Late Quaternary volcanic activity in Marie Byrd Land: Potential 40Ar/39Ar-dated time horizons in West Antarctic ice and marine cores

Abstract

Research Article| October 01, 1999 Late Quaternary volcanic activity in Marie Byrd Land: Potential 40Ar/39Ar-dated time horizons in West Antarctic ice and marine cores T. I. Wilch; T. I. Wilch 1Department of Geological Sciences, Albion College, Albion, Michigan 49224 Search for other works by this author on: GSW Google Scholar W. C. McIntosh; W. C. McIntosh 2Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology3New Mexico Bureau of Mines and Mineral Resources, Socorro, New Mexico 87801 Search for other works by this author on: GSW Google Scholar N. W. Dunbar N. W. Dunbar 3New Mexico Bureau of Mines and Mineral Resources, Socorro, New Mexico 87801 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1999) 111 (10): 1563–1580. https://doi.org/10.1130/0016-7606(1999)111<1563:LQVAIM>2.3.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation T. I. Wilch, W. C. McIntosh, N. W. Dunbar; Late Quaternary volcanic activity in Marie Byrd Land: Potential 40Ar/39Ar-dated time horizons in West Antarctic ice and marine cores. GSA Bulletin 1999;; 111 (10): 1563–1580. doi: https://doi.org/10.1130/0016-7606(1999)111<1563:LQVAIM>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Late Quaternary volcanic activity at three major alkaline composite volcanoes in Marie Byrd Land, West Antarctica, is dominated by explosive eruptions, many capable of depositing ash layers as regional time-stratigraphic horizons in the West Antarctic Ice Sheet and in Southern Ocean marine sediments. A total of 20 eruptions at Mount Berlin, Mount Takahe, and Mount Siple are recorded in lava and welded and nonwelded pyroclastic fall deposits, mostly peralkaline trachyte in composition. The eruptions, dated by the 40Ar/39Ar laser-fusion and furnace step-heating methods, range in age from 571 to 8.2 ka.Tephra from these 40Ar/39Ar-dated Marie Byrd Land eruptions are identified by geochemical fingerprinting in the 1968 Byrd Station ice core. The 74 ka ice-core record contained abundant coarse ash layers, with model ice-flow ages ranging from 7.5 to 40 ka, all of which were previously geochemically correlated to the Mount Takahe volcano. We identify a one-to-one geochemical and age correlation of the youngest (ca. 7.5 ka) tephra layer in the Byrd ice core to an 8.2 ± 5.4 ka (2sigma uncertainty) pyroclastic deposit at Mount Takahe. We infer that the 20–30 ka tephra layers in the Byrd ice core actually were erupted from Mount Berlin, on the basis of age and geochemical similarities. If products of these youngest, as well as the older 40Ar/39Ar-dated eruptions are identified by geochemical fingerprinting in future ice and marine cores, they will provide the cores with independently dated time horizons.More than 12 40Ar/39Ar-dated tephra layers, exposed in bare ice on the summit ice cap of Mount Moulton, 30 km from their inferred source at Mount Berlin, range in age from 492 to 15 ka. These englacial tephra layers provide a minimum age of 492 ka for the oldest isotopically dated ice in West Antarctica. This well-dated section of locally derived glacial ice contains a potential “horizontal ice core” record of paleoclimate that extends back through several glacial-interglacial cycles. The coarse grain size and density of the englacial tephra (mean diameters 17–18 mm, densities 540–780 kg/m3), combined with their distance from source, indicate derivation from highly explosive Plinian eruptions of Mount Berlin. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.