Re: Canadian Coal - unanswered questions

Hello again, Kevin,

Relative to a portion of our unfinished discussions - I was recently
logging soil cores in Memphis, Tennessee. We were using "Rotosonic"
drills to take continuous 4-inch cores as deep as 240 feet. The section
consists of about 20 feet of loess (brown silt with minor clay), several
feet of sandy clay to clayey sand, maybe 60 feet of a series of fining
upward units of sand and gravel, a gray clay from 0 to ~25 feet thick,
and fine sand to a depth of about 300 feet, where the Memphis Aquifer is
penetrated.

I thought of you when we had drilled through some sandy clay and I
noticed that it contains minor amounts of shell fragments and subangular
to subrounded chert. The largest fragment I have found in the core is a
piece of subangular chert which has a flat bottom and is 2.0 cm long x
1.0 cm wide x 0.8 cm high (rounded on top). I have not yet done a sieve
analysis, but I suspect there is a smooth gradation of grain sizes from
this subangular chert down to clay. I'll send you some photos offline.

On Wed, 17 Mar 2004 22:24:43 -0700 "Kevin Sharman" <ksharman@pris.bc.ca>
writes:

> 12. Stokes Law
>
> You commented that unknown and unconsidered variables may alter and/or
> invalidate Stokes Law. No comment when I asked what the unconsidered
> variables would be, and no explanation of why the observed data in
seams is
> inconsistent with Stokes Law settling.

I filled a glass cylinder with 42 cm of water and dropped the chert
fragment into the water; it took and average of 1.16 seconds to settle 42
cm. Six smaller particles took an average of 1.66 seconds to settle 41.5
cm in water. At the settling velocity of 42 cm per 1.16 seconds, that
particle will settle 3.13 x 10^6 cm/day. We know from Stokes' Law that
clay particles (radius of 0.0001 cm) settle at 3.67 x 10^-4 cm/sec or
3.17 x 10^1 cm/day. This is a difference of 5 orders of magnitude in
settling velocity between the clay particles and chert, yet these clay
particles are found homogeneously mixed with a gradation of courses
particles.

How do you propose to get this mix of grain sizes in a water-borne
deposit?

Bill

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Received on Thu Jun 17 00:54:06 2004