|Nimbin Rhyolite (front), Mt. Warning (right), Binna Burra Rhyolite (distant)|
Actually, the rocks have not changed but for some reason I cannot fathom (like most of the other points raised above) the rocks often have different names but many have the same ones. Rocks of the Mesozoic Clarence-Moreton basin have the same names, rocks of the Palaeozoic basement have the same names, but rocks of the Lamington Volcanics are named differently. You can stand on the Lismore Basalt and take one step into Queensland and you are on the Beechmont Basalt. Suffice to say it can be confusing. So, based on Duggan and Mason (1978) here is a table to show what the rocks units in the Lamington Volcanics are called in either state:
It is also important to note that stratigraphy is often refined once more is known about rock units. A good example is that some authors such as Cotter 1998 dispute the existence of the Homeleigh Agglomerate Member which is considered part of the Nimbin Rhyolite. Also the Mount Gilllies Rhyolite has been renamed the Mount Gillies Volcanics, Therefore a different unit called the Georgica Rhyolite would be an equivalent of the Mount Gillies Volcanics.
I know I’ve said it elsewhere, but geology is not usually too difficult. The worst part is the nomenclature. I think this is a good example. What do you think?
*Cotter, S. 1998. A geochemical, Palaeomagnetic and Geomorphological Investigation of the Tertiary Volcanic Sequence of North Eastern New South Wales, Masters Thesis, Southern Cross University.
*Duggan, P.B., Mason, D.R. 1978. Stratigraphy of the Lamington Volcanics in Far Northeastern New South Wales. Australian Journal of Earth Sciences V25.
*McElroy, C.T. 1969. The Clarence-Moreton Basin in New South Wales. In Packham, G.H.(ed) - The geology of New South Wales. Geological Society of Australia. Journal V16.