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Nestled between two red beds of the upper Schnebly Hill Formation is a marine sequence consisting of a colorless gray and massively bedded limestone. The unit varies in thickness from about 100 feet at Fort Apache Arizona, and pinches out to zero west of Sedona. Most of these photos were taken in Sedona, where the thickness is approximately 10 to 20 feet. The Fort Apache Limestone is a Permian sequence representing a marine transgression onto the Schnebly Hill dunes which deposited a thin bed of limestone. Fossils are very scarce in this formation, in Strawberry for example, the massive beds visible on the north west end of town while driving north on Highway 87 are completely unfossiliferous. On the Indian reservation however, the typical Permian fossils are in abundance, including large brachiopods, sea urchin material, gastropods, and occasional cephalopods. There are few outcrops of this formation OFF the reservation which contain a few fossils however, and we have collected at these sites some remarkable marine invertebrates
Appearing as a distinct gray marker bed, the Fort Apache Limestone can be seen very clearly in this large hill just north west of the town of Strawberry. Just below it is the Schnebly Hill formation, an eolian sandstone deposit on to which the Fort Apache Sea transgressed.
In Sedona, down Schnebly Hill Road the Fort Apache outcrops once again in beautiful ledges and platforms extending from the rust red color of the underlying Schnebly Hill Formation. Here, I am standing on one of the ledges which we hiked out to to examine for fossils. Although the formation here turned out to be completely unfossiliferous, the distinctive bedding and beautiful canyons below were breathtaking.
From a distance, the Fort Apache Limestone forms a very obvious marker bed in the Permian Schnebly Hill formation. One can appreciate just how brief the transgression was by its apparent thinness here, onto the dune surfaces. This location allows some of the best access to the formation, and allows easy study.
My friend Vince Mele is standing on a bench of the Fort Apache Limestone, in Sedona up Schnebly Hill road. The underlying sandstone weathers easily, and often holes and cavities form underneath the limestone, making it a bit treacherous in places.
No less than six distinct beds of the Fort Apache Limestone appear here in this mid winter shot I took just after a dusting of snow. The location is down Tonto Creek road, just off of Highway 260 east of Payson. The land is all private here, and it unknown whether or not the limestone contained any fossils, since I was not able to get near to it. The adventurous could stop at the Tonto Fish Hatchery and examine the outcrop at closer range, which we have found can be found by a hiking trail from the hatchery parking lot.
In the summer, the view from near the Fish Hatchery on the Mogollon Rim is impressive. Numerous silicified microfossils near here have been recovered using acids to dissolve the limestones and leave a fossiliferous residue.
Close up from the Tonto Fish Hatchery parking lot. There is a hiking trail that takes you on top of this ledge, but no fossils were found here. |
