Late Devonian carbon isotope stratigraphy and sea level fluctuations, Canning Basin, Western Australia

Abstract

The Upper Devonian reef complexes of the Canning Basin contain some of the world’s best exposed, continuous stratigraphic sections through the Frasnian–Famennian boundary. The facies distribution and composition of these reef complexes record interactions among sea level changes, sediment supply, ocean chemistry, and paleoecology. Changes in relative sea level produced spatial shifts in reef platform development and regional changes in sediment supply that can be correlated across facies boundaries using a combination of sequence stratigraphy, biostratigraphy, and carbon isotope stratigraphy. During the lowstand interval below the Frasnian–Famennian boundary, the reef margin advanced down the reef slope in shallow-water environments, and siliciclastics locally dominated in the marginal slope environment. Compilation of a broad late Frasnian to early Famennian sequence stratigraphic framework for the Canning Basin demonstrates that transgressive intervals correlate to positive carbon isotopic excursions within the basin. These isotopic shifts also can be correlated to time-equivalent positive carbon isotopic excursions reported from transgressive intervals in Europe. Thus, the late Frasnian transgressions in the Canning Basin were primarily eustatic rather than tectonic in origin, and positive carbon isotopic signatures of the Kellwasser horizons are globally correlative.