 Glacial dropstones are found in the interbedding, suggesting Cryogenian age, however carbon isotope results suggest Ediacaran age instead.Gravity and magnetic studies indicate that this sort of dolomite (dense and non-magnetic) underlies Hobart and Bruny Island in a north–south strip, and also in a region west of Hobart.The Cape Sorell Block is a region of metamorphosed sediments from the Mesoproterozoic, to the south of the west end of Macquarie Harbour.