Re: marine or eolian dunes?

Arthur V. Chadwick (
Mon, 02 Feb 1998 10:09:51 -0800

At 09:47 PM 1/30/98 -0600, Glenn wrote:

>>I don't see anything in these paragraphs that can be cited as a"major
>>sedimentological difference" unless by this you mean "smallest levels" or
>>"cannot be distinguished by their structural characteristics" or "generally
>>have" :-), but hyperbole aside (since I never am guilty of that myself),
>>these subtle bedforms are extremely difficult to see, even in the modern
>>environments, and I haven't seen them used to discriminate
>>paleoenvironments, probably because they are so subtle and difficult to
>The importance of that work is precisely that the smallest features of
>marine dunes differ from eolian dunes. This allows it to be used on oil
>well cores. It is a predictive difference which is observable and that also
>is important.

>I can understand why organic deposits like dung would be oxidized into
>oblivion in an extremely arid desert. I have difficulty with the idea that
>all organics would be destroyed in a subaqueous environment

Maybe you can also explain why these animals were living on a barren
desert. What did they eat? Anyway, Brand has demonstrated convincingly
that the trackways were made subaqueously, so any further discussion on
this point is moot. There is no semblance whatsoever between tracks made
on dry sand and those made in the Coconino. I think we can safely move on.

>I am not just now concording with you on this point. I agree that glauconite
>is marine. But it's lack in the Coconino and Navajo (as far as I have been
>able to find) should also be significant!

Not at all. Nobody, myself included, thinks the Coconino or Navajo were
deep water deposits. It would be exceedingly anomalous if glauconite were
found in either of them.

>Yes, and I will admit that I don't have a good one. So, what is your

Well, for starters, that they don't represent 260 million years of
depositional history. We can go from there....