New Constraints on Ages of Glasses Proposed as Reference Materials for Fission‐Track Dating

Abstract

New analyses have been performed in order to enhance the data‐set on the independent ages of four glasses that have been proposed as reference materials for fission‐track dating. The results are as follows. Moldavite ‐ repeated 40Ar/39Ar age determinations on samples from deposits from Bohemia and Moravia yielded an average of 14.34 ± 0.08 Ma. This datum agrees with other recent determinations and is significantly younger than the 40Ar/39Ar age of 15.21 ± 0.15 Ma determined in the early 1980s. Macusanite (Peru) ‐four K‐Ar ages ranging from 5.44 ± 0.06 to 5.72 ± 0.12 Ma have been published previously. New 40Ar/39Ar ages gave an average of 5.12 ± 0.04 Ma. Plateau fission‐track ages determined using the IRMM‐540 certified glass and U and Th thin films for neutron fluence measurements agree better with these new 40Ar/39Ar ages than the previously published ages. Roccastrada glass (Italy) ‐ a new 40Ar/39Ar age, 2.45 ± 0.04 Ma, is consistent with previous determinations. The Quiron obsidian (Argentina) is a recently discovered glass that has been proposed as an additional reference material for its high spontaneous track density (around 100 000 cm‐2). Defects that might produce “spurious” tracks are virtually absent. An independent 40Ar/39Ar age of 8.77 ± 0.09 Ma was determined and is recommended for this glass. We believe that these materials, which will be distributed upon request to fission‐track groups, will be very useful for testing system calibrations and experimental procedures.

Fission track age of Transantarctic Mountain microtektites

“…Microtektites were analysed using standard fission track dating techniques established at the Istituto di Geoscienze e Georisorse in Pisa (e.g., Laurenzi et al, 2007). Of the 120 microtektites selected for the present study 90 were used for spontaneous track counting.…”

40Ar–39Ar laser dating of tektites from the Cheb Basin (Czech Republic): Evidence for coevality with moldavites and influence of the dating standard on the age of the Ries impact

“…(g) Data reported by Aziz et al (2008); bars as in (c). (h and i) Fission track data for moldavites (after correction for track annealing) based on different reference glasses, from Bouška et al (2000) and Laurenzi et al (2007); error-weighted means were calculated using the Isoplot/Ex program, v. 3.00 (Ludwig, 2003). of the ASCR, Prague).…”

“…2). Bias due to calibration problems seems to also affect recent fission track data (Bouška et al, 2000;Laurenzi et al, 2007). When corrected for track annealing, the fission track data based on two different reference glasses ( Fig.…”

Volcanic Glass (Fission Track)

“…The most commonly used FT dating method is the zeta calibration method based on analysis of age standards (Hurford and Green 1983), which, in the case of glass-FT dating, is the Moldavite tektite with an age of 14.34 AE 0.08 Ma (Laurenzi et al 2003(Laurenzi et al , 2007). An age can be determined by measuring three areal track densities, spontaneous track density (r s ), induced track density (r i ), and induced track density of the dosimeter glass (r d ) or its muscovite external detector.…”

“…Acceptable ages can now be obtained on glass shards as small as $80 mm. It follows, therefore, that these grain-specific FT methods are ideally suited to the dating of distal tephra beds, which are typically thin, discontinuous, fine-grained, and (Laurenzi et al 2003(Laurenzi et al , 2007. Ages in Ma unless otherwise noted; 1s given Encyclopedia of Scientific Dating Methods DOI 10.1007/978-94-007-6326-5_60-1 # Springer Science+Business Media Dordrecht 2014 contaminated.…”