Fossils can be found in coastal cliffs, riverbanks, road and railway cuttings, building excavations, sewer and water-pipe tunnels and trenches, and quarries. Natural outcrops are uncommon and weathered, so the best-preserved fossils often come from temporary exposures caused by human activity. Many of the brick pits and quarries that yielded fossils, such as those at Brunswick and Hawthorn, are now filled in.
The nature of the geology of Melbourne dictates the kind of fossils that can be found. The formations yielding fossils are of two broad ages: Palaeozoic and Tertiary. At Keilor in the Maribyrnong River valley, exposures of the Springfield Formation contain Early Silurian graptolites and rare trilobites. Further east around the city itself, in cuttings along the left bank of the Yarra River near the Royal Botanic Gardens, in city building excavations, in cuttings at Studley Park, and in the banks of the Moonee Ponds Creek at Moonee Ponds, exposures of the Late Silurian Melbourne Formation contain graptolites, trilobites, sea lilies and brachiopods.
The youngest Palaeozoic strata in the Melbourne district - the Early Devonian Humevale Formation, exposed in cuttings around Lilydale - contain a rich assemblage of brachiopods, bivalves, sea lilies and trilobites. Corals are found in the Lilydale Limestone in the Lilydale Quarry, the only outcrop of limestone in the Melbourne suburban area.
Tertiary sediments are widespread, particularly in the south-eastern suburbs. The oldest known are non-marine sediments of probable Eocene age under the Older Volcanics and contain leaf remains that have been collected at outcrops on Moonee Ponds Creek at North Melbourne and Pascoe Vale. Other leaf-bearing Tertiary sediments are found under basalt at Berwick.
Most of the Tertiary sediments are of marine origin. The Middle Miocene Fyansford Formation, now weathered to ironstone in many places, contains rich faunas of molluscs, corals and Bryozoa; they have been found in the Royal Park railway cutting, in cuttings and excavations at Essendon, and formerly in cuttings at Windsor and South Yarra. Unweathered outcrops, now partly covered over, occur in the shore platform at Beaumaris and at Fossil Beach, Mornington.
Lying above the Fyansford Formation is the Late Miocene Black Rock Sandstone, containing shallow-water faunas of bivalves and echinoids, best known from outcrops in cliffs at Beaumaris, but also found in sewer excavations in the south-eastern suburbs. Between these two formations is a bed with phosphatic concretions, whale bones and shark teeth exposed in the intertidal zone at Beaumaris.
The youngest fossiliferous sediments are Holocene in age, the so-called 'raised beaches' around the edge of Port Phillip Bay, such as at Seaholme, and the estuarine sediments of the Yarra and Maribyrnong valleys, usually only known from shallow temporary excavations.