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Dear Thanks for your efforts, particularly Hermann Pfefferkorn and Steve Carey. So, apart from the
evolutionary constraints which precluded coal formation prior to the Devonian,
it seems that the important feature is the water table height and the
topography, rather than temperature. Most of the Carboniferous coals were
apparently tropical in their origin, but the huge coal deposits of Eastern
Australia (Sydney Basin, Gunnedah Basin, Bowen Basin) were deposited in a climate
that was as cold as a mother-in-law’s kiss, as most recent plate
reconstructions have Australia at about 60 degrees south of the equator at that
time; hardly a tropical paradise. The surprising thing with petroleum source rocks (at least
on this side of the planet) is that up until the Permian all of those either identified
by geochemical correlation or other means are marine shales, whereas from the
Permian onwards most are of fluvial, lacustrine or paludal depositional
environments, mostly with a component of coal. Trouble is, up until recently,
not many people considered coal as a source rock for anything other than
methane, although this is beginning to change. John ----------------------------------------------------------------- Eastern and Onshore Petroleum GEOSCIENCE Street Address: ABN 80 091 799 039 |
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