Devonian goniatite biostratigraphy and timing of facies movements in the Frasnian of the Canning Basin, Western Australia

Abstract

Abstract As part of an international study of Devonian facies movements against cratonic areas an investigation has been undertaken of the timing of facies movements associated with the Frasnian and Famennian reef complexes of the Canning Basin, Western Australia. This led to the discovery of rich goniatite faunas which enable significant improvements to be made to the high resolution ammonoid time scale. A new goniatite classification for the Frasnian is proposed for international use based on the entry of particular genera; this gives 12 divisions. A much more detailed regional zonation is proposed for the Canning Basin. As part of this, a description is given of the following new genera of the Gephuroceratidae: Gogoceras, Playfordites, Serramanticoceras and Mixomanticoceras . The genus Probeloceras is used in a restricted sense and recognised as the first member of the Beloceratidae; Acanthoclymenia is used for forms previously assigned loosely to Probeloceras . The new zonation provides a framework for analysis of facies movements. Occasions of anoxic or hypoxic events are indicated by rich, hematized goniatite faunas. Reef backstepping associated with deepening is dateable by goniatites in associated marginal slope deposits. Several of the international eustatic sea-level changes are recognised, noticeably those correlative with the Genundewa, Middlesex and Rhinestreet deepenings of New York. No evidence has been found for the internationally widespread ‘Kellwasserkalk’ facies in the late Frasnian, but a succession of terminal Frasnian sea-level changes is recognized. The ‘Irtidium Anomaly’ level lies well above the Frasnian/Famennian boundary and hence provides no confirmation of a bolide to explain Frasnian/Famennian boundary extinctions. In the Famennian, evidence for the European Condroz regression and Annulata deepening is presented.