Seismic reflection evidence for the evolution of the Camden Syncline and Lapstone Structural Complex, central Sydney Basin, Australia

Abstract

The Camden Syncline and the Lapstone Structual Complex are two major geological features of the central Sydney Basin. We have interpreted over 500 km (45 lines) of an unpublished recenty reprocessed seismic dataset as a means to elucidating the evolution of both features. Major horizons observed in the seismic data have been described and correlated with significant tectonic events that shaped the formation of the greater Sydney–Gunnedah–Bowen Basin; namely Early Permian extension, mid-Permian passive thermal subsidence and Late Permian to mid-Triassic foreland loading. Horizon mapping shows that the Camden Syncline is a broad north-northeast plunging structure whose western limb is truncated by the north–south trending faults and folds of the Lapstone Structural Complex. Furthermore, isochron maps reveal that the Late Permian to mid-Triassic sedimentary succession thickens towards the axis of the Camden Syncline, thus confirming it's role as a depocentre during this period of basin evolution. No abrupt thickening is observed in the Late Permian to mid-Triassic sedimentary succession in the vicinity of the Lapstone Structural Complex indicating that the Lapstone Structural Complex was formed subsequent to the deposition of the Permian–Triassic Sydney Basin sedimentary succession. Furthermore, our interpretation of the reprocessed seismic data confirms that the major structural style of the Lapstone Structural Complex is that of west dipping reverse faults and east facing monoclines.

Key Words:

• basin evolution
• Camden Syncline
• isopach map
• Lapstone Structural Complex
• seisimc reflection data
• Sydney Basin

Acknowledgements

We thank Joe Choudhury and Andrew Lukas for access to the seismic data from Sydney Gas Ltd (now part of AGL Ltd) and for their interest in this project. Andrew Bray is supported by a postgraduate scholarship from CRC Mining. Chris Fergusson acknowledges the training and data acquisition for ArcGIS programs that was provided by Heidi Brown (School of Earth and Environmental Sciences, University of Wollongong). Funding to Chris Fergusson was provided by the GeoQuEST Research Centre (University of Wollongong). We thank Dan Clark and Jenny Totterdell for their reviews that have improved the final manuscript.