PALEOMAGNETISM AND THE AGE OF THE TUMBLAGOODA SANDSTONE, WESTERN-AUSTRALIA

Whilst acknowledging the geological evidence for a Silurian age of the Tumblagooda Sandstone of Western Australia, this article draws attention to palaeomagnetic data which suggest a significantly older age. The pole position from the Tumblagooda Sandstone provides a strong constraint on the location of the Australian Paleozoic apparent polar wander path (APWP), and by inference on that of the Gondwana APWP. Although the use of this pole as a key pole cannot be justified because the age of the Tumblagooda Sandstone is not reliably known, comparison of this pole with a Siluro-Devonian pole from eastern Australia, and Ordovician to Silurian poles from Africa (in an appropriate pre-breakup reference frame), suggests an age of Ordovician. Palaeontological evidence from large eurypterid tracks suggests a Silurian to Devonian age. While stratigraphic evidence is meagre, isotopic data have been used to support a post-Early Silurian age. However the isotopic data are shown to be compatible with a significantly older age.