STRATIGRAPHIC DELIMITATION OF ST. LOUIS FOR- 

 MATION 



CHARLES KEYES 



Were it not for the fortunate circumstance that our early Car- 

 bonic section of the Mississippi valley is already split up and its 

 long recognized geographic title Mississippian Formation restricted 

 in its application to a minor part more nearly coinciding with the 

 original proposal of the name, it is probable that this familiar term 

 would now have to give way to an older designation. In the sense 

 of a sub-periodic title St. Louis, or Louisian, has precedence by 

 many years over either Mississippi, or Mississippian. 



In the title St. Louis is focused the complete history of the dif- 

 ferentiation of the Paleozoic rocks of not only the Mississippi val- 

 ley, but of the American continent. 



At the time when the name first came into use as a geological 

 title St. Louis Limestone covered all the sequence of rocks lying 

 between the coal measures and the St. Peter sandstone. This pro- 

 cedure was a direct outcome of the first attempts to correlate the 

 Carbonic rocks of the Mississippi valley with the then recently es- 

 tablished section of England. Thomas NuttalP who had collected 

 extensively the fossils along the Mississippi river between Dubuque 

 and St. Louis, had found that the forms were similar to, or identical 

 with, those described from the Mountain Limestones of Derbyshire. 

 Although most of his collections were from the middle and southern 

 sections of his Mississippi River trip this explorer, who was pri- 

 marily a botanist and ornithologist, inferred that all of the lime- 

 stones which he had encountered were of the same age. This idea 

 seemed to be further supported by the presence of the lead deposits 

 in both Iowa and Missouri. It was this circumstance mainly which 

 later led Schoolcraft- to announce the parallelism of the Dubuque 

 dolomites and the Metalliferous (Carboniferous) limestones of 

 England. This, also, was the opinion of Featherstonaugh.-' Curi- 

 ously enough, the last mentioned author's elaborate discussion of 



'Journ. Acad. Nat. Sci. Philadelphia, Vol. II, pt. i, pp. 14-52, 1821. 



^Narrative Journal of Travels, etc., to Source of Mississippi, Cass Exped.. 

 414 pp., Albany, 1821. 



'Geol. Rept. Exam, made in 183 4 of Elevated Country between Missouri and 

 Red Rivers, 97 pp., 1835. (Twrenty-third Cong., 2nd Sess., House Exc. Doc. No. 

 115.) 



