Williams, A.J., Stuart, F.M., Day, S.J. and Phillips, W.M. (2005) Using pyroxene microphenocrysts to determine cosmogenic 3He concentrations in old volcanic rocks: an example of landscape development in central Gran Canaria. Quaternary Science Reviews, 24(1-2), pp. 211-222. (doi: 10.1016/j.quascirev.2004.07.004)
Full text not currently available from Enlighten.
Publisher's URL: http://dx.doi.org/10.1016/j.quascirev.2004.07.004
Abstract
Determinations of cosmogenic <sup>3</sup>He exposure ages and erosion rates in volcanic rocks older than a few hundred thousand years are complicated by the presence of radiogenic He in addition to the magmatic and cosmogenic He, in phenocryst minerals. However, by analysing microphenocrysts (that crystallised on or immediately prior to eruption) that have not trapped magmatic He, the threecomponent problem can be eliminated and accurate determinations of cosmogenic <sup>3</sup>He made. In this study, we perform three experiments using pyroxene microphenocrysts in basaltic clasts in the Pliocene Ayacata Formation breccias, Gran Canaria, that demonstrate they are free of magmatic He. Exposure ages and erosion rates calculated from the cosmogenic <sup>3</sup>He concentrations are combined with a geomorphological study, to produce a tentative interpretation of landscape evolution in the mountainous interior of Gran Canaria. Long-term steady- state erosion rates of 14-24 mm ka(-1) are recorded from bedrock erosional surfaces on a high plateau. Headwall retreat rates for a major drainage system of 1.6 m ka(-1) have been constrained from the ca 225 ka exposure age of a boulder emplaced on slopes beneath the headwall. Strath terraces and boulders in a small canyon system yield much younger exposure ages of 47-43 ka.
Item Type: | Articles |
---|---|
Status: | Published |
Refereed: | Yes |
Glasgow Author(s) Enlighten ID: | Stuart, Professor Fin |
Authors: | Williams, A.J., Stuart, F.M., Day, S.J., and Phillips, W.M. |
Subjects: | Q Science > QE Geology |
College/School: | College of Science and Engineering > Scottish Universities Environmental Research Centre |
Journal Name: | Quaternary Science Reviews |
ISSN: | 0277-3791 |
University Staff: Request a correction | Enlighten Editors: Update this record