The State Circle Shale was named by Öpik in 1958. It is named after the street where it was described. Its age is Llandoverian. Its lithology is shale, mudstone, siltstone and minor sandstone. In the type location there is about 60 metres of non-calcareous sandy shale and dark grey shale with beds of fine-grained sandstone. Between Kings Avenue and Commonwealth Avenue, there is a good outcrop on State Circle, consisting of buff-coloured laminated siltstone and shale with fine sandstone beds contorted by slumping. Its top is an unconformity, with Camp Hill Sandstone lying on top. There is probably up to 200 metres thickness of this shale. The shale was deposited in the deep sea as turbidites. It can be found in Yarralumla, Parkes, Acton, north and south of Black Mountain, and from Lawson, to Crace and Ngunnawal.