Bringelly Shale

Bringelly Shale
Stratigraphic range:
Exposed Bringelly Shale at Greystanes, Australia
Type	Geological formation
Unit of	Wiannamatta group
Underlies	Ashfield Shale
Overlies	Hawkesbury sandstone, Minchinbury Sandstone
Thickness	up to 60 metres (200 ft)
Lithology
Primary	Shale, claystone, siltstone
Other	Sandstone
Location
Location	Western Sydney
Region	LGAs of Liverpool, Camden, Wollondilly, Penrith and Fairfield
Country	Australia
Type section
Named for	Bringelly

Bringelly Shale is a component of the Wianamatta group of sedimentary rocks in the Sydney Basin of eastern Australia. Formed in the Middle Triassic Period, it has an extensive outcrop in the western parts of Sydney and occupies around one third of the Sydney sheet. Occupying much of the Cumberland Plain, the shale has its greatest geographical extent at Bringelly (its namesake), near the suburb of Liverpool. Featuring sandstone lentils that alternate with claystone and siltstone, Bringelly Shale forms the topmost layer of the Wianamatta Group and is the youngest Triassic sedimentary rock unit in the Sydney Basin.

In the late 1970s, the Bringelly Shale was redefined to include all Wianamatta Group sediments above the Minchinbury Sandstone. Consequently, substantial sandstone units—up to 30 metres (98 ft) thick but of limited lateral extent, typically representing channel or point bar deposits—are now treated as members of the Bringelly Shale. These include the Potts Hill Sandstone, Razorback Sandstone, and Mt Hercules Sandstone. Bringelly Shale was deposited in large swamplands and winding estuarine and alluvial channels.