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6. Southwest Bowen Basin Study Area - Wunger
Ridge Flank
6.1. Seismic Interpretation
6.1.1. Previous Work and Structural Framework
A regional interpretation of the Bowen Basin was carried out in the 1990’s by the then Bureau of
Mineral Resources, now Geoscience Australia, in conjunction with what is now the Queensland
Department of Natural Resources, Mines and Energy (QDNRME). The interpretation used regional
seismic lines tied to a regional array of wells as well as deep crustal transects. Significantly more
seismic data existed locally within the Wunger Ridge flank study area than were utilised in the
regional studies, so that fault trends and maps of individual horizons interpreted by the Bureau of
Mineral Resources (data and interpretation available from Geoscience Australia) were considered
too generalised for the purpose of this study. All available seismic data within the Wunger Ridge
flank study area (Figure 2.2c) were thus used so as to produce a more detailed interpretation.
This section presents interpretive results: detailed geophysical reviews are summarised in
(Appendix 10.6.6.).
Previous regional interpretations included those carried out at a sequence stratigraphy level (Brakel
et al., in press); deep crustal transect level (Korsch et al., 1992) and at a regional structural and
exploration level (Korsch et al., 1998; Shaw et al., 1999).
Key tectono-history summaries contained in the above references, and pertinent to the study area,
are summarised below.
• A late Carboniferous to Early Permian extensional or rift phase is recognised in the Bowen
Basin from the presence of large-scale half grabens and associated extrusion of volcanic
rocks (Korsch et al., 1992). Large scale faults imaged on deep crustal transects were not
observed on the shallow seismic data used in this study.
• During the Permian, the rift phase and subsequent thermal subsidence phase switched to a
compressional regime associated with east-to-west thrust belts. These thrusts were imaged
on deep crustal transects and observed in outcrop geology (Korsch et al., 1992). Foreland
loading from the east during the late Permian to mid Triassic produced significant downwarping
of the Taroom Trough (Figure 3.5): the Trough received significant sedimentation
from the east resulting in the deposition of the Rewan Formation. It is interpreted that downwarping
of the Taroom Trough in the east may have caused some degree of flexure in the
west, probably resulting in relatively low accommodation space in the west Bowen Basin.
• The final Bowen Basin phase in the mid–late Triassic was one of uplift and erosion, forming
the unconformable boundary between the Bowen and the overlying Surat Basin.
6.1.2. Time Interpretation
Seismic horizons
Six seismic horizons were interpreted within the study area, and an additional two horizons were
phantomed (copied from an already interpreted horizon and shifted in time (Table 6.1).
For example, the Showgrounds Sandstone was phantomed down from the Snake Creek Mudstone
due to the thin interval that prevented the resolution of both horizons within acceptable accuracy on
printed sections. The Rewan Formation was also phantomed through an unconformity down from
the Snake Creek Mudstone for similar reasons, so that intervals are of constant thickness with the
exception of near the zero edges where both the Showgrounds Sandstone and Rewan Formation
were adjusted. Figure 6.1 shows typical horizons interpreted on different vintages of data, where
different seismic processing flows used resulted in non-uniformity of seismic character; itself
leading to difficulties in tying different vintages of data.
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