbaceous Eurasian vine that predominantly reproduces clonally (asexually) through apomixis. We assessed the magnitude and distribution of clonal diversity within and among 23 recently established populations of B. alba in its new range in the western United States, based on the distribution of multilocus isozyme genotypes. Fifty-two unique clones were detected: 30 in the nine populations from eastern Washington and northern Idaho, and the remaining 22 in 14 populations from western Montana, northern Utah, and southern Idaho. On average, each population of B. alba was composed of 6.4 clones, and the proportion of distinguishable clones was 0.275. Multilocus diversity (D) was 0.632 and multilocus evenness (E) was 0.556. Twenty-six of 52 clones (50%) were restricted to a single population, and, on average, each clone occurred in 2.83 populations. Compared with other clonally reproducing plant species, this vine possesses moderate to high levels of clonal diversity in its new range in the western United States. This diversity appears to be a consequence of the events associated with its introduction (including multiple introductions), founder effects, and the proportion of sexual to apomictic reproduction within populations.Key words: invasive vine, apomixis, multilocus genotypes, clonal diversity and evenness, Bryonia alba, Cucurbitaceae.

Age, distribution, and stratigraphy of Glacier Peak tephra in eastern Washington and western Montana, United States

1993 ◽  
Vol 30 (3) ◽  
pp. 535-552 ◽  
Author(s):  
Franklin F. Foit Jr. ◽  
Peter J. Mehringer Jr. ◽  
John C. Sheppard
Keyword(s):  
Radiocarbon Dating ◽  
Age Distribution ◽  
Analytical Techniques ◽  
Western Montana ◽  
East Central ◽  
Tephra Layers ◽  
Tephra Stratigraphy ◽  
Mineral Compositions ◽  
Eastern Washington ◽  
Lake Deposits

Tephra layers from Williams Lake Fen, Wildcat Lake, and East Wenatchee, Washington, and Kearns Basin, Lost Trail Pass, Sheep Mountain Bog, and Marys Frog Pond, Montana, were analyzed by electron microprobe (EMP), and associated lake deposits were radiocarbon dated. Though the tephra layers can be grouped by source (Glacier Peak, Mount Mazama, Mount Saint Helens, and unknown source), statistical analyses of both glass and mineral compositions show that finer distinctions within a group (for example, Glacier Peak B, M, and G) cannot be made on the basis of chemical data obtained using conventional EMP techniques. It appears that more-sensitive analytical techniques may be needed to discriminate among the Glacier Peak tephras. Tephra stratigraphy at the various sites reveals a potentially greater complexity in Glacier Peak tephra distributions and ages than was anticipated. All sites, except Sheep Mountain Bog and East Wenatchee, contained two Glacier Peak tephras. Taken as a whole the Glacier Peak tephra layers may record closely timed, multiple eruptions with restricted ash falls as well as widespread tephra from large eruptions. Radiocarbon dating generally confirms a 14C age of 11 200 years BP for a distal Glacier Peak couplet(s) that occurs, stratigraphically, both above and below Mount Saint Helens J tephra in east-central Washington.

Geographic structure of sibling species and cytotypes of the Simulium arcticum complex (Diptera: Simuliidae) in rivers of central Idaho and southeastern Washington, United States of America

2018 ◽  
Vol 150 (3) ◽  
pp. 366-377 ◽  
Author(s):  
Gerald F. Shields ◽  
John P. Shields
Keyword(s):  
United States ◽  
Sibling Species ◽  
United States Of America ◽  
Polytene Chromosomes ◽  
Sensu Stricto ◽  
Western Montana ◽  
Geographic Structure ◽  
Northern Idaho ◽  
Eastern Washington ◽  
Central Idaho

AbstractWe made 37 collections and analysed the polytene chromosomes of salivary glands of 726 larvae of the Simulium arcticum Malloch (Diptera: Simuliidae) complex from 10 locations in an unstudied region from central Idaho and southeastern Washington, United States of America. We compared our results to previous population cytotaxonomic research on larvae of this complex from western Montana, northern Idaho, and eastern Washington, United States of America. We identified four sibling species, S. brevicercum Knowlton and Rowe, S. saxosum Adler, S. arcticum sensu stricto, S. apricarium Adler, Currie, and Wood; and three cytotypes, S. arcticum IIL-9, IIL-17, and IIL-79, previously described by us. We discovered a new cytotype, S. arcticum IIL-80, at three locations in the western region of our sample area. We also found combinational (ancestral) types between S. saxosum and S. arcticum sensu stricto and between S. saxosum and S. arcticum IIL-79, suggesting that ancestral populations of the complex still exist. Geographic structuring of these sibling species and cytotypes are documented given that S. saxosum occurred in western regions, S. arcticum IIL-79 in northeastern regions, and S. apricarium in southeastern regions of our study area.

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