Re: Roots in coal?

On Thu, 18 Dec 2003 06:13:59 -0700 "Kevin and Birgit Sharman"
<ksharman@pris.bc.ca> writes:

> (referring to image analysis of a block sample of the seam) "A
> branched gymospermous root structure is present in Fig. 11, and has
been
> pyrolysed to fusinite." From the caption to the figure: "Enlargement of
area
> shown in a) showing transeverse section of root structure. Small cell
size and
> lack of definition in annual growth pattern indicative of root origin".
 

It sounds like this root is a rare occurrence. If this were from a
swamp, shouldn't there be roots throughout the coal? Also, if this coal
were "metamorphosed" as you indicated previously during gelification, how
is it that this root is still defined in the inertinite groundmass?
 
> The above example may or may not
> satisfy your criterion for cross cutting roots, since we can't say with

> certainty what the inertinite groundmass represented in the figure is.

We need to see roots everywhere, like in modern swamps. Not just the
occasional isolated root.
 
> Incidentally, I recall you emphasized in an earlier post that
> abundant bark layers in Carboniferous coals supported an model of
floating mats
> shedding bark by abrasion (please correct me if I'm wrong on this).

Since the lycopods were apparently nearly hollow to begin with, they may
have become hollow soon after uprooting and just settled on the bottom
without any abrasion.
 
> A couple of questions for you. For the Cretaceous seams in the
> photos:
>
> What floating mat model are you favoring - a "grounded mat" model or
> a "shedding mat" model? This has bearing on your explanation of the
> roots.

The "shedding mat" model seems to best fit the data of which I'm aware
with reference to the Carboniferous coals in the eastern US. This model
would explain rootlets preserved with but disconnected from the axial
roots (an apparently common occurrence), acid water beneath the floating
mat causing flocculating of clays from turbid water to form the
underclays beneath many (but not all) coals, the horizontal layering of
bark to form banding, and splits of coal off the bottom (leaders) and off
the top (riders) of the main seam.

What problems do you see with this model?
 
> Are you proposing a marine setting for these coals?

In some cases, yes, based upon the association of marine fossils,
carbonates and high sulfur (which I assume from my reading is from marine
influence). In other cases the coal may have settled in predominately
fresh water. This flood model would require that all of the waters were
not uniformily mixed. I also infer that the mats of vegetation were not
mixed, but isolated stands of vegetation maintained their unique mix of
plants after the flood took them into suspension.
 
> Are you sticking with your criteria outlined in you Mr. 25, 1999
> post for falsifying the floating mat model (copied below)? Anything to
add?
>
> "to falsify the floating mat model, I would like to see
> intensely and deeply rooted underclays with little or no
> interbedded structure remaining, a gradational contact between the
underclay
> and coal, roots connecting to the last generation of stumps in the
> swamp, and the last generation of stumps still standing in the coal
where they
> grew."

I appreciate your taking the time, Kevin, to read back into the archives
for this. I also appreciate your non-combative spirit. In general, the
above looks okay. I know that there can be gradational contacts between
coal and underclay, and this would fit either model. Occasionally we do
see standing stumps on top of coal and I've seen one beneath a coal seam,
but these seem to be the exception rather than the rule.

One thing I would add is partings within coals which seem invaribly to
have few or no plant macerals. I was going to ask you if you have
partings in your Canadian coals, and if so, do they preserve the stems of
the trees that were growing in the swamp when the parting was deposited,
and do they show roots from the trees that would have grown on top of the
parting when the swamp was re-established? You said everything got
metamorphosed in the coal seams, but I assume the structures would be
preserved in the partings as they are in the sandstone beneath the coal
in your photos. Can you describe the partings?

Aonther criterion is fecal pellets which are abundant in in situ peat
deposits but rare in transported peat mats. It's my impression that
fecal pellets are not common in coals.

How do your Canadian coals compare to the criteria?

Bill

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Received on Sat Dec 20 00:11:57 2003