Mount Churchill, Alaska: source of the late Holocene White River Ash

1995 ◽  
Vol 32 (6) ◽  
pp. 741-748 ◽  
Author(s):  
D. H. Richter ◽  
S. J. Preece ◽  
R. G. Mcgimsey ◽  
J. A. Westgate
Keyword(s):  
Late Holocene ◽  
Laboratory Data ◽  
Summit Crater ◽  
Distribution Patterns ◽  
Common Source ◽  
White River ◽  
Rock Fragments ◽  
Summit Area ◽  
South Central ◽  
Glass Compositions

Although the White River Ash was first recognized by F. Schwatka in 1883, the source of this widespread bilobate Plinian deposit in northwestern Canada and adjoining eastern Alaska has not been definitively identified. Recent investigations disclose that Mount Churchill, in the St. Elias Mountains of south-central Alaska, contains a summit crater whose rim is chiefly composed of ash, coarse pumice, and exotic rock fragments. The pumice clasts decrease in size and the exotic rock fragments disappear with increasing distance from the summit area. Pumice from the Mount Churchill summit, and from the White River Ash deposits up to 25 km from the summit area, are mineralogically and chemically similar. Microprobe analyses of the summit pumice glass are virtually identical to those of more distant proximal White River Ash glass. Fe–Ti oxide compositions in the Mount Churchill proximal tephra indicate that all tephra sampled during this study is from the younger, eastern lobe of the White River Ash. These field and laboratory data demonstrate that Mount Churchill is a Holocene volcano and the source of the eastern lobe of the White River Ash. Glass compositions and distribution patterns, however, indicate both lobes of the ash have a common source.

scholarly journals Epidemiology of carbapenem-resistant Enterobacteriaceae in a Tertiary Care Center in the Kingdom of Bahrain

2019 ◽  
Vol 11 (02) ◽  
pp. 111-117 ◽  
Author(s):  
Nermin Kamal Saeed ◽  
Safaa Alkhawaja ◽  
Nashawa Fawzy Abd El Moez Azam ◽  
Khalil Alaradi ◽  
Mohammed Al-Biltagi
Keyword(s):  
Control Measure ◽  
Care Center ◽  
Tertiary Care ◽  
Laboratory Data ◽  
Control Measures ◽  
Clinical Samples ◽  
Common Source ◽  
Care Hospital ◽  
Carbapenem Resistant ◽  
Carbapenem Resistant Enterobacteriaceae

Abstract PURPOSE: The purpose of the study is to estimate the rate of infection with carbapenem-resistant Enterobacteriaceae (CRE) in the main governmental tertiary care hospital in Bahrain. MATERIALS AND METHODS: All clinical samples with positive growth of CRE over 6-year period (January 2012–December 2017) were collected from the microbiology laboratory data. RESULTS: The CRE incidence was high in the first half of study period (2012–2014) and then decreased between 2015 and 2017, after implementation of intensified CRE control measure bundle. About 49.4% of CRE-positive samples were isolated from the elderly age group (above 65 years old), most of them were admitted in the intensive care unit (ICU). The most common isolated organisms were Klebsiella pneumoniae (87.0%), followed by Escherichia coli (7.9%). Isolates from deep tracheal aspirate and midstream urine specimens were the most common source of CRE isolates (27.3%) and (26.3%), respectively. Bacteremia was documented in 21.2% of cases. CRE isolates in the study showed high rates of resistance to aminoglycosides (72.2% resistant to amikacin and 67.3% to gentamicin). Alternatively, most isolates retained their susceptibility to colistin and tigecycline with sensitivity of 83.9% and 85.7%, respectively. Combined resistance to both colistin and tigecycline was observed in 0.06% of total isolates. CONCLUSION: Elderly population and ICU admission were important risk factors for CRE acquisition. Most of CRE isolates were sensitive to both colistin and tigecycline, which make them the best combination for empiric frontline therapy for suspected serious CRE infection in our facility. Implementing CRE-bundled infection control measures significantly reduced the incidence of CRE infection in our hospital.

Alluvial fan depositional records from north and south-facing catchments in semi-arid montane terrain

2017 ◽  
Vol 89 (1) ◽  
pp. 237-253 ◽  
Author(s):  
Michael J. Poulos ◽  
Jennifer L. Pierce
Keyword(s):  
Late Holocene ◽  
Source Area ◽  
Alluvial Fan ◽  
Potential Bias ◽  
Landform Evolution ◽  
Sediment Yields ◽  
Erosion Rates ◽  
South Central ◽  
Valley Incision ◽  
North And South

AbstractValley asymmetry reflects differences in landform evolution with aspect; however, few studies assess rates and timing of asymmetric erosion. In south-central Idaho, we combine alluvial fan volume reconstructions with radiocarbon deposit dating to compare the source-catchment normalized fan deposition rates of catchments incised into north (n=5) and south-facing (n=3) valleys, which differ during the late Holocene from 7.7 to 10.1 mm/ka, respectively, but are not significantly different. South-facing catchments produced 1.3× more fan sediment per unit source-area during the late Holocene, whereas over the last 10 Ma they have evolved to be 2.1× larger with 2.8× greater eroded volumes and 7.6° gentler slopes (24.5° versus 32.1°, average). Late Holocene differences in sediment yields with aspect cannot fully explain differences in landforms. Potential bias in sediment deposition and/or remobilization cannot fully explain the similarity of erosion rates during the late Holocene. Valley asymmetry appears to have developed primarily during different conditions. While valley asymmetry development may be quicker during glacial climates, development is likely accelerated early in a valley’s history, such as during initial valley incision, because asymmetric degradation serves as a negative feedback that reduces aspect-related differences in erosion and drives valleys towards steady state.

Mid- to Late Holocene shoreline reconstruction and human occupation in Ancient Eretria (South Central Euboea, Greece)

Geomorphology ◽  
2014 ◽  
Vol 208 ◽  
pp. 225-237 ◽  
Author(s):  
Matthieu Ghilardi ◽  
David Psomiadis ◽  
Kosmas Pavlopoulos ◽  
Sylvie Müller Çelka ◽  
Sylvian Fachard ◽  
...  
Keyword(s):  
Late Holocene ◽  
Human Occupation ◽  
South Central

The effects of source and destination on growth and metal uptake in freshwater clams reciprocally transplanted among south central Ontario lakes

1989 ◽  
Vol 67 (4) ◽  
pp. 855-863 ◽  
Author(s):  
Scott G. Hinch ◽  
Roger H. Green
Keyword(s):  
Metal Uptake ◽  
Soft Tissues ◽  
Common Source ◽  
Transplant Experiment ◽  
Reciprocal Transplant Experiment ◽  
Post Transplant ◽  
Elliptio Complanata ◽  
South Central ◽  
Freshwater Clams ◽  
Strong Source

The relative contributions of genotype and environment to growth and metal uptake in freshwater unionid clams (Elliptio complanata) were evaluated using a reciprocal transplant experiment. In August 1985, comparable sites were selected in three south central Ontario lakes with alkalinities of 22, 153, and 238 μequiv.∙L−1. Shell length, height, and width varied in a manner that could not be related to lake alkalinities. There were differences among the clam populations in allelic frequencies (at the Pgm and Lap-2 loci). Clams were marked, measured, and reciprocally transplanted among the three lakes. In August 1986, marked individuals were recovered, remeasured, and analysed for levels of Cu, Zn, Mn, and Cd in soft tissues. The transplant source had a strong influence on clam growth during the post-transplant year. This source effect may result from genetic differences among the populations. Tissue metal concentrations at the end of the post-transplant year were a function of both source and destination. The use of freshwater clams as transplant biomonitors must be reassessed since there is a strong source component to growth and metal uptake. In transplant experiments a common source (a particular site within a particular lake) should be used, and post-transplant periods of more than 1 year may be necessary for the influence of the destination environment to dominate the influence of the source environment.

scholarly journals An 850 year record of climate and fluctuations of the iceberg-calving Nellie Juan Glacier, south central Alaska, U.S.A.

2003 ◽  
Vol 36 ◽  
pp. 51-56 ◽  
Author(s):  
David J. Barclay ◽  
Gregory C. Wiles ◽  
Parker E. Calkin
Keyword(s):  
Tree Ring ◽  
Late Holocene ◽  
Ring Width ◽  
Tree Ring Width ◽  
Terminal Moraine ◽  
Glacier System ◽  
South Central ◽  
Iceberg Calving ◽  
Paleoclimate Records ◽  
The 19Th Century

AbstractTree-ring cross-dates of 46 glacially killed trees show that the tidewater Nellie Juan Glacier, Alaska, advanced seaward during the 16th and 17th centuries AD. Ice-scarred trees at the late-Holocene end moraine indicate that the terminus was at its recent maximum from 1842 to 1893. Historical observations and photographs show that subsequent slow retreat changed to rapid iceberg-calving retreat after 1935, and that the tidewater terminus had withdrawn about 3.3 km from the late-Holocene maximum by 1992. Comparison with paleoclimate records from nearby land-terminating glaciers and an 850 year tree-ring-width chronology indicates that the timing of the 19th-century maximum stand of Nellie Juan Glacier was controlled by changes in summer temperature and radiation. However, rapid iceberg-calving retreat did not begin until 40 years of slow retreat had brought the tidewater terminus back from the terminal moraine shoal. Therefore, both the dimensions of the terminal moraine shoal and the magnitude and duration of climate change were important in initiating rapid retreat of this tidewater glacier system.

scholarly journals Combining occurrence and abundance distribution models for the conservation of the Great Bustard

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e4160 ◽  
Author(s):  
Chunrong Mi ◽  
Falk Huettmann ◽  
Rui Sun ◽  
Yumin Guo
Keyword(s):  
Species Abundance ◽  
Distribution Patterns ◽  
Bohai Bay ◽  
Residential Areas ◽  
Abundance Distribution ◽  
Great Bustard ◽  
Distribution Models ◽  
South Central ◽  
A Priority ◽  
Protection Index

Species distribution models (SDMs) have become important and essential tools in conservation and management. However, SDMs built with count data, referred to as species abundance models (SAMs), are still less commonly used to date, but increasingly receiving attention. Species occurrence and abundance do not frequently display similar patterns, and often they are not even well correlated. Therefore, only using information based on SDMs or SAMs leads to an insufficient or misleading conservation efforts. How to combine information from SDMs and SAMs and how to apply the combined information to achieve unified conservation remains a challenge. In this study, we introduce and propose a priority protection index (PI). The PI combines the prediction results of the occurrence and abundance models. As a case study, we used the best-available presence and count records for an endangered farmland species, the Great Bustard (Otis tarda dybowskii), in Bohai Bay, China. We then applied the Random Forest algorithm (Salford Systems Ltd. Implementation) with eleven predictor variables to forecast the spatial occurrence as well as the abundance distribution. The results show that the occurrence model had a decent performance (ROC: 0.77) and the abundance model had a RMSE of 26.54. It is noteworthy that environmental variables influenced bustard occurrence and abundance differently. The area of farmland, and the distance to residential areas were the top important variables influencing bustard occurrence. While the distance to national roads and to expressways were the most important influencing abundance. In addition, the occurrence and abundance models displayed different spatial distribution patterns. The regions with a high index of occurrence were concentrated in the south-central part of the study area; and the abundance distribution showed high populations occurrence in the central and northwestern parts of the study area. However, combining occurrence and abundance indices to produce a priority protection index (PI) to be used for conservation could guide the protection of the areas with high occurrence and high abundance (e.g., in Strategic Conservation Planning). Due to the widespread use of SDMs and the easy subsequent employment of SAMs, these findings have a wide relevance and applicability than just those only based on SDMs or SAMs. We promote and strongly encourage researchers to further test, apply and update the priority protection index (PI) elsewhere to explore the generality of these findings and methods that are now readily available.

scholarly journals Diatom Stratigraphy of FA-1 Core, Qarun Lake, Records of Holocene Environmental and Climatic Change in Faiyum Oasis, Egypt

2017 ◽  
Vol 34 (1) ◽  
pp. 61-69 ◽  
Author(s):  
Abdelfattah A. Zalat ◽  
Leszek Marks ◽  
Fabian Welc ◽  
Alaa Salem ◽  
Jerzy Nitychoruk ◽  
...  
Keyword(s):  
Lake Level ◽  
Late Holocene ◽  
Distribution Patterns ◽  
Climatic Conditions ◽  
Anthropogenic Activity ◽  
Diatom Assemblages ◽  
The Holocene ◽  
Arid Conditions ◽  
Diatom Stratigraphy ◽  
Early And Middle Holocene

Abstract This study evaluates changes in the environmental and climatic conditions in the Faiyum Oasis during the Holocene based on diatom analyses of the sediment FA-1 core from the southern seashore of the Qarun Lake. The studied FA-1 core was 26 m long and covered the time span ca. 9.000 cal. yrs BP. Diatom taxa were abundant and moderately to well-preserved throughout the core sediments. Planktonic taxa were most abundant than the benthic and epiphytic forms, which were very rare and sparsely distributed. The most dominant planktonic genera were Aulacoseira and Stephanodiscus followed by frequently distribution of Cyclostephanos and Cyclotella species. The stratigraphic distribution patterns of the recorded diatoms through the Holocene sediments explained five ecological diatom groups. These groups represent distinctive environmental conditions, which were mainly related to climatic changes through the early and middle Holocene, in addition to anthropogenic activity during the late Holocene. Comparison of diatom assemblages in the studied sediment core suggests that considerable changes occurred in water level as well as salinity. There were several high stands of the freshwater lake level during humid, warmer-wet climatic phases marked by dominance of planktonic, oligohalobous and alkaliphilous diatoms alternated with lowering of the lake level and slight increases in salinity and alkalinity during warm arid conditions evident by prevalence of brackish water diatoms.

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