Record of middle Pleistocene climate change from Buck Lake, Cascade Range, southern Oregon—Evidence from sediment magnetism, trace-element geochemistry, and pollen

Abstract

Research Article| October 01, 1996 Record of middle Pleistocene climate change from Buck Lake, Cascade Range, southern Oregon—Evidence from sediment magnetism, trace-element geochemistry, and pollen Joseph G. Rosenbaum; Joseph G. Rosenbaum 1U.S. Geological Survey, Box 25046, M.S. 980, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar Richard L. Reynolds; Richard L. Reynolds 1U.S. Geological Survey, Box 25046, M.S. 980, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar David P. Adam; David P. Adam 2U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar John Drexler; John Drexler 3Department of Geological Sciences, University of Colorado, Boulder, Colorado 80309 Search for other works by this author on: GSW Google Scholar Andrei M. Sarna-Wojcicki; Andrei M. Sarna-Wojcicki 2U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Gene C. Whitney Gene C. Whitney 1U.S. Geological Survey, Box 25046, M.S. 980, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar Author and Article Information Joseph G. Rosenbaum 1U.S. Geological Survey, Box 25046, M.S. 980, Denver, Colorado 80225 Richard L. Reynolds 1U.S. Geological Survey, Box 25046, M.S. 980, Denver, Colorado 80225 David P. Adam 2U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 John Drexler 3Department of Geological Sciences, University of Colorado, Boulder, Colorado 80309 Andrei M. Sarna-Wojcicki 2U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 Gene C. Whitney 1U.S. Geological Survey, Box 25046, M.S. 980, Denver, Colorado 80225 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1996) 108 (10): 1328–1341. https://doi.org/10.1130/0016-7606(1996)108<1328:ROMPCC>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 Joseph G. Rosenbaum, Richard L. Reynolds, David P. Adam, John Drexler, Andrei M. Sarna-Wojcicki, Gene C. Whitney; Record of middle Pleistocene climate change from Buck Lake, Cascade Range, southern Oregon—Evidence from sediment magnetism, trace-element geochemistry, and pollen. GSA Bulletin 1996;; 108 (10): 1328–1341. doi: https://doi.org/10.1130/0016-7606(1996)108<1328:ROMPCC>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 Comparison of systematic variations in sediment magnetic properties to changes in pollen assemblages in middle Pleistocene lake sediments from Buck Lake indicates that the magnetic properties are sensitive to changes in climate. Buck Lake is located in southern Oregon just east of the crest of the Cascade Range. Lacustrine sediments, from 5.2 to 19.4 m in depth in core, contain tephra layers with ages of ≈300–400 ka at 9.5 m and ≈400–470 ka at 19.9 m. In these sediments magnetic properties reflect the absolute amount and relative abundances of detrital Fe-oxide minerals, titanomagnetite and hematite. The lacustrine section is divided into four zones on the basis of magnetic properties. Two zones (19.4–17.4 m and 14.5–10.3 m) of high magnetic susceptibility contain abundant Fe oxides and correspond closely to pollen zones that are indicative of cold, dry environments. Two low-susceptibility zones (17.4–14.5 m and 10.3–5.3 m) contain lesser amounts of Fe oxides and largely coincide with zones of warm-climate pollen. Transitions from cold to warm climate based on pollen are preceded by sharp changes in magnetic properties. This relation suggests that land-surface processes responded to these climate changes more rapidly than did changes in vegetation as indicated by pollen frequencies. Magnetic properties have been affected by three factors: (1) dissolution of Fe oxides, (2) variation in heavy-mineral content, and (3) variation in abundance of fresh volcanic rock fragments. Trace-element geochemistry, employing Fe and the immobile elements Ti and Zr, is utilized to detect postdepositional dissolution of magnetic minerals that has affected the magnitude of magnetic properties with little effect on the pattern of magnetic-property variation. Comparison of Ti and Zr values, proxies for heavy-mineral content, to magnetic properties demonstrates that part of the variation in the amount of magnetite and nearly all of the variation in the amount of hematite are due to changes in heavy-mineral content. Variation in the quantity of fresh volcanic rock fragments is the other source of change in magnetite content. Magnetic-property variations probably arise primarily from changes in peak runoff. At low to moderate flows magnetic properties reflect only the quantities of heavy minerals derived from soil and highly weathered rock in the catchment. At high flows, however, fresh volcanic rock fragments may be produced by breaking of pebbles and cobbles, and such fragments greatly increase the magnetite content of the resulting sediment. Climatically controlled factors that would affect peak runoff levels include the accumulation and subsequent melting of winter snow pack, the seasonality of precipitation, and the degree of vegetation cover of the land surface.Our results do not distinguish among the possible contributions of these disparate factors. 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.