K. L. Bann and C. R. Fielding

University of Queensland, Australia

ABSTRACT: High-Resolution Sequence Stratigraphy of Reservoirs in the Bowen Basin, Queensland, Australia, Facilitated by Ichnological Analysis

Early and Early Late Permian sequences in the western Bowen Basin of Queensland, Australia, are productive conventional gas reservoirs. Attempts to interpret the reservoir bodies in terms of depositional environments have largely relied on sedimentary facies analysis and palynology. Re- evaluation of sequences from a detailed and comprehensive ichnological perspective has significantly increased the precision and resolution of the palaeoenvironmental interpretation and facilitated a high frequency model of relative sea-level change.

Coastal deposits in the Freitag Formation at Fairbairn Dam have been re-evaluated using ichnological analysis. Previously overlooked marine shoreface successions have been identified and a high frequency relative sea-level curve established. The Skolithos, Cruziana and Arenicolites ichnofacies were identified. The subdivision of the Skolithos and Cruziana ichnofacies into proximal, distal and restricted facies has facilitated the differentiation of heterolithic, interbedded sand/silt units into interdistributary bay deposits and interbedded shoreface deposits.

A shoreface succession in the German Creek Formation at Bundoora spillway has been re- interpreted with the use of ichnology. The recognition of proximal Cruziana, distal Skolithos and Skolithos ichnofacies has facilitated the recognition of different shoreface environments. A previously overlooked Glossifungites ichnofacies demarks an erosive event and a sedimentary hiatus. The increase in resolution of palaeoenvironmental interpretation has facilitated an enhanced depositional history and a high-resolution sequence stratigraphic framework.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado