Pet Wood in the Morrison Formation

At least 10 fossil log sites in Rainbow Draw have been documented so far, and geologic mapping indicates that the logs and wood all occur in the same stratigraphic interval within the Salt Wash Member, approximately 17 to 27 m above the base of the member. The unit containing the logs and wood is about 11 m thick and consists of very fine to fine-grained sandstone and siltstone with indistinct bedding and no discernible sedimentary fea-tures. The logs are siliceous, some have a coaly exterior, and they range in exposed length from 0.5 to 11 m and reach diameters up to 1.1 m. In the Miners Draw area, a single siliceous log is documented in the upper part of the Salt Wash Member within a silty sandstone unit that is 4 m thick; its exposed length is about 6 m. Although the correlation of the Miners Draw log-bearing interval to the interval in Rainbow Draw is uncertain, both units are lithologically similar and both occur in the upper part of the Salt Wash Member. The logs have been identified as araucariaceous conifers that pertain to the same taxon originally described as Araucarioxylon hoodii Tidwell et Medlyn 1993 from Mt. Ellen in the Henry Mountains of southern Utah. Concurrent systematic work will prompt a nomenclatural transfer of this species to the genus Agathoxylon.Based on the abundance of large fossil logs and wood in the same stratigraphic interval in Rainbow Draw, we hypothesize that the area was covered by stands of moderately large trees of araucariaceous conifers. The sedimen-tological evidence suggests that the trees were not transported far from their original site of growth before they were deposited in a low-energy floodplain environmen

I can attest that the green layer (and the adjacent purple layer) is a marker I look for when I'm treasure hunting. Very close to these layers is where I've found the vast majority of pet wood, coprolites and dino bone. I've read in scientific literature that the purple layer has a tremendous amount of plant material in it and from what I've seen I would say it's true. Today it just looks like colored badland dirt. It sure would have been interesting to have watched what happened to that area from a safe distance.

Also, that layer is shot full of old uranium mines.