Popes Creek (Johns Hopkins collection) (Eocene of the United States)

Where: Charles County, Maryland (38.4° N, 77.0° W: paleocoordinates 38.8° N, 61.1° W)

• coordinate based on nearby landmark

• outcrop-level geographic resolution

When: Woodstock Member (Nanjemoy Formation), Ypresian (56.0 - 47.8 Ma)

• STRATIGRAPHIC RELATIONS: From the Woodstock Greensand Marl Mbr of the Nanjemoy Fm, Pamunkey Gp. Eocene, according to Miller (1947); Early Eocene, according to Ward (1985). STRATIGRAPHIC POSITION: From upper part of member.

• bed-level stratigraphic resolution

Environment/lithology: transition zone or lower shoreface; poorly lithified, glauconitic, micaceous, black, green, silty sandstone

• ENVIRONMENT: The larger, diverse molluscan fauna in the Woodstock, compared with the nondiverse Potapaco assemblages, suggest a return to more open-marine, shallow-shelf conditions (Ward, 1985). The foraminiferal assemblages indicate an inner sublittoral paleoenvironment with water depths of about 20-40 m during deposition of the lower and middle parts of the unit and an inner sublittoral (40-60 m) environment with firm, sandy substrates during deposition of the upper part. The abundance of Turrilina and Fursenkoina, which are among the predominant benthic genera in the middle part of the unit, suggests waters containing lower than normal dissolved oxygen. The somewhat coarser, much more lignitic, pebbly sands of the Woodstock, the relatively shallow water depths, and the microfauna suggest a perideltaic environment. Dinocyst assemblages throughout the Nanjemoy in the Haynesville cores are dominated by peridiniacean taxa and thus represent predominantly estuarine to inner neritic environments.
• SPECIFIC LITHOLOGY: Sand, olive-black (5 Y 2/1), very fine, silty, micaceous, well-sorted, very glauconitic; numerous well-preserved mollusks; upper contact sharp and burrowed; burrows extend as much as 3 feet downward. LITHIFICATION: Poorly ;ithified, based on facies description and figured specimens.

Size class: macrofossils

Collection methods: COLLECTORS: Unknown collector. REPOSITORY: Johns Hopkins University.

Primary reference: W. B. Clark and G. C. Martin. 1901. Mollusca. Maryland Geological Survey, Eocene 122-203 [M. Clapham/M. Clapham]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 81880: authorized by Austin Hendy, entered by Austin Hendy on 17.07.2008, edited by Mark Uhen and Matthew Clapham

Creative Commons license: CC BY (attribution)

Taxonomic list

• COVERAGE: Limited to Nautiloidea described in primary publication. NOMENCLATURE: Authoritative publication with modern nomenclature and species-resolution identifications.
Bivalvia
 Carditida - Carditidae
Gastropoda
 Sorbeoconcha - Turritellidae
Cephalopoda
 Nautilida - Hercoglossidae
Hercoglossa tuomeyi n. sp. Clark and Martin 1901 nautiloid
Cimomia marylandensis n. sp.2 Miller and Thompson 1933 nautiloid
Part of Hercoglossa tuomeyi Clark & Martin
Chondrichthyes
 Lamniformes - Lamnidae
Carcharodon sp.1 Smith 1838 white shark
 Lamniformes - Odontaspididae
Odontaspis macrota1 Agassiz 1843 sand tiger shark
Aetobatus
  - Aetobatidae
Aetobatis irregularis1 Agassiz 1843