Loc. 2. Road cut on the southern side of AR-Highway 66, ~1 km northeast of (Carboniferous of the United States)

Also known as loc. M-28 in Mapes, 1979

Where: Searcy County, Arkansas (35.8° N, 92.6° W: paleocoordinates 12.9° S, 34.6° W)

• coordinate estimated from map

• local area-level geographic resolution

When: Lower Member (Pitkin Formation), Chesterian (339.4 - 318.1 Ma)

• middle Chesterian; “The Lower Pitkin Member” contains a rich ammonoid assemblage, including Cravenoceras sp., Richardsonites richardsonianus, Eumorphoceras sp., Arcanoceras furnishi, Syngastrioceras sp., Metadimorphoceras aff. M. saleswheelense and Trizonoceras sp., and is assigned to the E1, upper Pendleian Stage (Saunders et al., 1977; Saunders and Work, 1999; Titus, 1999).

• group of beds-level stratigraphic resolution

Environment/lithology: reef, buildup or bioherm; lithified grainstone and lithified packstone

• deeper water than type 1 mounds
• This formation mostly comprises fossiliferous marine carbonates deposited in high-energy oolitic and bioclastic grain shoals along the shoreface into a southward-deepening ramp (Handford, 1986). According to the lithofacies analysis by Jehn and Young (1976), grainstones and pack-stones are dominant with minor amounts of shale, wackestone and biohermal limestone. The thickness of this formation is 15 m at the type section just north of the town of Woolsey in Washington County, Arkansas, but to the east the formation attains a thickness of more than 120 m (Easton, 1942, 1943). Saunders et al. (1977) subdivided this formation into two informal members with correlative discussions based on ammonoids.

Size class: macrofossils

Reposited in the OSU

Collection methods: peel or thin section,

Primary reference: S. Niko and R. H. Mapes. 2005. Early Carboniferous trigonoceratid nautilids from the Pitkin Formation of Arkansas, Midcontinent North America. Paleontological Research 9(3):233-241 [P. Wagner/P. Wagner]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 79627: authorized by Pete Wagner, entered by Pete Wagner on 14.03.2008

Creative Commons license: CC BY (attribution)

Taxonomic list

• See: Mapes R. H. 1979. Carboniferous and Permian Bactritoidea (Cephalopoda) in North America. The University of Kansas Paleontological Contributions, Article 64. p 1–75 pls. 1–41.
Cephalopoda
 Goniatitida - Glaphyritidae
Richardsonites richardsonianus Girty 1909 ammonite
 Goniatitida - Girtyoceratidae
Eumorphoceras bisulcatum Girty 1909 ammonite
 Nautilida - Trigonoceratidae
Stroboceras gordoni Niko and Mapes 2005 nautiloid
Epistroboceras pitkinense n. sp. Niko and Mapes 2005 nautiloid