Wianamatta Group

Deep and large clay deposits of this formation are able to collect groundwater; however, if they are at or near the surface, salted dry land may form as the water evaporates.

[3] The Wianamatta Group has been inferred to represent a cycle of basin infilling associated with the migration of a large delta front from west to east.

The Ashfield Shale was deposited in a low energy marine environment and preserves laminated silty sediments.

The Bringelly Shale was deposited in a swampy alluvial plain with meandering streams flowing from the west forming discontinuous beds of sandstone.

[2] Weathering of the shale units produces a rich clayey soil, often with poor drainage, such as that in the Cumberland Plain.