Re: Roots in coal?

Hey Kevin,

On Mon, 22 Dec 2003 10:24:37 -0700 "Kevin and Birgit Sharman"
<ksharman@pris.bc.ca> writes:

> It is generally accepted that coals with the original peat or roof
> strata formed in marine influenced environments have a higher sulphide
> sulphur content than those with fresh water influence (Holuszko et al,
1993,
> Stach et al, 1982). The mechanism involved is bacterial reduction of
> sulphate (supplied by seawater) to sulphide.

> "Low ash and low sulphur coals were deposited as fresh water peats
> which were underlain and overlain by fresh-water clastic sediments in
> which limestones were absent." (Stach et al, 1982, Cecil et al, 1979a).

> The Gates Fm. coals are low in sulphide sulphur with the exception
> of D seam, the highest mineable seam. This is overlain by a
> conglomerate interpreted to be of marine estuary channel origin
(Carmichael,
> 1983), based on sedimentary features noted above, Macaronichnus
segregatus
> burrows, and its position below a marine lag facies.

> Using the above as criteria, the low sulphur coals of the Gates Fm.
> could not have been deposited in a marine floating mat model. A fresh
> water floating mat model would have to account for the lateral extent
of
> these coals (230 km X 90 km = 20,700 km2), deposition of the
interbedded
> sediments (65 m to 90 meters thick), and the multiple seams (8 seams,
0.5
> meters to 10 meters thick). Proposing a zone of fresh water in contact
with
> marine water leaves one with explaining why this would not be mixed.
Even
> brackish water peats have high sulphur content.
>
> Carmichael, S. M. M. (1983): Sedimentology of the Lower Cretaceous
> Gates and Moosebar Formations, Northeast Coalfields, British Columbia.

> Unpublished Ph. D thesis, Department of Geological Sciences, University
of
> British Columbia, 1983.
>
> Holuszko, M., Matheson, A., and Grieve, D. (1993): Pyrite
> Occurrences in Telkwa and Quinsam Coal Seams. Ministry of Energy,
Mines, and
> Petroleum Res., Geological Fieldwork 1992, Paper 1993-1, p. 527-536

> Partings in these coals range from small 1 cm bands within the coal
> to layers 1 to 2 meters thick. Parting composition can be mudstone,
> carbonaceous mudstone, and/or coaly mudstone, reflecting varying
> amounts of plant material in the original sediment. Contacts with the
> underlying and overlying coal range from sharp to gradational;
generally they are
> reasonably sharp. In two dimensions, the contacts are flat, but
> when the contact is exposed in 3D, undulations can be seen (up to 0.5
meters
> of relief).

> I have never observed tree trunks or stems extending from a seam,
> through a parting, into overlying coal (It has only been in the last
year that
> I have specifically hunted for details in the field relevant to the
origin
> of these coals; in my 16 years as a geologist at the operating mine, my

> priority was usually more "practical" matters). Roots are sometimes
observed in
> the top of the parting in these coals, evidently originating from the
coal
> above (Glenn has one of my photos on his coal page showing this, the
one
> with the label "shale with roots" in the lower right corner).

> I agree that one would expect at least some trees to be sticking
> through the parting if it were deposited by an influx of water and
sediment into
> the swamp (unless the influx of water knocks down the trees). I also
> agree that it is surprising that the lower contacts of the partings can
be so
> sharp and planar if the mud is draped over an irregular surface like
the top
> of a peat swamp.
>
> I submit that sharp planar contacts of the bottom of the parting are
> a problem for the shedding mat model as well. The pile of shed veg
> material would have relief on the top of it, especially if it has
larger
> trees and stumps in it. Then, when sediment is laid on top of it, the
layer
> should conform to the relief. But, as we can see, partings with
relatively
> planar bottom contacts occur. In answer to this, I would say that
> compaction of the veg material flattens out the top surface of it (this
applies to
> the floating mat model as well as the in-situ model).

> So, partings are another inconclusive feature in the coals with
> respect to our debate. If all partings had sharp contacts, no roots,
and no
> trees sticking up through them, it would be hard to explain with an in

> situ model. But some have these features, and some don't.

> It is the nature of geology that information is often incomplete,
> contradictory, and downright confusing. What we must do is sort
> through it, consider the range of possibilities, and pick the
possibility that
> fits the evidence best.

> I found a reference to coprolites in a German brown coal in Stach
> (p. 281-282). I haven't found any info on coprolites in Cretaceous
> coal.

Fecal pellets or coprolites in brown coal (lignite?) would be consistent
with what I have said about lignite being from post-flood, in situ peat
deposits.

> While looking for this, I found a reference to forams in marine peats:

> Cohen and Spackman (1977) quoted in (you guessed it!) Stach "(in
Florida
> peats) foraminifers were present in all marine and brackish peats". So
in
> your floating mat model, we would expect forams in the coal, since you
> are saying some were deposited in a marine environment. Are there
forams in
> any coals that you know of?

________________________________________________________________
The best thing to hit the internet in years - Juno SpeedBand!
Surf the web up to FIVE TIMES FASTER!
Only $14.95/ month - visit www.juno.com to sign up today!
Received on Thu Dec 25 23:11:46 2003