Stigmaria are roots was Re: The 'in situ' theory of coal

James Mahaffy (
Wed, 31 Mar 1999 20:46:40 -0600


Since this thread has been on ASA, I am responding just to that list and
not acg. ASA is a bit nosier list and there is no reason for both
lists, since most of the posts have not been on ACG.

c.g. winder wrote:
> Allow me to add an historical perspective .
> This theory was proposed by William Logan who studied the Carboniferous
> south Wales coal beds which he mapped in the 1830's. His paper was
> published in the bulletin of the Royal Institute of South Wales, 1840,
> located in Swansesa. Logan, as the manager of a copper smelter plant,
> recognized he needed a guaranteed supply of coal, and an estimate of the
> Joggins Nova Scotia, where he found the same Stigmaria, that were present
> in Wales. In his view the Stigmaria and other vegetation was the source of
> the vegetation which formed the coal beds. He proposed the in situ
> and rejected the 'drift' theory, which was associate with the Flood.

Just a bit of a paleobotanical correction. Stigmaria is not the whole
plant that makes up the coal but only the roots of several different
arborescent (tree) lycopods. The names of the whole plant are usually
named after the stem genera and are mainly Lepidophloios, Lepidodendron,
and Sigillaria [although Bill DiMichele, the best North American lycopod
worker, has split the lycopods into a number of other genera]. As is
common in paleobotany you often see only parts of plants and different
organs of the same plant get different names. Back when Logan was
looking at the coals, the plant material that could readily be seen
would be Stigmaria in the roots (and probably also in the roof shales)
and compressions and impressions in the roof. Thin sections
(petrography) or slices of coal - balls (calcareous nodules of peat
preserved in the coal seam [the source of most of our information about
these plants) weren't being studied yet.

I just didn't want anyone going around saying the coals were mainly made
of roots. There is a lot of Stigmaria and other roots in the peat but a
lot of the vegetation matter is stem and leaves in various states of

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