Re: Navajo Sandstone food

Arthur V. Chadwick (
Sat, 07 Feb 1998 13:06:19 -0800

At 09:47 PM 2/5/98 -0600, Glenn wrote:

>Well, the first shipment didn't arrive until today. But I have an answer to
>Art's question about what the animals in the Navajo ate. They ate plants
>that grew in interdune areas.

Naturally, but is there any evidence that there were plants there, or is
this just an assumption based on the desire to find a food source for them,
and a plausible scenario. If there was a food source, it should have left
imprints of the plants in the sand, as is evident in lots of other
localities where plant impression fossils are common in sandstones, even
those which preserve none of the original organic material.

"... ONly root casts and burrows are locally abundant in
>some dry interdune deposits or on deflationary interdune surfaces
>(first-order bounding surface).

Root casts are defined here as burrow-like structures that could be roots,
rather than root-like structures that contain the remains of fossil roots,
I imagine. What is the data that suggest they are indeed remains of roots,
other than their shape, which we have already discussed under a different

Of the seven localities in the Navajo
>Sandstone now known to have produced body fossils of terrestrial
>vertebrates, three are associated directly with interdune deposits.

But did these "interdune" deposits have plant fossils in them???

A relatively diverse biota, especially one that includes large
>vertebrates, in deposits from wet interdunes implies either that these
>plants and animals were able to utilize locally mesic environments within
>active ergs, or that these interdune areas formed during periods of wetter
>climate and relative dune stabilization during erg development."

"Or that some other model that makes more sense and accords better with the
data is the correct explanation, like for example that they were deposited
in water far from where they lived and where their food supply lay."