The Geologic Column of St. Louis, Mo.

The rock formations that are shaded at top are those that can be found on the surface in St. Louis City or County. Information for sub-surface strata comes from a Laclede Gas Company well in Florissant. This is taken from a diagram by James A. Martin and George E. Heim of the Missouri Geological Survey and Water Resources (1958, Rolla, Missouri). Also [See complete diagram] (215 K) for cross section from Eureka to Mississippi River at Alton.

[Note: Two rock formations were not labled in the below diagram. The first being rocks of the Chesterian series. Chesterian Limestones in were discovered in northeastern St. Louis county during the late 1970's by
the Scott K. Williams from an exposure in Coal Bank Creek.  On the below diagram, it should be shown as located on top of the St. Louis limestone, immediately below the Pennsylvanian. The second formation not labeled is the Grassy Creek formation. It should be below the Chouteau and above the Maquoketa.]
 

Pennsylvanian Period:

Mississippian Period:

Chesterian Series
St. Louis Limestone
Ste. Genevieve
Spergen
Warsaw
Fern Glen
Burlington
Keokuk
Chouteau
 

Devonian

395,000,000 to 345,000,000 years ago.*

Grassy Creek Fm.
 

Silurian

Maquoketa
 

Ordovician

Kimmswick
Plattin-Decorah
Joachim
St. Peter (deposited 450 million years ago)
Cotter
Jefferson City
Roubidoux
Gasconade
 

Cambrian

Eminence (Potosi-Eminence formations deposited approx. 520 million years ago)
Potosi
Elvins Group (Derby-Doe Run, Davis fms.)
Bonneterre (deposited 550 million years ago)
Lamotte Sandstone
 

PreCambrian

("Butler Hill "Granite, rhylolites, basaltic dikes, ect.) (2 billion to approx. 900 million years ago*)

Notes:
* based on Potassium Argon dating.