Re: More and More Navajo sandstone plants

Arthur V. Chadwick (
Fri, 13 Feb 1998 10:18:19 -0800

At 09:08 PM 2/12/98 -0600, you wrote:
>For your consideration, Art,
>"Silicified wood has been reported previously from the Navajo Sandstone
>(Triassic-Jurassic) near Moab, Utah; additional information is now at hand.
>At least five individual trees represented by stumps standing in place of
>growth, [...] a
>limestone lens ranging up to 72 cm thick lies about 3.2 m above the root

> "This and similar fossil 'forests' must be taken into account in
>reconstructing the paleoecology of the Navajo. it is possible the scattered
>ponds and small groves of trees provided food and perches for the pterosaurs
>known to have left trackways in nearby localities."

>"Silicified wood fragments as much as 20 cm. in diameter are widespread in
>outcrops of the Triassic-Juraswsic Navajo Sandstone near Moab, Utah. The
>is typically found in indistinctly crossbedded sandstone peripheral to thin,
>discontinuous carbonate beds. some trunks are in nearly vertical position
>suggesting in situ preservation. Smooth, fluted surfaces on some fragments
>indicate abrasion before burial.
> "Diverse tubular and cylindrical structures, typically in diameter are
>also abundant in the Navajo. They occur just below horizontal truncation
>planes which separate sets of crossbeds. Crossbedding is indistinct below
>truncation planes, and distinct and undisturbed above. Tubes are composed of
>an outer sheath of well-cemented sand surrounding a core of calcite spar;
>cylindrical features consist entirely of sand. These structures have many
>similarities with root casts in Holocene dunes at Arches National Park, near
>Moab, and have important implications concerning depositional environments of
>the Navajo Sandstone."

Interesting stuff. I predict a careful examination will demonstrate, as it
did in Yellowstone that the trunks are transported, that the limestone will
reveal fossils incompatible with sanddunes, and that the root casts are
truncated abruptly.