Re: Canadian Coal - depositional setting

From: Bill Payne <bpayne15@juno.com>
Date: Wed Jan 28 2004 - 00:51:00 EST

On Mon, 26 Jan 2004 23:02:23 -0700 "Kevin Sharman" <ksharman@pris.bc.ca>
writes:

> I don't think even a rootbound mat could stay together for more than
about 5
> minutes after being ripped off the earth by a "massive wave which
overtopped
> the continents" and bobbing around while the entire earth is being
> rearranged. I think you're coming around, Bill! :-)

Well, I am beginning to feel a little dizzy.

> Sorry, let me clarify. What I'm saying is this:
> 1. water table rises (clean groundwater), drowning peat and
> stopping growth.
> 2. trees topple over because their roots rot out
> 3. decomposition proceeds at the submerged peat surface with
> limited oxygen, breaking down and gelifying peat
> 4. peat surface is now smooth. Clastic influx creates parting.
> 5. if conditions are right, the peat swamp re-establishes
> itself on top of the parting.

> You don't need to keep turbid water out of the swamp. As I mentioned
> before, a clastic influx into the swamp while it's still growing won't
make
> a parting. Bioturbation by roots will incorporate the mineral matter
into
> the coal.

Two things:
1) You've got the clastic influx down at step 4, after the peat surface
is smooth. What happens if a clastic influx hits the swamp after step 1
and before step 2? Tree trunks should be preserved in the parting. The
roots are dead so there will be no bioturbation from roots. I would
expect bioturbation by critters unless this is an oxygen-deficient
environment. On 1/25/04 you said: "At the top of the peat when it is
submerged, there is oxygen. Peatification proceeds until the oxygen is
used up, then anaerobic decomposition kicks in (deeper in the peat
profile)." So are these lake bottoms oxygen deficient, and if so, why?
Are modern drowned swamps oxygen deficient?

2) In step 5, if the peat swamp doesn't reestablish, then the parting
isn't a parting, it becomes part of the roof (rock above the coal seam).
If the swamp does reestablish, I assume we are past the shrub phase and
trees will resume growing. And bioturbation (I think I'm re-re-repeating
myself, but who am I to mention such a thing :-)) from the roots will
destroy the parting. There, at last - CHECK! :-)

> Picture the whole package prograding as a unit. At a given time, the
> shoreface sand is prograding, fed by the distributary channels passing
> through the swamp. The swamp "follows" the shoreface as it progrades.
> Meanwhile, at the mountain front, material is being eroded, some of
which
> covers the swamp to form the interseam rocks.

Kevin, you knew I wouldn't blow by that. You say the sand is "fed by the
distributary channels passing through the swamp." On 1/25/04 you said:
"There would be a series a few of distributaries feeding sediment, which
was redistributed long distances by the longshore drift (to the next
distributary).

I asked: "Do you have any photos of a river channel cutting the coal?

You responded: "In the intensively explored and mined area (20 km X 10
km), there are no river channels cutting the basal coal. There is an
area I can think of where the basal coal thins to ~1 m, but I can't say
if this is because it's cut out by a channel. Outside of this, drillhole
control is more sparse."

You admit that "there are no river channels cutting the basal coal" in
the area most likely to see them - "the intensively explored and mined
area." You mention an area of thin coal, but you don't know if it's a
channel cut. Then you say "Outside of this, drillhole control is more
sparse", which is another way of saying you have no observational
evidence of channels in the areas where data is limited, and you have no
observational evidence of channels in the areas where data is intensive.
Kevin, you and Carmichael believe in distributaries because you
intuitively know you must have them to prograde the shoreline, but you
have never seen with your eyes what you say must be there for your model
to work. I think this is called blind faith. In fact, what you are
doing is more blatant - you are propounding channels feeding
distributaries when the observations say there are none.

You also said: "See the Carmichael abstract. 'The channels are mainly
braided river types with anastomosing or straight (non-braided) and
meandering river channels also present." See also the block diagram of
the Gates which I posted a link to. The core photos are most
instructive.'" Excuse me, but WHAT channels? I sorry, I didn't mean to
yell. But Carmichael is referring to channels that aren't there. From
what I understand, there may be channels in the interseam sediments (big
deal), but there are none in the swamp deposits, i.e., there are no
intraseam channels. And without intraseam channels to transport sand
across the swamp, you cannot prograde the shoreline while depositing
peat.

Maybe I completely misunderstand the model, but hopefully you can see
where I am getting hung up and help me past these points. Ummm, I feel
better; not so dizzy anymore.

> A whole series of environments, detailed in Carmichael's abstract. You
have read it, haven't you?

I guess you could do anything with "a whole series of environments."
I'll get back to that later. We also need to talk about coal seams
"draping" topography.

Later,

Bill

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Received on Wed Jan 28 01:07:46 2004

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