Stratigraphy and palaeovolcanology of the Cambrian Tyndall group, Mt Read Volcanics, western Tasmania

Abstract

The Tyndall Group is a Cambrian, dominantly submarine, volcano‐sedimentary succession that occurs in the upper part of the Mt Read Volcanics, western Tasmania. The internal stratigraphy of the Tyndall Group is relatively complex, comprising a wide variety of lithofacies including crystal‐ and lithic‐rich volcaniclastic breccia, conglomerate and sandstone, welded ignimbrite, rhyolite, laminated mudstone and carbonate. Problems with the previously defined stratigraphic nomenclature have prompted development of a new stratigraphic scheme, based on detailed facies analysis of major Tyndall Group exposures in the central Mt Read Volcanics. The Tyndall Group is divided into two formations, the Comstock Formation and the overlying Zig Zag Hill Formation. The Comstock Formation is subdivided into the Lynchford Member and the overlying Mt Julia Member. This stratigraphic scheme is based on regional lithological variations, which largely reflect different provenance characteristics. In both formations, volcaniclast...