Floating mats and coal - settling rates

From: Kevin Sharman <ksharman@pris.bc.ca>
Date: Fri Feb 20 2004 - 16:47:05 EST

Hi Bill,

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. The equation is:

V = (2gr^2)(d1-d2)/9mu

where

V = velocity of settling

g = acceleration due to gravity

d1 = density of particle

d2 = density of medium

mu = viscosity of medium

An online Stokes Law calculator can be found at
http://www.filtration-and-separation.com/settling/settling.htm

The acceleration due to gravity is assumed to be constant (if you want to
vary this during the Flood you need to show how and why), and the viscosity
of water decreases with higher temperature, but there is an upper limit to
this in your scenario, since you don't want to kill the fish that survived
the Flood. The two variables of interest are the radius of the particle
and the density difference between the particle and the medium. Particle
size: The larger the particle, the faster it will settle. When we look at
the particle size of materials that make up coal, it is quite variable,
ranging from meter scale logs and stumps to micrinite, which is defined as
inertinite less than 2 microns. As I discussed in an earlier post,
inertinite could not have formed underwater from vegetation. Also spores
and pollen are very small (from a few microns to a millimeter).Density
difference: One of the terms of the equation is the density difference
between the medium and the particle. Sediment is composed mainly of quartz
and/or clay minerals, with a density of 2.5 to 2.65. Seawater is 1.025.
The difference in density will be 2.65 - 1.025 = 1.625. Waterlogged wood
will have a density near to that of water; so the density difference between
it and water will be small. Coal macerals range from inertinite with a
density ~1.5 to the lighter macerals of vitrinite and liptinite, so again
the density difference between them and water is small (1.5 - 1.025= 0.475).
Sporinite (a variety of liptinite derived from spores) has a density of 1.15
to 1.25.From the equation, particles of a size at the lower boundary of silt
(4 microns) composed of quartz have a settling velocity of 1.4 X10^ -5
meters/sec, or 1.2 meters/day. If these particles are inertinite with a
density of 1.5, the density difference is only 0.475, and the settling
velocity is 4.1 X 10^-6 m/sec, or 0.35 m/day. To pile up the thickness of
vegetation that you need to make a seam, you need deep water. An 8 meter
thick seam needs a pile of vegetation 80 meters thick, assuming 10:1
compaction, so the minimum water depth is 80 meters. The inertinite
particle would take 228 days to settle through an 80 meter water column.
Spores would take even longer to settle due to their even lower density.
Remember that the Stokes' Law settling applies to still water, a condition
that is highly unlikely in a global flood. Any currents will result in
slower settling times. 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. 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.

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.

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.

So, once again, the floating mat idea fails the test.

Kevin
Received on Fri Feb 20 16:49:20 2004

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