13 research outputs found
Reply to “Comment on ‘U‐Pb and Hf Isotope Analysis of Detrital Zircons From Mesozoic Strata of the Gravina Belt, Southeast Alaska’ by Yokelson Et Al. (2015)”
No full textU-Pb and Hf isotopic analyses of detrital zircons from the Taku terrane, southeast Alaska
No full textThe Taku terrane consists of metamorphosed Carboniferous through Triassic marine clastic strata, volcanic rocks, and limestone which occur along the western margin of the Coast Mountains in southeastern (SE) Alaska. These rocks are juxtaposed along mid-Cretaceous thrust faults over Jura-Cretaceous basinal strata of the Gravina belt to the west and beneath Proterozoic through Carboniferous metamorphic rocks of the Yukon-Tanana terrane to the east. This paper presents U-Pb ages and Hf isotope analyses of detrital zircons from the Taku terrane, and compares these values with information from the adjacent Wrangellia, Alexander, and northern and southern portions of the Yukon-Tanana terrane (YTTn and YTTs). These comparisons suggest that: (1) Carboniferous strata of the Taku terrane were shed mainly from mid-Paleozoic igneous rocks of YTTs; (2) Permian strata of the Taku terrane were shed from mid-Paleozoic igneous rocks and intraformational Lower Permian volcanic rocks of YTTs as well as Upper Permian volcanic rocks exposed in YTTn; and (3) Triassic sandstones were shed from mid-Paleozoic igneous rocks of YTTs, whereas conglomerates were shed mainly from mid-Paleozoic arc rocks in YTTn. Hf isotope analyses of Paleozoic zircons record increasing continental input during Silurian-Devonian and Permian phases of magmatism. Similarities in isotopic characteristics, combined with stratigraphic and geochemical information presented by previous workers, suggest that strata of the Taku terrane accumulated on (and partly as lateral equivalents of) rocks of YTTs, and that the combined assemblages formed outboard or along strike of YTTn.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
Analyzing the Impact of Evolving Combustion Conditions on the Composition of Wildfire Emissions Using Satellite Data
No full textWildfires have become larger and more frequent because of climate change, increasing their impact on air pollution. Air quality forecasts and climate models do not currently account for changes in the composition of wildfire emissions during the commonly observed progression from more flaming to smoldering combustion. Laboratory measurements have consistently shown decreased nitrogen dioxide (NO2) relative to carbon monoxide (CO) over time, as they transitioned from more flaming to smoldering combustion, while formaldehyde (HCHO) relative to CO remained constant. Here, we show how daily ratios between column densities of NO2 versus those of CO and HCHO versus CO from the Tropospheric Monitoring Instrument (TROPOMI) changed for large wildfires in the Western United States. TROPOMI-derived emission ratios were lower than those from the laboratory. We discuss reasons for the discrepancies, including how representative laboratory burns are of wildfires, the effect of aerosols on trace gas retrievals, and atmospheric chemistry in smoke plumes.Atmospheric Remote Sensin
Geomorphology, denudation rates, and stream channel profiles reveal patterns of mountain building adjacent to the San Andreas fault in northern California, USA
No full textSupplemental material: Detrital zircon U-Pb geochronology and Hf isotope geochemistry of the Yukon-Tanana terrane, Coast Mountains, southeast Alaska
No full textGeosphere, October 2016, v. 12, p. 1556-1574, doi:10.1130/GES01303.1, Supplemental Table 4 - Tracy Arm probability plots (.xls)
Supplemental material: Detrital zircon U-Pb geochronology and Hf isotope geochemistry of the Yukon-Tanana terrane, Coast Mountains, southeast Alaska
No full textGeosphere, October 2016, v. 12, p. 1556-1574, doi:10.1130/GES01303.1, Supplemental Table 2 - Yukon-Tanana terrane U‑Pb isotopic data (.xls)
Supplemental material: Detrital zircon U-Pb geochronology and Hf isotope geochemistry of the Yukon-Tanana terrane, Coast Mountains, southeast Alaska
No full textGeosphere, October 2016, v. 12, p. 1556-1574, doi:10.1130/GES01303.1, Supplemental Table 3 - Yukon-Tanana terrane Hf isotopic data (.xls)
Supplemental material: Detrital zircon U-Pb geochronology and Hf isotope geochemistry of the Yukon-Tanana terrane, Coast Mountains, southeast Alaska
No full textGeosphere, October 2016, v. 12, p. 1556-1574, doi:10.1130/GES01303.1, Supplemental Table 1 - Yukon-Tanana terrane samples and zircon images (.xls)
U-PB GEOCHRONOLOGY AND ZIRCON HF AND O ISOTOPE ANALYSIS OF PLUTONS OF THE SOUTHERN COAST MOUNTAINS BATHOLITH, BRITISH COLUMBIA: INSIGHT INTO EPISODIC MAGMATISM IN CONTINENTAL ARCS
No full textSupplemental material: Detrital zircon U-Pb geochronology and Hf isotope geochemistry of the Yukon-Tanana terrane, Coast Mountains, southeast Alaska
No full textGeosphere, October 2016, v. 12, p. 1556-1574, doi:10.1130/GES01303.1, Supplemental Table 5 - Endicott Arm probability plots (.xls)
