Re: Roots in coal?

From: Bill Payne <bpayne15@juno.com>
Date: Sat Jan 03 2004 - 08:57:50 EST

Hi Kevin,

On Tue, 30 Dec 2003 20:55:30 -0700 "Kevin Sharman" <ksharman@pris.bc.ca>
writes:

You [KS] wrote: I have shown you pictures of roots below the seams,
about which you stated (Dec.18): “I agree that the radiating roots in
your last photos are, as far as I can tell, "identical to ones that grow
in place today."” Your objection to these demonstrating insitu growth is
that there are not enough of them. Then you quote a paper supporting my
position: "Trees in the mixed peat-swamp forest and pole forest...have
spreading, buttressed, and prop roots, which are generally confined to a
root mat 50-80 cm thick at the top of the peat and do not penetrate to
the deeper peat or mineral sediments below thick peat." (my emphasis).

I [BP] reply: I disagree that the preceding quote supports your
position. I'll send you off-line a photo (if others want to see the
photo, please contact me offline) from another paper (by Pfefferkorn et
al, 2001) that shows a tangled mass of roots from a modern swamp. This
photo shows how I envision that the root mat beneath a peat swamp should
look. We agree that if you have a meter or so of peat accumulated from
shrubs followed by swamp trees, there should be no tree roots in the
mineral substrate - the tree roots should be confined to the shrub-peat
mat. However, when the shrubs became established, and during the time
required to produce a meter of peat from shrubs, they should have formed
a mat of entangled roots similar to what we see below the swamp trees in
the Pfefferkorn photo. I wouldn't think we would be able to distinguish
individual roots below a coal seam like those we see in your photos.

Take a look at the peat at http://www.atthepeats.com/diary.htmpeat. This
peat is completely root-penetrated and shows no structure which might
lead to banding. This is why I say I don't see how we can get banded
coals from this structureless mass of peat. Does your model include
transformation of structureless, intensely root-penetrated peat into
banded coal? I think you said the structure of cells may be lost during
coalification, but the formation of bands from a root mat seems to
require some fundamental reorganization to form interbedded organics and
inorganics (to form laterally extensive partings).

[KS] I have also shown you references to roots within these coal seams.
Here’s one more for good measure: From Lamberson et al (1996): “ As
observed during the standard point count analyses (no quantitative
analysis was done), fusinite and semifusinite represent discrete plant
organs, principally stem and root wood, leaves, and bark of gymnosperms
as well as the leaves and rhizomes of ferns.” I have explained
petrographically how the characteristics of the original vegetation are
obscured and destroyed during coalification. It appears that you will
not accept this explanation. You are objecting to it because it doesn’t
satisfy the criteria you have laid out for you to accept this as insitu
coal. I submit that these seams are insitu based on what we’ve seen so
far. You are welcome to reach your own conclusions about this.

[BP] Disarticulated root fragments in coals don't bother me. What I
would like to see though for a coal seam to be in situ is root masses
similar to those in the photo I am sending to you. Are you saying that
this tangled mass of roots could become banded coal through
coalification? If so, this is the process I need to understand. To be
persuasive, you also need to include the formation of partings, which
don't typically include tree trunks or roots, in your explanation.

[KS] In other words, why do Carboniferous coals with their
characteristic vegetation accumulate in the areas they do, and Jurassic
and
Cretaceous coals with a different unique vegetation accumulate in other
areas, when you are proposing that they were all floating around
together? [snip]

Bill, you have not answered my question. Let me restate it: Suppose you
lift a mat up with a flood. You can keep it stationary or float it
around; it doesn’t matter. Directly below the Gates coals there are
~8000 meters of Phanerozoic sedimentary rocks. These are a variety of
types including deep water marine mudstones, shelf carbonates,
evaporites, turbidites, etc. None of the above rocks have coal in them.
 Why not? How do you explain the fact that only sediments characteristic
of shallow marine and non-marine environments have coal in them, if all
of the above rocks were being deposited underneath a floating mat? Until
you can come up with a plausible explanation for this, backed up with
evidence, your floating mat model will remain in the realm of
speculation.

[BP] That's an excellent question, Kevin, and one which I haven't fully
appreciated till now. The conundrum is that I see evidence, at least in
the eastern US coals, that seems to require transported deposits which
settled out of water. I freely admit to not having all of the answers,
but typically others will point to a few roots, or say there's too much
coal for a floating-mat source, or say why no deep ocean coal, or list
your comments above, and then conclude that that's the end of the
argument - coal must be in situ. I continue to maintain that we need to
address the objections that I have raised and see if we can somehow come
up with a coherent picture that incorporates your observations with mine.

[KS] If you want to challenge the “assumption” that burial is responsible
for coalification, you need to provide your own detailed model. The
relationship between rank (degree of coalification) and depth of burial
has been established in many coal basins. “Near surface coals in the
Alberta plains increase in rank toward the west-southwest (that is,
towards the foothills/ mountains region). A new model to explain this
coal rank distribution is proposed. This model relates a coal seam's rank
to its maximum (paleo)depth of burial....Progressively greater amounts of
overburden existed in a direction toward the mountains at the time of
coalification. Erosion since middle Tertiary time has removed between 900
and 1900 m (3000 and 6200 ft) of sediment; the greatest amount of removal
is in the west southwest area, where coals of higher ranks are exposed.”
Nurkowski, J.R. (1985) Coal Quality and Rank Variation in Upper
Cretaceous and Tertiary Sediments, Alberta Plains Region. Alberta
Geological Survey, Earth Science Report 85-01.

[BP] I understand that rank is related to depth of burial. When I was in
school I calculated the amount of cover which must have eroded from the
Mississippi drainage basin to fill the Gulf Coast geosyncline. I came up
with a thickness of about 1 mile of material over the entire basin to
fill the geosyncline to a depth of 50,000 feet. Glenn has a similar
calculation in his book (Foundation, Fall and Flood, p 28) and came up
with 1.03 mile (Glenn's a little more precise than I am) thickness of
sediment eroded off the continent within the drainage basin. I recently
came across a reference in a paper that said the rank of bituminuous coal
in Alabama was consistent with a burial depth of about one mile - which
is a nice concurrence with what Glenn and I did.

[KS] Early coalification can be caused by fusinitization, where the peat
is transformed either by charring, oxidation, mouldering, and fungal
attack. Fusinite is relatively resistant to chemical and mechanical
breakdown and can form particles which can be transported by water. This
has been reported in the literature; even Steve Austin’s abstract
mentions fusain clast conglomerate.

[BP] OK, as long as the fusinite can be coalified to look like the clasts
that Cross reported, which I had assumed were mainly vitrinite - but that
may not be correct. I have also heard of coal clasts above coal seams
here in Alabama. Can fusinite be coalified into vitrain?

Bill

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Received on Sat Jan 3 00:09:09 2004

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