Molluscan record from a Mid-Cretaceous borehole in Weston County, Wyoming

A core borehole in the Osage oilfield on the west flank of the Black Hills uplift in eastern Wyoming penetrated, in decending order, most of the Carlile Shale, all of the Greenhorn Formation, and the upper part of the underlying Belle Fourche Shale. Molluscan fossils are abundant in parts of the core and indicate an age span of early Coniacian to the middle Cenomanian. Most of the fossils are bivalves and ammonites; gastropods are scarce.

Fossils in the cores indicate the following zones:

Lower Coniacian
Cremnoceramus? waltersdorfensis
Upper Turonian
Scaphites coroensis
S. nigricollensis
S. whiifieldi
S. warreni
Middle Turonian
Collignoniceras woollgari
Lower Turonian
Mytiloides mytiloides
Mytiloides aff. M. duplicostatus
Upper Cenomanian
Sciponoceras gracile
Dunveganoceras albertense
D. pondi
Middle Cenomanian
Acanthoceras amphibolum