190 F. W. SARDESON GALENA SERIES 



the use of lithologic basis for formational units, yet he adheres to the old 

 lithologic interpretation of the Galena as at Dubuque and proposes to 

 use it as the basis for a new classification. The demarcation below the 

 "Galena" is made the "Green shales" — a lithologic character — and Bain's 

 Platteville limestone is to include the green shale. In reality this step 

 which he now takes seems to be calculated to open the way for some one 

 to give a new formational name to the "Green shales" as lithologically a 

 formational unit, since the band of shale or "Green shales" as at Du- 

 buque, Iowa, when followed up into southeastern Minnesota, becomes as 

 great or even greater in thickness than is either the limestone below it or 

 the Galena above it. As is easily shown from faunal evidence, its bor- 

 ders run diagonally both downward and upward (see fig. 2) in relation 

 to the strata and faunal zone. Then, also, instead of forming a sharp 

 demarcation at their bo^mdaries, the shales graduate or alternate in strata 

 with the limestone just as the limestone and the dolomite also irregularly 

 graduate or alternate, rendering lithologic discrimination locally uncer- 

 tain as it is, also regionally unequal. 



The logical result of basing formational names on lithology in the 

 manner indicated is to give an irregularly variable scale rather than a 

 constant one. In the Galena series it appears to have been impractical in 

 the immediate past, tending more toward making the job last than to 

 bringing scientific results, and it promises nothing better for the imme- 

 diate future. It promises a practically diiferent result for stratigraphic 

 division in each district of the entire area of the Galena series' extent. 

 With imminent double system of geological reports before us, with over- 

 lapping quadrangles and counties, an increase in the confusion must be 

 anticipated. 



As said before, I am not prepared to state fully, but find evidence to 

 indicate that a very thorough lithologic interpretation or petrographic 

 and stratigraphic study of the Galena series might tend to produce much 

 the same conclusions regarding the formational units as have paleon- 

 tologic studies ; yet with the best application of lithologic method, namely, 

 with such careful scientific interpretation as petrographic study might 

 imply, it does not appear to me to promise a better basis for the deter- 

 mination of formational units than does the paleontologic evidence when 

 each is taken in conjunction with stratigraphy. 



Stratigraphic and paleontologic Classification 



Since the entire surface area of the Galena series had been one or 

 more times surveyed before my work on it began, there appeared to me 

 to exist at that time a ready means for establishing a uniform strati- 



