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Main Range Volcano | John Seach
SE Queensland/NE New South Wales
Australia
27.9 S, 152.4 E
central volcano province
Extinct volcano
Main range volcanics cover a large area from Urbenville in NSW 200 km North to Kingaroy in Queensland.
The eastern edge of the Main range is a steep escarpment, part of
the Great Escarpment, with peaks up to 1,100m above the broad valley
to the east. The upper part of the scarp consists of cliffs of
Basaltic rocks. Lower down, talus slopes, in many places, obscure
the lower members of the volcanic sequence and the contact with the
underlying Mesozoic sedimentary rocks.
The Great Divide is close to, or coincides with, the top of the
escarpment. West of the Divide the original Basaltic tableland has
been strongly dissected by streams, leaving only ridges and a few
small remnants between them. The volcanic rocks, dominantly Basalts,
have a total thickness of up to 900m beneath the highest points on
the Divide; they have been divided into two formations of almost
equal thickness.
The lower formation, the Governors Chair Volcanics, contains
well-marked members interbedded with the Basalts. The upper
formation consists entirely of Basaltic rocks and is widespread over
an area of 160,000ha. The trachytes of the lower formation exhibit
outstanding cliff faces at The Steamers, in Emu Creek and at Mount
Castle on the escarpment. The Main Range, although on the whole
drier than the McPherson Range, has at least three major waterfalls.
The Main Range volcanics are of late Oligocene to early Miocene age.
National parks covered include:
Tooloom, Main Range, Bunya Mountains.
Main Range Volcano Eruptions
23 to 27 million years ago