Mittagong FormationThe Mittagong Formation is a sedimentary rock unit in the Sydney Basin in eastern Australia.FormationLaid down in the Triassic Period, it may be seen as an interval of interbedded fine-grained sandstone and shale between the Ashfield Shale and the Hawkesbury sandstone. The maximum thickness around Sydney may be ten metres. Near Town [Hall railway station, Sydney|Town Hall railway station], the formation is 8 metres thick. In the type area at Mittagong it is 15 metres thick.WhereaboutsIn northern Sydney it can be seen in several areas, such as West Pymble and Mount Ku-ring-gai. This rock formation is associated with the critically endangered Sydney Turpentine-Ironbark Forest.