The Laidlaw Volcanics: a Late Silurian point on the geological time scale
Abstract
Mapping, mineralogical and chemical studies of an area west and northwest of Canberra, southeastern Australia, have shownthat the Laidlaw Volcanics are unique in the region, and that their age is tightly controlled stratigraphically as they lie both above and below Early Ludlow (Late Silurian) fossiliferous sediments. K-Ar mineral analyses, previously published Rb-Sr mineral analyses, and new Rb-Sr wholerock and mineral analyses together give the Laidlaw Volcanics an age of 420.7 ± 2.2 m.y. This result for the Early Ludlow is identical numerically with a recently published age of 421±3 m.y. for the Ashgillian (Late Ordovician) Stockdale Rhyolite, and suggests either that the time interval between the Ashgill and Ludlow does not exceed a few million yearsor that the age estimate for the Stockdale Rhyolite is too young.
- Publication:
-
Earth and Planetary Science Letters
- Pub Date:
- June 1982
- DOI:
- 10.1016/0012-821X(82)90119-4
- Bibcode:
- 1982E&PSL..59...90W