ABSTRACT
The Brighton Group comprises up to 40 m of flatlying to gently dipping, variably iron-stained and cemented, mostly sandy sediments of Late Miocene to Early Pliocene age. Beneath the Newer Volcanics west of the Maribyrnong River, the Brighton Group consists of fairly uniform, poorly bedded, red-brown silts, sandy silts and clayey silts with occasional gravel bands. Substantial additional information on the subsurface distribution of the Black Rock Sandstone is provided in unpublished reports on a number of large Board of Works tunnels in the Brighton-Cheltenham Block. In general, by increasing the dispersal of limonite cement, weathering has increased the hardness and stability of the Brighton Group sediments. Except where overlain by thick Quaternary deposits, the Brighton Group, especially the Red Bluff Sands, is the substratum for large engineering structures throughout much of the Brighton-Cheltenham block. The sands and sandstones of the Brighton Group have moderate to good porosity and permeability, and contain a system of unconfined to weakly confined aquifers.
