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Boreal lake sediments are important sites of organic carbon (OC) storage, which have accumulated substantial amounts of OC over the Holocene epoch; the temporal evolution and the strength of this Holocene carbon (C) sink is, however, not well constrained. In this study we investigated the temporal record of carbon mass accumulation rates (CMARs) and assessed qualitative changes of terrestrially derived OC in the sediment profiles of seven Swedish boreal lakes, in order to evaluate the variability of boreal lake sediments as a C sink over time. CMARs were resolved on a short-term (centennial) and long-term (i.e., over millennia of the Holocene) timescale, using radioactive lead (210Pb) and carbon (14C) isotope dating....
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The 2002 Mw 7.9 Denali Fault earthquake, Alaska, provides an unparalleled opportunity to investigate in quantitative detail the regional hillslope mass-wasting response to strong seismic shaking in glacierized terrain. We present the first detailed inventory of ∼1580 coseismic slope failures, out of which some 20% occurred above large valley glaciers, based on mapping from multi-temporal remote sensing data. We find that the Denali earthquake produced at least one order of magnitude fewer landslides in a much narrower corridor along the fault ruptures than empirical predictions for an M ∼8 earthquake would suggest, despite the availability of sufficiently steep and dissected mountainous topography prone to frequent...
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Investigated herein are water and sediment geochemistry, and metal attenuation processes associated with natural acid rock drainage originating from black shale formations in the Macmillan Pass area, Clear Lake prospect and Engineer Creek by the Dempster Highway in the Yukon Territory, Canada. The most metalliferous water having pH 3.0, 150 mg/L Zn, 39 mg/L Ni, 2.8 mg/L Cu and 9.1 mg/L As was found in a tributary stream of Engineer Creek with no known mineral deposits occurring in the vicinity. For all three study areas, the water and sediment geochemistry is significantly affected by the local lithology and prevailing metal attenuation processes. Despite their anomalous acidity and metal contents, the natural acid...
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At sites where petrochemical releases have occurred comparatively recently (i.e., over the last 20 years), explicit age-dating is a viable approach. However, differentiating among multiparty contamination at sites with several decades of history may mandate a different allocation strategy, especially when there is an uncoordinated body of environmental data. At a location where a refinery operated for 11 months during World War II, and which has been used as a fuel distribution terminal over the ensuing 60 years, regulatory interest was triggered in 1997 when a sheen was detected discharging into the adjacent Yukon River. Our investigation combined disparate forensic tools with data visualization software to establish...
Climate change has increased the area affected by forest fires each year in boreal North America. Increases in burned area and fire frequency are expected to stimulate boreal carbon losses. However, the impact of wildfires on carbon emissions is also affected by the severity of burning. How climate change influences the severity of biomass burning has proved difficult to assess. Here, we examined the depth of ground-layer combustion in 178 sites dominated by black spruce in Alaska, using data collected from 31 fire events between 1983 and 2005. We show that the depth of burning increased as the fire season progressed when the annual area burned was small. However, deep burning occurred throughout the fire season...
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The article discusses the analysis of geochemical samples from the Geological Survey and Bureau of Mines (USBM) by the Alaska Division of Geological & Geophysical Surveys (DGGS). Topics included are the evaluation of Strategic and Critical Minerals (SCM) content of central Alaska Ray River watershed specimen, the documentation of location coordinates and pulp preparation methodology, and the analysis of rare earth and ore elements by ALS Minerals Laboratories.
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In 2005 the Alaska Division of Geological & Geophysical Surveys initiated a multi-year geologic field study focused on a corridor centered along the Alaska Highway between Delta Junction and the Canada border. The purpose of this project is to provide geologic information relevant to a proposed Alaska-Canada natural gas pipeline and other future development in the corridor. Identification of active faults and characterization of seismic hazards were included in the project. During the 2006 and 2007 field seasons, lineaments and geologic features indicative of possible youthful surface faulting in or near the western half of the corridor between Delta Junction and Dot Lake were identified and evaluated. Four of the...
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A systematic water-quality study of the Fortymile River and many of its major tributaries in eastern Alaska was conducted in June of 1997 and 1998. Surface-water samples were collected for chemical analyses to establish regional baseline geochemistry values and to evaluate the possible environmental effects of suction-dredge placer gold mining and bulldozer-operated placer gold mining (commonly referred to as “cat mining”). In general, the water quality of the Fortymile River is very good, with low total dissolved solids and only two cases in which the concentration of any element exceeded primary or secondary drinking-water quality standards. In both cases, iron exceeded secondary drinking-water limits. At...
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The Late Cretaceous Surprise Lake batholith in the Atlin district of northern British Columbia is a highly differentiated, fluoritic, and peraluminous subalkaline body of adamellite-granite composition. The presence of miarolitic cavities and chilled, fine-grained margins suggests it was emplaced at a high structural level, and its trace element signature indicates it has some within-plate granitoid characteristics. The batholith shows many chemical similarities to the I-type igneous rocks associated with W skarns in British Columbia, although it averages >2,700 ppm F, whereas plutons related to W skarns average <400 ppm F. It also shares similar characteristics to the Seagull batholith in south-central Yukon which,...
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A high-resolution column of 57 loess samples was collected from the Dry Creek archaeological site in the Nenana River Valley in central Alaska. Numerical grain-size partitioning using a mixed Weibull function was performed on grain-size distributions to obtain a reconstructed record of wind intensity over the last ~15,000 yr. Two grain-size components were identified, one with a mode in the coarse silt range (C1) and the other ranging from medium to very coarse sand (C2). C1 dominates most samples and records regional northerly winds carrying sediment from the Nenana River. These winds were strong during cold intervals, namely, the Carlo Creek glacial readvance (14.2–14 ka), a late Holocene Neoglacial period (4.2–2.7...
map background search result map search result map Principal facts for gravity data collected in the Copper River basin area, southcentral Alaska Quaternary glacial, lacustrine, and fluvial interactions in the western Noatak basin, northwest Alaska The Geochemistry of Three Tin-Bearing Skarns and Their Related Plutonic Rocks, Atlin, Northern British Columbia Regional baseline geochemistry and environmental effects of gold placer mining operations on the Fortymile River, eastern Alaska Circumpolar Active Layer Monitoring (CALM) sites in the Mackenzie Valley, northwestern Canada Active and Potentially Active Faults in Or Near the Alaska Highway Corridor, Dot Lake to Tetlin Junction, Alaska Analyses of Historic U.S. Bureau of Mines Samples for Geochemical Trace-Element and Rare-Earth-Element Data from the Ray River Watershed, and Kanuti and Hodzana Rivers Uplands, Central Alaska Flank collapse at Mount Wrangell, Alaska, recorded by volcanic mass-flow deposits in the Copper River lowland Why so few? Landslides triggered by the 2002 Denali earthquake, Alaska Natural acid rock drainage associated with black shale in the Yukon Territory, Canada Use of Geochemical Forensics to Determine Release Eras of Petrochemicals to Groundwater, Whitehorse, Yukon Late-glacial alpine glacier advance and early Holocene tephras, northern British Columbia Variations in late Quaternary wind intensity from grain-size partitioning of loess deposits in the Nenana River Valley, Alaska Evidence of soil nutrient availability as the proximate constraint on growth of treeline trees: Reply An open-path tunable diode laser absorption spectrometer for detection of carbon dioxide at the Bonanza Creek Long-Term Ecological Research Site near Fairbanks, Alaska Variations in late Quaternary wind intensity from grain-size partitioning of loess deposits in the Nenana River Valley, Alaska Use of Geochemical Forensics to Determine Release Eras of Petrochemicals to Groundwater, Whitehorse, Yukon An open-path tunable diode laser absorption spectrometer for detection of carbon dioxide at the Bonanza Creek Long-Term Ecological Research Site near Fairbanks, Alaska The Geochemistry of Three Tin-Bearing Skarns and Their Related Plutonic Rocks, Atlin, Northern British Columbia Late-glacial alpine glacier advance and early Holocene tephras, northern British Columbia Analyses of Historic U.S. Bureau of Mines Samples for Geochemical Trace-Element and Rare-Earth-Element Data from the Ray River Watershed, and Kanuti and Hodzana Rivers Uplands, Central Alaska Flank collapse at Mount Wrangell, Alaska, recorded by volcanic mass-flow deposits in the Copper River lowland Active and Potentially Active Faults in Or Near the Alaska Highway Corridor, Dot Lake to Tetlin Junction, Alaska Evidence of soil nutrient availability as the proximate constraint on growth of treeline trees: Reply Quaternary glacial, lacustrine, and fluvial interactions in the western Noatak basin, northwest Alaska Regional baseline geochemistry and environmental effects of gold placer mining operations on the Fortymile River, eastern Alaska Principal facts for gravity data collected in the Copper River basin area, southcentral Alaska Natural acid rock drainage associated with black shale in the Yukon Territory, Canada Why so few? Landslides triggered by the 2002 Denali earthquake, Alaska Circumpolar Active Layer Monitoring (CALM) sites in the Mackenzie Valley, northwestern Canada