Pierre Shale (USGS D1897) (Cretaceous of the United States)

Where: Niobrara County, Wyoming (43.3° N, 104.3° W: paleocoordinates 49.2° N, 71.6° W)

• coordinate estimated from map

• small collection-level geographic resolution

When: Red Bird Silty Member (Pierre Shale Formation), Campanian (83.6 - 72.1 Ma)

• bed-level stratigraphic resolution

Environment/lithology: offshore; lithified, concretionary, shelly/skeletal, brown, gray, yellow, silty, calcareous shale and limestone

• "shale; silty; weathers light gray; contains closely spaced yellowish-gray weathering to moderate-yellowish brown weathering ls concretions at base, smaller light gray weathering ls concretions 10 ft above base, and closely spaced, very fossiliferous ls concretions at top that weather light olive gray to moderate yellowish brown and contain veins of yellow calcite."
• "shale; silty; weathers light gray; contains closely spaced yellowish-gray weathering to moderate-yellowish brown weathering ls concretions at base, smaller light gray weathering ls concretions 10 ft above base, and closely spaced, very fossiliferous ls concretions at top that weather light olive gray to moderate yellowish brown and contain veins of yellow calcite."

Reposited in the USGS

Collection methods: mechanical,

• "[collected] from concretions at base"

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 1679: authorized by John Alroy, entered by Mike Sommers on 25.05.1999

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."
Bryozoa
  -
Bryozoa indet. Ehrenberg 1831
pyriporoid bryozoan
Bivalvia
 Myalinida - Inoceramidae
"Inoceramus subcompressus" = Cataceramus subcompressus
"Inoceramus subcompressus" = Cataceramus subcompressus Meek and Hayden 1860 clam
Cephalopoda
 Ammonitida - Baculitidae
Baculites perplexus Cobban 1962 ammonite
"(late form)"