| Mittagong Formation | |
|---|---|
Stratigraphic range: | |
 | |
| Type | Geological formation |
| Underlies | Ashfield Shale |
| Overlies | Hawkesbury sandstone |
| Thickness | up to 10 metres (30 ft) |
| Location | |
| Location | Sydney Basin |
| Country | Australia |
| Type section | |
| Region | Mittagong |
| Country | Australia |
| Thickness at type section | 15 metres |
The Mittagong Formation is a sedimentary rock unit in the Sydney Basin in eastern Australia.[1]
Laid down in the Triassic Period, it may be seen as an interval of interbedded fine-grained sandstone and shale between the Ashfield Shale (above) and the Hawkesbury sandstone (below). The maximum thickness around Sydney may be ten metres.[2] Near Town Hall railway station, the formation is 8 metres thick. In the type area at Mittagong it is 15 metres thick.
In northern Sydney it can be seen in several areas, such as West Pymble[3] and Mount Ku-ring-gai.[4] This rock formation is associated with the critically endangered Sydney Turpentine-Ironbark Forest.[5]