CONODONT BIOSTRATIGRAPHY AND MARKER BED CYCLES OF THE BURLINGTON TO KEOKUK CARBONATE STRATOTYPE IN IOWA, ILLINOIS, AND MISSOURI

Although the Keokuk and Burlington area is regarded to be the stratotype, the author uses the House Springs and Hollister sections because isostatic rebound on the inner craton left a hiatus for the Meppen lower Dolbee Creek.

The Burlington members begin with packstones of the masssive Meppen, which contains conodonts (Baxter) Polygnathus communus, Gnathadus typicus.

The Dolbee Creek has three cycles with coarse oolitic caps over silty wackestones and conodants Gnathodus typicus and Polygnathus communus and P. mehli.

Above is a dark, silty glauconite with Bactrongnathus distortus. The lower Haight Creek is three cycles of packstone with silty shale and a coarse cap. The upper Haight Creek has three light gray coarse cycles with Eotaphrus burlingtonensis.

Between the Haight Creek and Cedar Fork are two silty dolomites with a coarse white limestone between, CF/HC Dbl marker, and Eotaphrus burlingtonensis.

The Cedar Fork member has a oolitic limestone base, silty glauconite center and three thick, coarse cycles in the top with Cavusgnathus sp.

The Keokuk starts above a disconformity and is overlain by the Montrose chert and a thin fine limestone bed.

There are two thick coarse beds at the top of the Keokuk with Gnathodus texana.