The Pilbara bioregion, where the Proposal (Mining Area C/South Flank) is located, is situated in the south-eastern comer of the Pilbara Craton. The cratonic basement comprises Archaean granite-greenstone and is unconformably overlain by the late Archaean to Early Proterozoic deposits of the Hamersley Basin. The Hamersley Basin can be divided into three stratigraphic groups: the Fortescue, Hamersley and Turee Creek groups. Of these groups, the Fortescue and Hamersley groups outcrop in the immediate area Mining Area C.

The Hamersley Group is seen throughout the Hamersley Basin and forms the outcrop of Mining Area C. It is a sedimentary sequence comprising banded iron formations (BIFs), shales and dolomites with minor felsic volcanics and intrusive dolerite dykes and sills. The group contains both the Brockman and Marra Mamba Iron formations, which together host most of the known major iron ore deposits in the Pilbara region. The six lowermost formations of the Hamersley Group that exist within the area are listed below in order of increasing age:

1. Weeli Wolli Formation.

2. Brockman Iron Formation. Ore mineralisation from the Packsaddle Range deposits is contained within the Brockman Iron Formation, composed of a sequence of interbedded Banded Iron Formation, shales, siltstones and cherts. The four members comprising of the formation are:
- Yandicoogina Shale Member (shale and BIF);
- Joffre Member (BIF with minor shale bands);