Re: Floating mats and coal - settling rates

Hi Kevin,

Man, am I ever getting behind. Twelve-hour work days plus family
responsibilities don't leave much time for my favorite hobby. At least
we're busy though, the alternative isn't very pleasant.

On Fri, 20 Feb 2004 14:47:05 -0700 "Kevin Sharman" <ksharman@pris.bc.ca>
writes:
 
> Settling of vegetation from a floating mat would take time. To examine
how
> much time it might take, let's look at Stokes' Law. This law governs
the
> settling velocity of particles in a fluid. [snip]

Two comments - one to the settling velocity, and one to the larger issue
of how we interpret data.

1) As I recently related, the acidified sampling vial had clear water
within 2 minutes from the turbid sample taken from a 2-inch diameter
monitoring well where the water had been standing still for several
hours. I assume that the water cleared due to the acid causing
flocculation of the suspended fines.

A lower concentration of acid will still cause flocculation, although at
a slower rate. "The inference of pH influences is based on modern
analyses in the topogenous mires of the southeastern United States, where
pH differences in water chemistry cause clay to flocculate adjacent to
the channel margin, apparently limiting extensive inundation into the
mire (Staub and Cohen, 1979)." (Greb, S.F., Elbe, C.F., Hower, J.C.,
Andrews, W.M., 2002. Multiple-bench architecture and interpretations of
original mire phases -- Examples from the Middle Pennsylvanian of the
Central Appalachian Basin, USA. International Journal of Coal Geology 49,
151.) The pH of water is one factor that can alter or invalidate Stokes'
Law, and there may be others.

2) Your post, to which I am now responding, was written after I had
described the accelerated settling rate of my acidified sample, and after
you received and I think worked your way through the Power Point
presentation I sent you - where the above quote appears. It seems that
either you miss the significance of the effect of low pH on Stokes' Law,
or I am overrating the importance of low pH. My point here is that there
are always factors which we may not have included in our scenarios of
past events, factors which have the potential to completely undo our
conclusions.

> Then there is the time lag for the wood to get
> waterlogged. The coastal logging industry in BC moves a lot of logs in
> booms. These log booms can sit around in the harbor for months without
> sinking.The net result is that there is no way that you have enough
time in
> a year long global flood to soak vegetation long enough to first
waterlog it
> and then have it settle out on the sea floor to make up the dozens to
> hundreds of seams in the geologic record in a given area.

This is good news. As fast as the vegetative debris (that washed into
our lake and formed a little floating mat by the shoreline) sank out of
sight (I assume it sank since I didn't notice it floating out from the
shore), I've been concerned that the mat might sink too fast. What
washed into the lake was dead to begin with though; live vegetation would
last longer.

As I have mentioned before, at some point the Flood would have ended, but
recession of the waters/emergence of the land may have occurred gradually
over a longer period of time. Deposition of peat may have begun after
the end of the Flood, but while much of the land was still flooded.

> Remember that you
> also need time to deposit the other sediments, such as the ~9000 meters
of
> other sediments that make up the Phanerozoic succession in the area of
Gates
> Fm. coals.

I'm working on the foundation (coal) now; I would like to leave the
superstructure till later, or to others. If I can reasonably show that
coal is from transported peat, then the under- and overlying strata will
have to be reinterpreted in light of the allochthonous nature of coal.

> Also, the order of settling of plants/peat would be the large dense
> particles first (large inertinite), as well as large waterlogged wood.
In
> the middle would be small particles with a high density difference
(small
> coalified macerals), then last would be small particles with a low
density
> difference (small pieces of waterlogged wood, spores) and pieces with a
> large surface area to mass ratio, such as leaves and sheets of lycopod
bark.
> This is not the order we see, either in a given seam or as an upward
trend
> in the world's coal.

There are too many unknown or unconsidered factors for you to draw this
order of settling.
 
> How do you explain discrete beds of sporinite (spore rich layers) in a
> floating mat scenario? These very small particles with a low density
> difference would take a very long time to settle. In the mainstream
view,
> these settle out slowly in a lake environment with an absence of
clastic
> input.

This line of reasoning is secondary to more direct data indicating the
allochthonous nature of coal, IMO.

Bill

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Received on Sat Feb 21 23:40:02 2004