ABSTRACT: Sequence Stratigraphic Analysis of the Permian Succession in the Western Bowen Basin, Queensland; Implications for Hydrocarbon Exploration
ZIOLKOWSKI, V., and C. R. FIELDING,* Department of Geology and Mineralogy, University of Queensland, Queensland, M. WILKINSON, AGL Petroleum Pty. Ltd., Brisbane, Queensland, and J. J. DRAPER, Department of Resource Industries, Brisbane, Queensland
Recent literature on sequence stratigraphic analysis of sedimentary successions has concentrated on the study of passive continental margin, resulting in the development of somewhat idealized models for sequences architecture in sedimentary basins (Van Wagoner et al., 1990). This paper aims to establish a sequence stratigraphy based upon extensive outcrop and subsurface data for a basin formed in a retroarc setting, the Bowen basin of Queensland. Analysis of Permian sequences in the western part of the basin (cratonic margin) has revealed a complex interplay between tectonic and eustatic effects, reflecting the evolution of the basin from a back-arc extensional trough to a true, retroarc foreland basin through time. The sequence architecture in the Denison Trough shows considerable de arture from conventional models of sequence development based fundamentally on passive margins.
According to conventional models, in passive margin development siliciclastic sediment dispersal is unimodal, impinging on a continental shelf and slope of infinite capacity which are subsiding in a predictable fashion about a continental margin hinge point. High frequency eustatic cycles can readily be separated from this passive tectonism, and resultant systems tracts carry a recognizable signature. Such systems tracts can therefore be assigned to various phases of a simple, sinusoidal eustatic cycle (Van Wagoner et al., 1990).
In the case of retroarc foreland systems, the cratonic margin hingepoint is unpredictably mobile and cannot readily be defined due to the presence of active faulted margins, movement of depocenters through time and consequent uplift and erosion. Foreland basins also exhibit bimodality of sediment provenance, as early stage sediments shed from the craton are later overwhelmed by material derived from the evolving orogen. Depocenters become progressively restricted or isolated from the open marine systems of the forearc. According to sequence stratigraphic models, platform sediments can only accumulate during highstands, while lowstands are recorded by erosion. In foreland systems, however, it can be demonstrated that major regressive pulses occur during active tectonism. These regressi ns cannot be considered to be in phase with eustatic cyclicity, and must be treated as composites of the two independent controls.
AAPG Search and Discovery Article #91015©1992 AAPG International Conference, Sydney, N.S.W., Australia, August 2-5, 1992 (2009)