It preserves fossils dating back to the Tournasian Age of the Carboniferous period.

It rests conformably on the Percha Shale and is overlain unconformably by the Lake Valley Limestone.

[1] The formation is locally abundant in fossils of Tournasian age,[1] with more than 200 marine invertebrate species reported.

[2] These include the ammonoids Pericyclus blairi, P. Cooperi P. costulatus, and Gattendorfia bransoni as well as Tournasian conodont and brachiopod faunas.

[2] The beds forming this unit were originally included in the Devonian Percha Shale, but were separated into their own formation by Laudon and Bowsher in 1941, when it was recognized that they are Mississippian in age.