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.