Summary:
The Project is located on the western limb of the Bowen Basin, a north-south trending Early Permian to Middle Triassic geological basin. Comprised of a sedimentary sequence of Permo-Triassic clastics, which attain a maximum thickness of 9,000 metres (m) in the depocentre of the basin, the Taroom Trough, the Bowen Basin is vast and covers an area of approximately 200,000 square kilometres, from Collinsville in the north to Rolleston in the south.
Divided into a number of tectonic units which comprise north-north-west to south-south-east trending platforms/shelves, separated by sedimentary troughs, the major structural features of the Project area include the Collinsville Shelf to the north and the Nebo Synclinorium 2 to the east.
Folds within the Basin are gentle and generally the results of drag on thrust faults along the eastern boundary of the basin. The boundary between the Collinsville Shelf and the adjoining major axis of deposition, the Nebo Synclinorium of the Taroom Trough, is indicated by a major thrust fault, the Jellibah Thrust Fault (URS, 2012). Limited regionally significant fault zones or structures differentiate the sediments of the Collinsville Shelf from the tightly folded and intruded sediments of the Nebo Synclinorium (Elliot, 1989). Summarised, the sequence comprises:
- Middle Permian Back Creek Group (basement);
- the Late Permian Blackwater Group sediments (and coal measures);
- unconsolidated Tertiary sediments;
- unconsolidated Quaternary alluvium sediments.
The Tertiary Duaringa Formation is also present, but limited, in the region.
The sediments across the Project are generally undisturbed and have a gentle regional dip of 2° to 5° towards the east. Faults are mapped within the existing Saraji Mine, which are typically minor; steepen locally to approximately 9° to 10°. The Saraji South Fault is located south of the site, near Phillips Creek; a high angle, north-north-west trending normal fault, throws have been mapped between 10 and 50 m (AGE, 2011). The Downs Creek Fault is a north-north-west trending normal fault with a maximum throw of 60 m and is located south of the Project area, near Lotus Creek Road.