Anyway, Bill wrote:
> You "contend that he Coconino is terrestrial, not submarine..."
I contend that the consensus of most geologists who have studied
the Coconino Sandstone is that it is a subaerial deposit. Pick up any
geology text which mentions the Coconino and it's described as a
terrestrial sand dune deposit. I have not personally studied the
Coconino in any detail (other than seeing it in the field) therefore
most of my knowledge of it is secondhand from the primary geologic
literature.
> Glen Vishner, Prof. of Geology at Univ of Tulsa in OK, has:
>
> A. "noted that large storms, or amplified tides, produce submarine sand
> dunes called 'sand waves.'...
I wasn't able to find Visher's book but published descriptions of sand
waves in other texts seem to clearly show that they are NOT what is seen
in the Coconino. Why? Because as you say below, "the average slope of
Coconino Sandstone cross beds is about 25 degrees from the horizontal" and
sand waves have much shallower slopes. As Allen, 1982 (reference B below
so Austin should have known about this comment) writes:
"We cannot emphasize too strongly that sand waves possess low to mild
slopes ... it is clear that the sides of the waves rarely dip more steeply
than 10 degress overall and can slope as little as 1 degree ..."
Allen, John R.L. 1982. Sedimentary Structures: Their Character and
Physical Basis. Volume I. Developments in Sedimentology 30A. Elsevier,
Amsterdam.
So my answer to your comment is two fold. Yes, Virginia, there are such
things as submarine sand dunes but they have a totally different character
than the cross bedding we see in the Coconino which is more consistent with
desert dunes. Secondly, one cannot consider things in isolation since there
is abundant additional evidence to consider the Coconino to be a terrestrial
deposit (tetrapod trackways, raindrop impressions, etc.).
> B. Furthermore,...the average slope of the Coconino Sandstone cross beds
> is about 25 degrees from the horizontal, less than the average angle of
> slope of sand beds on the dwon-wind side of most modern-desert sand
> dunes. Those sand beds usually slope at an angle of more than 25
> degrees, with some beds inclined as much as 30 to 34 degrees - the angle
> of 'rest' of dry sand... modern oceanic sand waves do not have
> 'avalanche' faces of sand as commonly as desert dunes do, and,
> therefore, have lower average dips of cross beds.
I refer you to the following text:
Collinson, J.D. & Thompson, D.B. 1989. Sedimentary Structures (2nd
edition). Unwin Hyman, London.
They state that, for aeolian dune cross-beds, that while the large-scale
dunes do have slip faces of 33 to 42 degrees, trenching of modern dunes has
indicated that there are also smaller-scale bedding structures inside the
larger dunes with foresets dipping at 18 to 34 degrees (pages 95-97). This
is consistent with what we see in the Coconino.
Other texts state:
"The most characteristic feature of eolian dunes is their enormous
cross-beds... Individual cross-bed sets can reach 30-35 m in thickness,
with foresets that dip 20-35 degrees... Detailed studies of the faces of
eolian dunes ... shows that the ripples move laterally across the face of
the dune. This suggests that much of the cross-bed is formed not by sand
avalanching down the face of the dune but by sand blown horizontally
across its lee face."
Prothero, D.R. & Schwab, F. 1996. Sedimentary Geology: An Introduction to
Sedimentary Rocks and Stratigraphy. W.H. Freeman, NY, pg. 161.
Guess what, there are wind ripples on the lee faces of the Coconino cross-
beds. A photo of this (along with Coconino raindrop impressions) may be seen
on page 194 of Grand Canyon Geology by Beus and Morales (complete reference
given below). Therefore, an average dip of 25 degrees is indeed consistent
with them being desert dunes.
Also note that on this same page Prothero and Schwab have a wonderful set
of photographs. One shows cross-bedding in a section of a modern dune from
Great Sand Dunes National Monument in Colorado and the other photo shows
large-scale cross-beds in the Jurassic Navajo sandstone. They're virtually
identical.
The paper below has a very detailed discussion of all of the complex
cross bedding seen in the Coconino and how they're interpreted:
Middleton, L.T., Elliott, D.K., & Morales, M. 1990. Coconino sandstone.
In: Beus, S.S. & Morales, M. Grand Canyon Geology. Oxford University
Press, pp. 192-193.
Austin appears to me to be TWISTING the evidence. He selectively reported
only those facts which supported his idea (Coconino 25 degrees, dune slip
faces > 30 degrees, sands waves less than this) and ignores the complete
picture (yes, dune avalanch slip faces are > 30 degrees but dune foresets
can easily be as shallow as 20 degrees as seen in modern dunes and sand waves
aren't just less steep, they're significantly less steep at 1-10 degrees).
This type of selective winnowing of the evidence to support your preconceived
idea is NOT acceptable in science as you well know.
> C. Within this sandstone is a feature known as 'parting lineation,'
> which is commonly formed on sand surfaces during brief erosional bursts
> beneath fast-flowing water. Parting lineation is not known from any
> desert sand dunes.
The references you gave for these claims are a bit messed up. I'm assuming
that Visher's book is the reference for this claim, that the two papers on
the Navajo Sandstone and Altahama Estuary are references for claim D below,
and the Kuenen and Perdok paper on abrasion (labeled D below) really refers
to claim E.
Anyway, what you're calling parting lineations (which are often used for
paleocurrent analysis) seem to be interpreted in the following reference as
avalanching of loose sand down slip faces (pp. 195-196):
Middleton, L.T., Elliott, D.K., & Morales, M. 1990. Coconino sandstone.
In: Beus, S.S. & Morales, M. Grand Canyon Geology. Oxford University
Press, pp. 192-193.
Can you provide me with a better reference, perhaps with a photo, of these
so-called parting lineations?
> D. Different grain sizes of sand within any sandstone are a reflection
> of the process that deposited the sand. Coconino Sandstone does *not*
> compare as favorably to dune sands from modern deserts.
The references Austin gives for this claim are interesting. The first
is to a paper a study of the sediment size distributions in the Altamaha
Estuary and the second is to a study of sediment size distributions in the
Navajo Sandstone (see references below). This puzzles me because we're
discussing the COCONINO and the reference you give me discusses a possible
submarine origin for the NAVAJO. These are two entirely different units
(one Permian and the other Jurassic in age).
Nevertheless, maybe Austin believes that what applies to the Navajo also
applies to the Coconino since the Navajo is also interpreted to be a
terrestrial dune deposit and the paper by Freeman and Visher claims it looks
more like an estuary deposit. Perhaps the same can be said for the Coconino?
Once again, however, Austin only gives PART of the picture. Looking ahead
two volumes in the Journal of Sedimentary Petrology reveals that there were
four(!) discussions written in reply to Freeman and Visher's paper. Those
regularly reading geologic journals will realize that getting four
discussions reveals a very controversial paper. Perhaps Austin should have
also have referenced these discussions and reply? Would that not have been
the honest thing to do? They were all entitled "Stratigraphic Analysis of
the Navajo Sandstone: A Discussion" and appeared in the Journal of
Sedimentary Petrology, volume 47. Let me list the authors:
Picard, M. Dane (pp. 475-483)
Folk, R.L. (pp. 483-484)
Steidtmann, James R. (pp. 484-489)
Ruzyla, K. (pp. 489-491)
They all take Freeman and Visher to task. Let's look at some of their
comments about Freeman and Visher's work:
"Much of their conjecture is based on the rejection of criteria
advanced by others for interpreting the Navajo Sandstone as dominantly
an eolian deposit. Little new evidence is advanced by Freeman and
Visher in support of their ideas" (Picard, pg. 481)
"My comment concerns only the grain size data which the authors
(Freeman and Visher, 1975) claim offers no evidence for an aeolian
origin. On the contrary, their published results do, quite clearly,
support an aeolian origin for the Navajo sands." (Folk, pg. 483)
[Folk is a world-recognized authority on sandstones]
"...I have found that: 1. The data they have presented are equivocal;
2. they fail to recognize probable weaknesses in their methods and to
give alternative explanations of their observations; 3. they ignore
pertinent findings from other studies, and 4. They do not critically
examine certain evidence which appears to support their conclusion and
casually discredit equally valid and overwhelming evidence to the
contrary." (Steidtmann, pp. 484-485)
"I do not doubt that parts of the Navajo are indeed marine, but to
say that some of it is marine and therefore all of it is marine is
not logical stratigraphy. (Ruzyla, pg. 491)
By the way, Ruzyla's discussion also mentions how Freeman and Visher
accept an eolian origin for the Lukachukai Sandstone Member of the Wingate
Formation (pg. 491). So, even though Freeman and Visher might have argued
for a marine origin for the Navajo, they did accept that eolian dune deposits
are found in the Colorado Plateau making them no allies of global flood
proponents.
Anyway, the point of all this is that Austin evidently referenced this
paper by Freeman and Visher as evidence for a submarine origin for the
Coconino. What's the problem? It discusses the Navajo sandstone. That's
a different issue. Not only that, he referenced a paper without including
any indication that there were many severe criticisms of that paper published
in the same journal! One wonders what Freeman and Visher would say today, 20
years later, but they're no longer at the University of Tulsa or I would have
sent them some e-mail and asked.
> E. Pitting and frosting of sand grains, claimed by some to prove wind
> deposition, has also been investigated further. It now has been found
> that not only is the pitting *not* diagnostic of the last process to
> have deposited the sand grains (pitting can...form first by wind
> impacts, followed by redeposition by water), but pitting and frosting of
> sand grains can form outside a desert environment. For example,
> geologists have described how pitting on the surface of sand grains can
> form by chemical processes during the cementation of sand."
Yes, true, there are several possible mechanisms for frosting quartz
sand grains and it doesn't PROVE wind deposition. But it is CONSISTENT
with wind deposition (in other words, if these grains weren't frosted,
then we should have questioned their eolian origin). By the way, one of
the important chemical processes cited by Kuenen and Perdok (reference D
below) is the action of dew in desert environments by alternate solution
and deposition (pg. 648). So, just saying it doesn't have to be wind
forming the frosting and pitting doesn't mean it still did not form in a
desert environment.
"These textural and mineralogical characteristics are compatible
with an eolian environment in which sediment transport involves
numerous grain-to-grain collisions. These collisions result in the
mechanical destruction of less stable grains and in winnowing by the
wind. As McKee (1979) correctly pointed out, however, these
characteristics do not substantiate conclusively a wind-blown
origin."
Middleton, L.T., Elliott, D.K., & Morales, M. 1990. Coconino sandstone.
In: Beus, S.S. & Morales, M. Grand Canyon Geology. Oxford University
Press, pp. 192-193.
Bottom line, no geologist would be foolish enough to rely solely on
frosting of quartz sand to infer a desert dune environment (although it
is a good piece of evidence). Many other different factors have to be
considered and, for the Coconino, we have many pieces of evidence all
supporting an eolian dune environment.
> (Quoted from _Grand Canyon, Monument to Catastrophe_, Steven A. Austin,
> Editor, 1994, p 32-33. Refs cited by Austin:
>
> A. Glen S. Visher, Exploration Stratigraphy (Tulsa, OK, Penn Well
> Publishing Co., 2nd ed., 1990), pp 211-213
>
> B. John R. L. Allen, Sedimentary Structures: Their Character and
> Physical Basis (NY, Elsevier Science Publishers, 2nd ed., 1984),
> pp259-266
>
> C. Visher, op. cit, p 213. W. E. Freeman and G. S. Visher,
> "Stratigraphic Analysis of the Navajo Snadstone," Journal of Sedimentary
> Petrology 45 (1975): 651-668. G. S. Visher and J. D. Howard, "Dymanic
> Relationship Between Hydraulics and Sedimentation in the Altamaha
> Estuary," Journal of Sedimentary Petrology 44 (1974): 502-521.
>
> D. P. H. Kuenen and W. G. Perdok, "Experimental Abrasion - Frosting and
> Defrosting of Quartz Grains," Journal of Geology 70 (1962): 648-658.
These references are good starting points, but there are many, many other
more recent references which Austin should have cited but apparently didn't
because they do not support his thesis.
> Now, Steve, Austin has listed 5 observations deduced by MN as pointing
> to submarine deposition of the Coconino Sandstone. Yet you still
> contend that the Coconino was deposited subaerially. On what MN basis?
Austin's references are all lacking in that (1) some of them don't even
support his thesis when you read them carefully and (2) he is only presenting
a part of the evidence and ignoring the rest (which is, unfortunately,
typical of young-earth creationists). It's not I that contend the Coconino
was deposited subaerially, it's all of the geologists who've spent years
studying it in great detail using methodologically-natural science.
It's only those people who want to invoke a miraculous global flood as the
cause of all sedimentary strata who insist that the Coconino must be marine
since their model crumbles like a cheap house of cards if it isn't.
- Steve.
-- Steven H. Schimmrich Physical Sciences Department schimmri@kutztown.edu (office) Kutztown University schimmrich@earthlink.net (home) 217 Grim Science Building 610-683-4437, 610-683-1352 (fax) Kutztown, Pennsylvania 19530 http://home.earthlink.net/~schimmrich/