On Sat, 06 Jan 2001 22:38:59 +1100 Jonathan Clarke
<jdac@alphalink.com.au> writes:
> Hi Bill
>
> Silvestru can't know as much about karst as he says he does if he makes
these
> statements.
Dear Jonathan,
Thank you so much for your response. I had thought I might receive
something like yours, and I appreciate it.
I did my graduate work at the University of Tennessee and mapped a quad
which included the Knox Dolomite at the base of the section, and a number
of other carbonates above the Knox. Although I wasn't looking for karst
at the contacts, it is my general recollection that the only karst I saw
was on the outcrops which had weathered for years. I do know that there
are plenty of carbonate formations here in Birmingham and north in
Alabama which display planar bedding and a planar contact with overlying
formations. In fact, I don't recall ever having seen any karst
weathering except at the ground surface or in caves.
On page 208 of _The Genesis Flood_ by Whitcomb and Morris, there is a
photo of Jeffersonville Limestone (lower Middle Devonian age) overlying
Louisville Limestone (Milddle Silurian age). The photo caption says:
Figure 23. A "Deceptive Conformity," or Paraconformity. This is a
typical example of an extremely common, yet quite paradoxical,
phenomenon, namely the perfectly conformable superposition of a younger
bed upon a much older bed, with many intervening geological ages entirely
missing. The Jeffersonville limestone, of lower Middle Devonian age, is
here resting quite normally upon the Loiuisville limestone, of Middle
Silurian age. The significant thing is that these formations are
separated by more than 3000 feet of strata in other parts of the
Appalachian trough, and therefore it must be assumed that many millions
of years elapsed between them, although they look as though they must
have been laid out in quick succession. This phenomenon has been
variously called a "disconformity," a "deceptive conformity," and, more
recently, by C. O. Dunbar and John Rodgers, a "paraconformity."
(Principles of Stratigraphy, New York, Wiley, 1957, p. 119).
Also, on page 210 of _The Genesis Flood_ is "Figure 24. Double
Paraconformity." The caption says: In this Tennessee quarry are exposed
two major paraconformities, above and below the Pegram limestone, which
is lower Middle Devonian. The Chattanooga shale above is upper Devonian
and the Lego limestone below is Middle Silurian. Again there is no
physical indication whatever of any substantial time lapse btween the
deposition of these various strata.
Do you have any explanation for the _lack_ of karst weathering in the
formations described above?
Bill
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