Port Phillip-Westernport Basin hydrogeological inventory

This Port Phillip-Westernport Basin dataset contains descriptive attribute information for the areas bounded by the relevant spatial groundwater feature in the associated Hydrogeology Index map. Descriptive topics are grouped into the following themes: Location and administration; Demographics; Physical geography; Surface water; Geology; Hydrogeology; Groundwater; Groundwater management and use; Environment; Land use and industry types; and Scientific stimulus.

The Port Phillip and Westernport basins are small, shallow sedimentary basins located in south-central Victoria, formed during the Late Cretaceous rifting of Australia and Antarctica. They share similar stratigraphy with nearby basins. The Port Phillip Basin is bounded by the Selwyn and Rowsley Faults to the east and west, while the Heath Hill Fault marks the eastern boundary of the Westernport Basin. Both basins have pre-Cenozoic basement rocks comprising folded and faulted Paleozoic metasedimentary rocks and granites from the Lachlan Fold Belt.

The Port Phillip Basin's stratigraphy includes Maastrichtian to Cenozoic sedimentary units with intercalated volcanic rocks. The main depocentres are the Sorrento Graben, Ballan Graben/Lal Lal Trough, and Parwan Trough. Notable formations are the Yaloak and Werribee formations, with coal-bearing strata and marine sediments.

The Westernport Basin has coastal sediments and volcanic deposits from Paleocene to Holocene. It experienced marine transgressions and regressions due to sea-level fluctuations. Fault movements in the late Pliocene and early Pleistocene formed a fault-bounded depression centered on the Koo Wee Rup Plain. The main units are the Childers Formation, Older Volcanics, Yallock Formation, Sherwood Marl, and Baxter Sandstone.

Both basins have Quaternary sediments, including Pleistocene eolian sand sequences, Holocene alluvial and paludal clays, and fluvial sediments in valleys and palaeovalleys. The Port Phillip Basin contains distinct phases of terrestrial and marine deposition, while the Westernport Basin has Eocene volcanism and marine sediments. These basins are important geological features in the region, with various formations representing millions of years of geological history.