Primary reef framework of domical and digitate stromatolites. Flanking deposits are bryozoan and palmatozoan grainstones and packstones.

From Webby:
Localized stratigraphically within the Goldwyer Formation, of probable early-mid Darriwilian age, and occupy restricted sites immediately adjacent to a major, intra-basinal fault zone (Admiral Bay Fault Zone). Four separate occurrences of these linear-shaped, microbial-dominated reefs are recorded along the main Admiral Bay fault line over a distance of 16 km. They vary from 500 m wide and 330 m thick to 200 m wide and 25 m thick, and at least one is more than 1 km in length. The reefs exhibit a primary reef framework of domical and digitate stromatolites. Flanking deposits are bryozoan and pelmatozoan grainstones, and packstones. The fault system which defines the northeastern margin of the Willara Sub-basin, was apparently active intermittently through Early-Middle Ordovician time. McCracken et al. (1996) suggested that uplift of the footwall side of the main fault produced a narrow, raised, linear belt along the line of the fault, providing suitable shallower depositional conditions for localized reefal growth. The timing of uplift is possibly early Darriwilian. These reefal masses were subsequently fractured by renewed phases of faulting that facilitated movement of mineralizing solutions and extensive alternation of the host rocks, with the emplacement of the Mississippi Valley-type, lead-zinc mineralization.