Tectonic control on development of a Frasnian‐Famennian (Late Devonian) palaeokarst surface, Canning Basin reef complexes, northwestern Australia

Abstract

The Frasnian-Famennian boundary in the Canning Basin has long been associated with a shelf-wide, short-lived fall in relative sea-level. A near-planar palaeokarst surface, separating Frasnian proximal forereef and Famennian backreef facies, locally marks the boundary in the northwestern Lennard Shelf (Chedda Cliffs area, northern Napier Range). Surface and subsurface relationships between the Frasnian and Famennian strata suggest that a major episode of normal faulting and associated tilting in the latest Frasnian uplifted the platform margin to subaerially expose and erode all of the margin and uppermost forereef facies. Tectonic control on the development of this Frasnian-Famennian palaeokarst surface questions the interpretation of a simple, shelf-wide eustatically driven relative sea-level fall. Instead, a tectonic event affecting the northwestern Lennard Shelf, coupled with widespread recognition of a reduction in carbonate production at or very near the Frasnian-Famennian boundary elsewhere on the shelf, supports earlier interpretations of a major phase of basin-margin uplift related to extension along basin-bounding faults.