Re: Roots in coal?

From: Kevin Sharman <ksharman@pris.bc.ca>
Date: Mon Jan 05 2004 - 09:06:07 EST

  ----- Original Message -----
  From: Bill Payne
  To: ksharman@pris.bc.ca
  Cc: asa@calvin.edu
  Sent: Saturday, January 03, 2004 6:57 AM
  Subject: Re: Roots in coal?

  Hi Bill,

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

  [KS]: 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).

  [BP]: 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.

  {KS replies} Bill, your reference talks about lack of tree roots below the peat. Does it say anything about other roots? Unless it does, we can't use it to judge expected shrub root density below the coal in the photos, and we are back to comparing your expectations with what we see in the photos.

  [BP]: 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 replies} I will re-repeat myself and state that "I repeat my contention that gelification destroys and masks the original plant structure. The banding in coals is from the original vegetation types and the coalification history of the peat. The same parent vegetation can make layers of different macerals depending on its history of transformation into coal."

   

  "This is an explanation of what happens to veg material as it coalifies, and where the whole logs, roots, stumps etc. went. If there weren't processes like this going on, we would see all the roots that were in the original peat."

   

  Bill, coalification can and must change structureless peat into banded coal. In your model, the accumulated veg material is a pile of stems, logs, leaves, and yes, even roots. Does the coal seam look like that today, allowing for compression? Do we see the coal as a mass of individual flattened stems, logs, leaves, roots? NO, it's banded. So, whatever model you consider, the original vegetation must be changed to banded coal.

   

  Stach (1982): "In the soft-brown coal stage, many stumps and stems can still be seen in the seams with the naked eye, when they are termed xylite".

   

  Lower rank coals display abundant plant structure, including roots. Stach (1982): "In the soft-brown coal stage, many stumps and stems can still be seen in the seams with the naked eye, when they are termed xylite". Higher rank coals have few or no roots visible. Peats, lignites, and sub-bituminous coals become higher ranks of coal (refer to the example I gave of the Matanuska coalfield in Alaska, showing a gradation of rank from sub-bituminous to anthracite in the same coalfield). Stach again: "Commonly, wood-rich peats with high lignin contents are deposited which, during coalification, are transformed into xylite-rich, soft brown coals and vitrain-rich bituminous coals with vitrites and exite poor clarites."

  [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.

  {KS replies} Yes. See above.

  [BP]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 replies} I maintain that partings are from a clastic influx into the coal swamp, due to overbank flooding or a marine transgression. Lack of trees can be because there were few or no trees growing in the swamp, or because the trees were flattened by the influx of water.

   

  I have shown you a parting with roots in the top of it, haven't I? I admit that this is probably the exception, and most partings don't have visible roots. If you are explaining roots below the main seam by waterlogged roots dropping vertically from the floating mat, how do you explain with your model the lack of roots in the top of partings? Why don't the partings exhibit the same dropping of waterlogged vertical roots from the mat?

  [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.

  {KS replies} In this thread, we are talking primarily about the Gates coals. You led this off on Nov. 28, 2003 by saying "It's quite obvious, Glenn, when you look at the details (where the devil is), that the J seam was transported." This discussion inevitably branches off to talk about other coals, which is OK, but it started with the Gates coal in the photos, and we should fully discuss that before moving on.

  [BP]I freely admit to not having all of the answers,

  {KS replies} In your Nov. 28 statement quoted above you sound very sure of the statement you make. Bill, no person has all the answers. The way to investigate these things is to gather data, think about it, then try to make conclusions - not the other way around.

  [BP] 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 replies} Bill, you still have not answered the question. You won't mind if I refer to the "floating mat speculation" from now on, will you? Your speculation does not fit the above observational data, and must be modified or rejected.

   

  The "coherent picture" you refer to is the insitu model. It fits the data well. Does it explain every single piece of data perfectly? No. It fits the data better than your speculation.

   

  If you wish to seriously challenge this model, you need to come up with a model that explains the data better. You have not done that.

   

  We can continue looking at more data about Gates coals and seeing how it is best explained, but a lack of an answer to my question leaves your speculation with a fatal flaw, in my opinion.
   
  [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?

  {KS replies} No, as I understand it, it's a one way street. Once the peat is oxidized, it cannot revert to vitrinite.

  Kevin
Received on Mon Jan 5 09:07:07 2004

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