Mapping a coastal transition in braided systems: an example from the Precipice Sandstone, Surat Basin

ABSTRACT

The Precipice Sandstone is traditionally interpreted as a braided fluvial deposit that transitions upwards into meandering channel deposits responding to a rise in base level that eventually deposits the overlying alluvial to lacustrine Evergreen Formation. This study found sedimentary evidence of tidal to marine influence within the Precipice Sandstone coincident with avulsion and diversion of the system from southward to northward-flowing channels as the system was transgressed. The north-flowing channels are interpreted to debouch into a shallow restricted marine embayment with tide and wave influence, which provides an alternative insight into this unit and suggests a Lower Jurassic north or northeasterly marine connection. The Precipice Sandstone is a regional aquifer, in places hosts hydrocarbons and has been considered as a storage unit for CO₂ geosequestration. Outcrop analogues can provide geometries to accompany facies interpreted from sedimentary structures that are observable in core, to assist in characterising reservoir heterogeneity.

KEYWORDS:

• Lower Jurassic
• Precipice Sandstone
• facies analysis
• paleogeography
• coastal transition
• braided

Acknowledgements

N. Hall and R. Heath are thanked for internally reviewing the project. M. Ghinassi and M. Blum are thanked for the constructive discussion. A. La Croix is here greatly thanked for a substantial revision and improvement of the manuscript. B. Jones and an anonymous reviewer are thanked here for their helpful suggestions in the revision stage of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors

Additional information

Funding

The authors wish to acknowledge financial assistance provided through Australian National Low Emissions Coal Research and Development (ANLEC R&D) [grant number 7-0314-0228]. ANLEC R&D is supported by Australian Coal Association Low Emissions Technology Limited and the Australian Government through the Clean Energy Initiative.