Tertiary Groups . 
85 
CHAPTER VIII. 
Tertiary groups . Oligocene — localities , fossils . Miocene — 
marine * localities , character ; lacustrine deposits , 
quartzites . Flmiatile deposits . Miocene fossils . . O&fer 
Volcanic Rocks — character , localities. 
Tertiary. 
Formations of Tertiary age arc very extensively developed in 
Victoria, occupying nearly one-half the area of the colony ;• they 
are geologically divisible with tolerable certainty into three prin- 
cipal groups, viz., Lower Tertiary (Oligocene), Middle Tertiary 
(Miocene), and Upper Tertiary (Pliocene), 
Lower Tertiary (Oligocene). 
The Victorian Lower Tertiary beds, which the term Oligocene 
lias been employed to designate, really belong to the uppermost 
portion of the Lower Tertiary group, and appear to occupy an 
intermediate position between the Eocene and Miocene. Of the 
Eocene, or Lower Tertiary strata of European and American 
geology, there appear to be no equivalents exposed in Victoria 
whatever may be concealed beneath newer formations, and the beds 
classed as Oligocene are here the oldest known members of the 
Tertiary series. They are exposed close to the sea-coast in a few 
localities of very limited extent, of which the best known are as 
follows: — Portion of the coast between the mouth of the Gelli- 
brand River and Port Campbell ; on the coast to the west, and also 
about a mile inland on the east side of the Aire River a few 
miles north-west from Cape Otway ; in a foAv places in the Geelong 
district, and on the east coast of Port Phillip, near Mount Eliza 
and Mount Martha. 
These beds are exposed inland, near the junction of the Grange- 
burn and Muddy Creeks, a few miles west from Hamilton ; also, I 
understand, near Violet Town, to the north of the Main Divide ; 
and undoubtedly underlie large areas iu the western and northern 
districts. Lithologically, they consist principally of blue or grey 
clays, sometimes stiff and tenacious, sometimes sandy, with patches 
composed almost entirely of more or less fragmentary shells, 
loosely held together by sandy clay. Calcareous septarian nodules 
are common on the cast coast of Port Phillip, in Oligocene clays, 
which Mr. Selwyn describes as closely resembling the Eocene 
strata of the Hampshire and London basins. In all places where 
the beds are exposed, they are rich in fossils, among which are 
some gigantic forms of Volutes and Cyprcea (cowry). The forms 
