The Relationship Between Mapped Rock Units And The Stratigraphic Subdivision Of The Willyama Supergroup In Key Areas Of The Broken Hill Block

The Early Proterozoic metamorphic rocks of the Broken Hill (BH) Block have been recently subdivided into sixteen formations and four groups (Willis et al., 1983b, Stevens et al., 1983). This stratigraphic subdivision has relied upon recognition of distinctive mapped rock units and "associations" of mapped rock units, which characterize particular lithostratigraphic units. The rock units and rock unit associations define local ordered sequences which can be compared and correlated, thereby establishing the stratigraphic succession. In the Clevedale homestead, Thackaringa, BH City, Bores Mine-Freyers mine, Silver King mine, and Brewery Well areas, coherent stratigraphic successions have been interpreted. These areas illustrate the regional variability of the stratigraphic succession and facies changes within individual stratigraphic units. Stratigraphic type sections are located in the Thackaringa, Bores Mine-Freyers mine, Silver King mine, and Brewery Well areas. The principles of stratigraphic interpretation applied in the BH Block can be used in other areas of Willyama Supergroup outcrop such as the Euriowie, Olary and Mount Painter Blocks. The general technique may also have applicability to other highly deformed and metamorphosed terrains.