Re: coal again! (was asteroids and energy)

James Mahaffy (
Fri, 19 Mar 1999 19:46:30 -0600

Jonathan Clarke wrote:

> I have seen stumps in coal in the Eocene and Miocene lignites of Western

> Australia and Victoria, respectively. So they do exist, although are not
> very common. Interestingly, studies of modern peat mounds and the ecological
> succusion of ancient ones shows that the climax community of such ombrogenous
> bogs (wonderful word!) is often dominated by mosses, with few trees. "Swamp
> forest" occurs only in the the early stages of development.

If I am not mistaken and, I looked at it fairly recently, the tropical
ombrogenous peats of Sarawak and Brunei, which are perhaps the best analoges for
the Carboniferous coals are still dominated by trees but more stunted trees and
more open vegetation. In any case in these swamps there is still woody vegetation
in the oldest raised peat mounds.

I might also caution against seeing most coals as a simple successional
sequence. The story does not appear to be that simple. It is true that one of
the better earlier ecological studies by Smith (1962) of some Carboniferous coals
(from Namurian to Westphalian B) showed bottom of the coal seam as a bright coal
dominated by spores of a larger lycopod tree (Lycospora) and the top a dull coal
(duritic) dominated by densospores toward the top of the seam. That almost fits
with Jonathan Clarke's generalization, but a bit higher in the section
(Westphalian D), where I did my palynological work, Densospores are not found and
the whole seams up to the very top are generally bright (vitrain) coals. There
are some differences in vegetation at the top of the coal seam but it is changes
to other tree forms of lycopods and not small herbaceous forms.

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