USGS D2121 [Pierre Shale] (Cretaceous of the United States)

Where: Niobrara County, Wyoming (43.3° N, 104.3° W: paleocoordinates 49.7° N, 79.1° W)

• coordinate estimated from map

• small collection-level geographic resolution

When: Baculites clinolobatus ammonoid zone, Pierre Shale Formation (Montana Group), Early/Lower Maastrichtian (70.6 - 66.0 Ma)

• AGE: Early Maastrichtian, on the basis of ammonoid biostratigraphy; Baculites clinolobatus zone.

• bed-level stratigraphic resolution

Environment/lithology: offshore; lithified, gray, silty, calcareous shale and limestone

• "Shale, silty. weathers light gray, contains numerous gray- and brown- weathering limestone concretions, some having fossils."

Size class: macrofossils

Reposited in the USGS

• "[collected] from concretions"

Primary reference: J. R. Gill, W. A. Cobban, and P. M. Kier. 1966. The Red Bird Section of the Upper Cretaceous Pierre Shale in Wyoming. United States Geological Survey Professional Paper 393-A:1-73 [J. Alroy/M. Sommers/A. Clement]more details

Purpose of describing collection: biostratigraphic analysis

PaleoDB collection 1575: authorized by John Alroy, entered by Mike Sommers on 17.05.1999

Creative Commons license: CC BY (attribution)

Taxonomic list

• "The fossils are ordinarily well-preserved. Most of the cephalopod shells and the inner nacreous layer of Inoceramus are aragonitic, especially specimens from above the Red Bird Silty Member. Shell material and specimens from the Red Bird member and the upper 50' of the underlying Mitten Member is partially transformed to calcite...Ammonites...of the [mid-upper third] of the Mitten Member are...entirely aragonite whereas shell material [of underlying material] is completely transformed to calcite."
Show authors, comments, and common names
Bryozoa
  -
Bryozoa indet.
Bryozoa indet. Ehrenberg 1831
pyriporoid bryozoan
Cephalopoda
 Ammonitida - Scaphitidae
Discoscaphites sp.
Discoscaphites sp. Meek 1870 ammonite
 Ammonitida - Baculitidae
Baculites clinolobatus
Baculites clinolobatus Elias 1933 ammonite
 Ammonitida - Sphenodiscidae
"Sphenodiscus cf. lenticularis" = Sphenodiscus lobatus
"Sphenodiscus cf. lenticularis" = Sphenodiscus lobatus Tuomey 1856 ammonite
originally entered as "Sphenodiscus cf. lenticularis"
Bivalvia
 Myalinida - Inoceramidae
Inoceramus balchii, ? Inoceramus fibrosus
? Inoceramus fibrosus Meek and Hayden 1857 clam
originally entered as "? Inoceramus fibrosus"