Geology of the Maydena Range

The oldest rocks of the area are the (?) Precambrian
pyritic quartzites with interbedded conglometates.
These are overlain by 60 m of pebbly
siltstone, about 300 m of ferruginous sandstones
and siltstone and 300 m of quartzitc and siltstone
which represent a stable tectonic environment
of pre-Ordovician age. The pre-Ordovician
rocks were folded before deposition of the Ordovician
sediments.
The Arenigian Florentine Valley Mudstone is
at least 140 m thick and is overlain by the lower
600m. of the Gordon Limestone, the upper parts
of. Which are faulted out.The Lower•Upper
Middle Devonian .Tabberabberan Orogeny resulted
In the formation of north-westerly plunging folds.
A complete flatly dipping Permian sequence
begins with at least 220 m of Lower Sakmarian
Wynyard Tillite, which was derived from a glacier
With a north-westerly origin .This. is overlain by
137 m of Woody Island Siltstone, 9.2 m of
fossiliferous siltstones, 3.7 m of Darlington Limestone,
and 32 m of Bundella Mudstone all of
which are marine. These are overlain by the
freshwater sedimennts of the Mersey Group (with
a maximum thickness of 52 m), followed] by a
marine sequence composed of 80 m of the Cascades
Group, 64 m of the Malbina Siltstone and
Sandstone and about 150 m of the Ferntree
Group. The terrestrial Cygnet Coal Measures
4.4 m thick, is the top Permian formation. The
Permian rocks form a very shallow east plunging
syncline.
Three hundred and twenty metres of freshwater
Triassic sediments disconformably overly the
Permian rocks and are intruded by a Middle
Jurassic dolerite sill. Normal faults, with down throw
to the east -north-east and to t he northwest
and probably associated with the formation
of the Tertiary Derwent Graben, cut the older
rocks. Dolerite talus slopes developed as periglacial
material during the Pleistocene.