Enjoy
Subject: Re: Janet Miller Remonstrates
Date: 2 Nov 1998 02:04:38 -0500
From: Chris Nedin <cnedin@ediacara.org>
Organization: Newsguy News Service [http://www.newsguy.com]
Newsgroups: talk.origins
In article <71feg8$e3a$1@nnrp1.dejanews.com>, janetmiller@my-dejanews.com
says...
>
> The purpose of this posting is to clarify an issue
>that has become so involved from willful obfuscation as
"Willful obfuscation"? Or do you mean that you were not previously aware
of the extensive amount of information on septarian concretions?
>to be unintelligible except to a diehard few; indeed,
>the last posting printed out to 8 pages! At issue here
>is a challenge to the Principle of Uniformity (and
>hence to the theory of evolution) offered by Richard
>Petersen and reiterated by me on my Web Page--
>specifically in the segment labelled "Petersen's
>Central Theorem at
> http:/www.webcom.com/jlmiller/page2.html
>Here that author proves a heretofore unsuspected earth-
>shaping phenomenon which is utterly at odds with the
>Principle of Uniformity--one that reduces much of
>modern geology to a nullity.
Actually no, it doesn't, since is utterly fails to explain the formation
of similar phenomena in the marine environment where there is no evidence of
asub aerial exposure or sub aerial deposition - a point I have brought up
several times now and which you have failed to respond to.
> The proof reduces to four simple steps involving
>properties of the loess and certain peculiar nodules
>widely occurring within this silty deposit. In order
>to rebut the theorem it would be necessary to show
>either that one or more of those steps is faulty or
>that the observed facts can be explained in some way
>more agreeable to the Uniformity Principle. The
>outspoken defenders of Uniformity have attempted the
>latter course.
Not accurate, since I have pointed out several problems with Petersens
method - none of which you have replied to. Once again they are:
- Septarian concretions are also found commonly in fully marine sediments with
no evidence of sub aerial exposure and no evidence of sub aerial deposition.
- Septarian concretions often show second and third generation cracking,
necessitating 2 or 3 separate events of aerial transport.
- If the central area of the concretion was not solid, but the outer crust was,
a fall of only a few metres would smash the concretion, rendering it
unrecognisable, and certainly not round or oval.
- Concretions (especially septarian concretions) normally solidify from the
external surface inwards, so there would not necessarily be a nucleus at the
centre of the concretions - the absence of which, you suggest above, is a
problem.
> In essence, their rebuttal proceeds as follows:
>Firstly, they plead that the nodules are more properly
>identified as "septarian concretions" and, quoting from
>a post by Chris Nedin, and subscribed to by Andrew
>MacRae and others, the concretions are formed by
>"differential dessication or internal/external pore
>pressure differential during burial. ... Basically the
>outer layers of the concretion solidify, producing an
>outer, solid crust. The inner parts of the concretion
>remain soft and slowly dry out as pore fluids exit
>through small holes in, or thinner parts of, the crust.
>Since drying out reduces volume, but the volume is
>'fixed' by the solid crust, the concretion connot
>shrink in size and so the internal mass fractures,
>allowing gaps to open up to accommodate the reduced
>volume of material...."
> And that is the end of the explanation offered by
>those august authorities. But it should be obvious that
>they have omitted one key element. Namely, they have
>given no explanation for those muddy globs in the silt,
>the drying of which gave rise to the concretions. Not a
>word. Apart from that crucial omission their
>explanation is similar (but not identical) to
>Petersen's. The difference is that the muddy globules
>must have had a crust of sorts even before they were in
>place within the silt--otherwise the surface would not
>have been so smoothly defined.
> I make bold to anticipate that the worthy doctors
>cannot contrive a mechanism whereby even one such muddy
>globule could form within that body of silt--by a mode
>consistent with the Principle of Uniformity. How much
>more difficult it would be, then, to account for the
>multiplied billions of them that must occur within the
>formation as a whole on three continents.
Ahhh, now I see the problem.
The formation of concretions does not rely on the presence of "globules" of
water. The concretions form in the sediment/soil which is fully saturated. In
the marine environment this is easily achieved, since the sediment is always
fully saturated. However, in soils the saturation comes from the local
groundwater or water table.
In marine sediments, the formation of concretions is governed by fluctuating
Eh-pH conditions. As pore fluids become more acidic, the fluid can hold more
dissolved carbonate (just like hot water can hold more dissolved sugar than cold
water). As the Eh-pH boundary falls, the pore fluids become less acidic and
unstable with regard to dissolved carbonate, forcing the precipitation of solid
carbonate between the grains of the sediment (just as a cooling glass of sugar
saturated water will precipitate out sugar). Often pre-existing carbonate in
the form of shells acts as a nucleating site to prompt the precipitation
process.
In soils it is a little different, since it is the water table that fluctuates
up and down, rather than the Eh-pH levels. When the water table is high, humic
acids from the break-down of organic matter cause a fall in pH to more acidic
levels. The fluids then carry more dissolved carbonate in solution. As the
acids are diluted, either by being removed by growing plants or diluted by more
water flowing through, the pH rises and the fluids become supersaturated with
regard to carbonate, precipitating carbonate around nucleating sites such as
carbonate nodules or carbonate shells. If the water table falls, the outer
layers of these concretions dry out to form an almost impermeable shell around
the, still wet, interior - which may be water-saturated sediment, or a
carbonate-sediment gel. If the water table remains low, then the concretion
begins to dry out inside and crack - or with subsequent burial, to as shallow as
10 metres, differential pore pressures causes cracking.
Groundwater flow through loess is well documented, e.g
Zilberbrand, M. (1995) The effect of carbonates and gypsum precipitation in the
root zone on the chemical composition of groundwater. Journal of Hydrology. 171;
1-2, Pages 5-22. 1995.
Partial Abstract: The boreholes were drilled to groundwater levels situated in
loess loams at depths of 10-24m.
Van Iten, Heyo.; Simpkins, W.W. & Aravena, R. (1996) Dissolved organic carbon in
the till and loess units of Iowa; implications for nitrate contamination of
groundwater. Abstracts with Programs - Geological Society of America. 28; 6,
Pages 68.
Zhou Zongjun (1994) Application of pipe wells to dewatering engineering in loess
district. Ministry of Mechanical and Electric Industry, Institute of Surveying,
Xi'an, Gongcheng Kancha = Geotechnical Investigation. 1994; 1, Pages 41-43.
Abstract: Methods and applications of groundwater lowering and features of loess
in Weihe River basin are presented in this paper. The use of pile wells for
groundwater lowering in loess district is emphasized. In the engineering
practice, the method of well point precipitation is selected according to the
size of filtration coefficient of foundation soil.
In short, there are several explanations as to the formation of septarian
concretions, all in accordance with the "theory of uniformity" (if I understand
the term).
Now, could you please address the problems I have pointed out with Petersen's
method. Then we can discuss the problems with Petersen's method highlighted by
oxygen, carbon and sulphur isotopic studies of concretions.
Chris
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