HR: 1340h
AN: PP23B-1433    [Abstracts]
TI: OSL Dating of Diatoms: A Potential Application of an Established Chronometric Method
AU: Rieser, U
EM: Uwe.Rieser@vuw.ac.nz
AF: Luminescence Dating Laboratory, School of Earth Sciences, Victoria University Wellington, PO Box 600, Wellington, unknown New Zealand
AU: * Edsall, D W
EM: edsall@usna.edu
AF: Physics Department, U.S. Naval Academy, 353 Ricketts Hall, Annapolis, MD 21402 United States
AB: G.A. Wagner (1998) lists 65 different geological, archaeological and historical materials that can be dated by a broad spectrum of chronometric methods. OSL ages of diatoms would contribute to studies of paleoclimatological and chronological significance which until now have been obtained using TL, 226Pa and 32Si methods. OSL dating of diatom tests has been attempted at the Luminescence Dating Laboratory, School of Earth Sciences, Victoria University Wellington. Two samples differing in age, origin (fresh water and marine) and genus/species were selected for dating. Until now, OSL dating of continental and marine sediments has focused on materials of inorganic origin and siliceous composition. This study's diatom tests have been buried concomitantly with such materials and hence exposed to the same doses of radiation so a direct comparison of ages can be made. Although diatom skeletal composition is opaline and structure is amorphous not crystalline, the diatom tests may contain long-term stable traps in microcrystalline phases. Trials of methods of diatom isolation and preparation, determination of light sensitivity, dose dependency and long-term stability of diatoms are described and age results presented for diatoms from two cores. The first, late-Pleistocene freshwater diatom ooze (dominant Cyclotella stelligera), is from the Auckland New Zealand Pukaki Maar Crater (core Pukaki 1-01). It has excellent independent age control from associated Kawakawa and Rotoehu tephras ($>$26 and $<55$ ka). The second is a RV Maurice Ewing northern North Atlantic Ocean core containing marine isotope substage 5e (130-115 ka BP) monospecific laminated diatom ooze (pinnate diatom- Thalassiothrix longissima). Our results reflect the need to attend to preparation, dose dependence, stability, measurement parameters and signal detection. The potential and problems of OSL-based chronometric studies utilizing diatoms will be reported. Additional studies of an extended suite of diatom bearing samples are planned.
DE: 9604 Cenozoic
DE: 4267 Paleoceanography
DE: 3030 Micropaleontology
DE: 1035 Geochronology
DE: 1094 Instruments and techniques
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting