Fossils
            from Lake Mary Road


            
Permian
            Kaibab Harrisburg Member


            
Expedition:
            8/22/2009

Updated 8/29/09
 

            
Introduction.

            
Formerly known
            as the Kaibab Alpha, the Harrisburg member contains by far the
            most abundant fossil assemblage in the formation. Most fossils
            are found moderately well preserved in a tan dolomitic limestone
            which strongly resists any acid. By either examining road cuts
            or cracking open the tan dolomites, you can find abundant mollusks
            such as gastropods, bivalves, and scaphopods, and sometimes huge
            wheelbarrow tire sized nautiloids. ( ! ) Excellent exposures
            of both upper Harrisburg and lower Fossil Mountain members can
            be found all along Lake Mary road on the way to Flagstaff. This
            documents one such site we visited, which on a previous expedition seemed very promising for finding both
            trilobites and huge nautiloids. We were not disappointed....



            
 One of the road cuts we
                  visited was rich in the tan dolomites. Since the cut was quite
                  broken up, many fossils are exposed along the breakage planes.
                  Additional cracking with a hammer of promising specimens usually
                  revealed an occasional rare Permian trilobite.
 
 A large Pectin, covered
                  with spines. The fossil is a negative mold of the mollusk.
 
 Long tapered scaphopod.
                  Once identified in older texts as "Dentalium", we now
                  believe that this is a new Kaibab specific species. Dentalium
                  has an open end for water flow. These do not.
 
 The rock break shows a
                  cross section of a large nautiloid. This is the outer whorl.
 
 The huge nautiloid I found,
                  which had obvious septa on the ends.
 
 Dawn finds a superb Anisopege
                  trilobite pygidum. It is probably "Anisopyge Mckeeii".
                  In the Permian, trilobites were nearly all gone. It is very
                  rare to find them in middle Permian sediments like these.
 
 Straparolus Gastropod internal
                  cast. We found one area with many poorly preserved specimens
                  and occasionally one very well preserved.
 
 Thallassenoides burrows.
                  These are the in filled domiciles of callanassid shrimp, these
                  were filled in with a high quartz gravelly in filling, indications
                  of a near shore environment in the tidal zone.
 
 Classic Y branching in
                  Thallassenoides.
 
 Another nice Straparolus
                  cast...
 
 Close up of unknown mollusk.
 
 Mollusk internal casts.
                  The fine details are missing making identifications nearly impossible,
                  but Id venture that the one on the left is a pectin.
 
 Here is the large nautiloid
                  I found, it is filled with tons of small shelly fossils!
 
 Close up on the end showing
                  the partitions in the shell - the septa.
 
 Dawn found this magnificent 2 inch Straparolus (Kaibabensis?)
                  gastropod, with excellent ornamentation on the whorls.
 
 Anisopyge McKeeii trilobite
                  pygidium. This close up shows the unusual narrow tapered appearance
                  of the pygidum which differs from the well rounded appearance
                  of the Mississippian Phillipsia we find in the Redwall.




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