Re: marine or eolian dunes?

Glenn Morton (
Wed, 04 Feb 1998 20:48:08 -0600

At 03:21 PM 2/4/98 -0800, Arthur V. Chadwick wrote:
>At 08:50 PM 2/3/98 -0600, Glenn wrote:
>>I don't think the suggestion is that the tracks were made in dry sand. The
>>suggestion was that they were made in damp sand. I think most would agree
>>that you can't make good tracks in absolutely powder dry sand.
>The problem then is how do you preserve tracks in damp sand? If it rains
>again before they are covered, they are gone. If the sand dries enough to
>blow around, they will also dry out and be destroyed.

It seems to me that a global flood has worse problems in this regard. The
sediment is always soppy wet never allowing the tracks to harden. Any
jostling of the sediment via faulting (which must have been going on during
the flood) will liquify the sand (take water soaked sand place a steel
marble on it and pat the surface with your hand. The marble will sink. Any
structure in hte sand will also liquify). In soppy wet sand with water
flowing, the tracks are likely to become very indistinct very rapidly. How
long do foot prints on the bottom of beach sand in 2 feet of water last? If
tracks are made underwater, there ought to be thousands just offshore of
Padre Island.

How do you preserve the tracks? How do sand castles stand up. There is
enough evaporative residue from the water to maintain the coherency of the
sand castle.The residue acts as a glue.

Then there is the
>problem of how to get dunes wet without eroding them and leaving evidence
>of the rain.

As I have noted several times, layers with tracks are quite often associated
with raindrop impressions AND mud cracks in many places.

>>And I do not stand as alone as you might think.
>>"Glauconite is a mineral which is widely believed to form only in marine
>>environments and to be so unstable that it cannot survive re-working. It
>>is therefore held to be diagnostic of marine rocks. This criterion is not
>>infallible. Detrital glauconite occurs in fluviatile Neogene red beds in
>>the Dead Sea Valley. As a general rule however glauconite is a useful
>>indicator of marine environments and studies of the present day distribution
>>of glauconite suggest that it may be possible to narrow down the precise
>>conditions which limit its formation."~R. C. Selley, "Ancient Sedimentary
>>Environments" 2nd ed. 1978, p. 8
>Note the logic: "Glauconite is widely recognized as a deposit formed on
>the ocean floor (below 100 meters). However, we have these fluviatile
>neogene beds (based on sed structures, etc.) that have glauconite in them,
>so we will ignore the DATA from the modern environment and
>this case, the present must not be the key to the past". ????

First, the 100 meters didn't come from me and if it is true, what is your
source for the 100 meter limit?

And no, the present is NOT always the key to the past and I know of few
geologists that require everything in the fossil record to be explained by
things we have witnessed today. Banded iron formation, widespread dolomite
deposition, and other things have been difficult to understand because we
don't see these things occurring today.

>>Krauskopf, Introduction to Geochemistry, 1967 writes:
>>"Under mildly oxidizing conditions in shallow seas, ferric iron may go into
>>glauconite [approximately KMgFe(SiO3)3*3H2O], and near hot springs (perhaps
>>sometimes also as a result of ordinary weathering) into jarosite[...]." p.
>This statement is speaking of alterations to glauconite, not to its
>formation, as ferric iron is not a normal dominant component of glauconite.
> Glauconite is believed to form under reducing conditions when organic
>matter is available in the sediments (thus the Fe++).

Glauconite is glauconite regardless of the pathway.

>>None of these say anything about deep water. And Dot and Batten, 1988
>>Evolution of the Earth, p. 290 merely say that it requires slow deposition.
>>Some of the past epeiric seas where shallow and had slow deposition. And as
>>you know depositional speed is not restricted only to deep waters.
>Glauconite is not a product of slow deposition, but of anoxic alteration of
>sediments containing high concentrations of organic matter. The
>environment of formation is outer shelf to upper slope (sea floor) in water
>depths exceeding 100 down to at least 500 meters (it is dredged off the
>sea floor far from sources of sediment), where according to Weaver ("Clays
>Muds and Shales") it is forming today off the continental margins of east
>and west coasts of North America, along the southern areas of South
>America, northern Spain, southern Japan, southwestern Australia, eastern
>and southwestern Africa today. Deep is a relative term, but none of this
>is "shallow", in the sense that it is all below storm wave base (my
>personal distinction between shallow and deep).

Storm wave base is generally much shallower than 328 feet (100 m). You
must have experienced some whopper storms in your life.


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