The Supai Group

In Northern Arizona

(Uploaded 1/3/09)

The Supai Group is a label that was used in the past to describe everything from the Hermit Shale up to the Schnebly Hill formation, and everything in between. Recently, the Hermit and Schnebly have become independent in their own right, and the term "Supai" has become much more limited. Present predominantly on the Mogollon Rim, most of the Supai group is 325 to 285 million years old. Consisting of conglomerates, mudstones, marls and limestones, the members represent a range of depositional environments from near shore tributary and brackish, to fluvial and dune type sedimentation. The Supai group crosses the Pennslyvanian - Permian boundry, and in most areas directly underlies the Hermit Formation.


This is the internal workings of the abandoned Christopher Creek Uranium mine. Located across from the RC boyscout camp along highway 260, this locality has been a favorite for many years to collectors of fossil plant material along the Pennsylvanian - Permian boundry. The lower light tan formation is the Supai, and it is overlain by the Hermit Formation, marked by the redbed on the top. Fossils lie in carbonized beds of coal shale within the upper Supai. Many of the large tan blocks in the forground contain impressions of bark, and calemites trunks.

Here we are seen collecting plant material in the coal shale bed at the Christopher Creek Uranium mine. The Reddish layer towering above us is the Hermit Formation, and the weathering slopes below us are the Supai formaion. Typically, the remains of both Pennslyvanian and Permain carbonized plants are found, including Calemites and annularia, Walchia fronds, Pecopteris ferns, Spirorbis annelid worm shells, and much plant hash. We have also found shark coprolites and tiny bits of Permian petrified wood in portions of the quarry as well.

Just above Fossil Creek, the Supai lies in grey shale beds just below the Hermit Formation. This is one of the few areas that actual coal seams can be found in this formation. Here, the grey shales contain a foot wide layer of medium grade coal, in which the upper most layers touch shales containing plant fossils. This particular coal bed was used in palnology studies (fossil pollen) back in the 50's, and only contians stems impressions.

Just down the trail from the above site, another outcrop of Supai formation occurs. The basic grey carbonaceous shales are seen here, and the distinct bedding is powdery to the touch. several coal horizons appeared at this outcrop, each with a fossil plant bed in the shales above them.

Here, at the same Fossil Creek outcrop seen above, the author is seen enjoying the numerous fossil plant horizons in the grey shales. The beds range from nearly massive to highly fissile in nature. It was at this site we found an unusual occurence of Permian petrified wood.

Midgley Bridge in Sedona sits completely on the Supai formation. The grey shales and limestones and conglomerates that form this group have both massive and fine laminar bedding. Although we found this area devoid of fossils because of the rather coarse nature of the constituents, other areas contain excellent Permian\Pennsylvanian boundry plant fossils, including walchia, cordiates and calemites.

Just on the edge of the Midgley bridge in Sedona, the bridges foundation rests completely on the grey Supai formation. We found in this area, its massive nature formed resistant cliffs and protruding plates into the canyon below. The top surface of the formation is pockmarked, and contains many pools of water after a brisk rain.

Looking directly into the canyon spanned by the Midgley bridge in Sedona, the massive Supai formation, which contained much conglomeritic material is overlain by a spectacluar assemblage of other formations. To the left, the Bell Rock member of the Schnebly Hill formation, and to the right in the distance, the Coconino Sanstone also forms resistant cliffs.

Just past Midgley Bridge in Sedona, you encounter a huge road cut into the Supai formation. We parked our Jeep here for scale to show the massive layers interbedded with the finer shales. If you look carefully at the base, there is virtualy no scree slope or broken material. The Supai doesn't weather very fast, and usually will break off as one huge block at a time.

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