ABSTRACT: Controls on Sandstone Distribution and Faulting in Permian Moranbah Coal Measures, Bowen Basin, Australia

Esterle, J. S., G. LeBlanc Smith, and J. Yago , CSIRO Exploration and Mining, Brisbane, Australia

Mine-scale drilling data combined with high wall exposures in coal mines provide high resolution data sets from which to determine the geometry and lateral facies associations of sandstone bodies and of structure. The mine scale variability of sandstone-dominated channel systems was investigated from drill hole geophysical records and mine high wall exposures over a 40 x 10 km area across 3 leases in the Permian Moranbah Coal Measures (MCM), western limb of the Bowen Basin, Australia. A 3D subsurface model was compiled for a ~200m vertical of Permian section. The resulting model shows the interplay between structure, compaction, sedimentation and peat accumulation commonly observed in coal measure strata. Thick interburdens between seams are successively offset up section. However, channel sandstone facies within these intervals tend to track and stack over similar courses, possibly due to basement controlled faulting. Sandstones occur as 2 types of channels: broad (>3km), thick (>30m) amalgamated low sinuosity channels trending SSW; and narrow (<500m), thick (>25m) ribbon shaped channels which are oblique to the main channel systems. Sandstones also occur as broad, thin to thick (<5 or >10m) irregularly shaped sheet to lobate sandstones and as thin interbeds in the finer grained rocks. The distribution of sandstones and finer grained lithologies are interpreted as low sinuosity distributary channels and splay- floodplain complexes. The position of massive sandstone channels controlled the distribution of faulting during subsequent deformation.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia