A shaley or glauconitic zone occurs in the lower portion and the base contains sand and conglomerate or breccia where the formation overlaps the Lamotte and lies directly on the granite of the mountain core.

[7] He described the lower part of that formation (now comprising the Bonneterre and the Elvins Group)[8] separately as the St. Joseph limestone.

[9] Charles Rollin Keyes's Fredericktown limestone included everything between the Lamotte and the Potosi Dolomite when he first described it in 1896, but his later uses of the name were in a more restricted sense equivalent to the modern Bonneterre.

Algal stromatolites, echinoderms, and microfossils such as Girvanella are associated with fringing reef paleoecosystems surrounding the Cambrian islands that are now the St. Francois Mountains.

[12] A variety of trilobite fossils have been reported from the Bonneterre, including Coosella, Holcacephalus, Meteoraspis, Tricrepicephalus, and Welleraspis.