Cambrian stratigraphy of the St. Valentines Peak area, north-western Tasmania

Abstract

An important Late Middle Cambrian fossil locality occurs 2 km west of St. Valentines Peak in north-western Tasmania. The Cambrian rocks to the north and west of St. Valentines Peak are exposed in the core of the north-south trending St. Valentines Peak Anticline. In the best exposed section (3 km north of the main fossil locality), the oldest Cambrian unit is a massive, cherty, pyritic meta-sandstone and meta-siltstone at least 100 m thick. This is overlain by 100 m of rhyolitic welded tuff, 75 to 100 m of meta-sandstones and meta-siltstones, 100 m of a possible contact metasomatic rock and 230 to 375 m of a pale grey chert which in turn is overlain by about 17 m of fine breccia and poorly fossiliferous siltstone. This sequence is overlain with probable disconformity by the basal chert conglomerate of the essentially Ordovician Junee Group. It is suggested that the sediments of the main fossiliferous locality occur stratigraphically below the section noted above. The Cambrian and Ordovician rocks are intruded by Devonian granite and partly overlain by Tertiary basalt.