IOWA ACADEMY OP SCIENCE 
147 
SUNDRY PROVINCIAL AND LOCAL PHASES OF THE GENERAL GEOLOGIC 
SECTION OP IOWA. 
By Charles Keyes. 
(Ahstract.) 
In the consideration of the broader taxonomic aspects of the general geologic 
section of the rocks of our state two features in particular at once arrest at- 
tention. 
One of these features is the completeness and discrimination with which the 
glacial deposits have been differentiated so that the Iowa sequence becomes 
the standard Pleistocene section for this country. This is one of the distinct' 
advancements recently made in American geology. For it credit is due mainly to 
workers in Iowa and especially to Iowa men. 
Contrasting strangely with this marked evidence of advancing knowledge is a 
feature which is of far greater general importance, which is stratigraphically 
of much greater value, which commercially has infinitely larger significance, and 
which in its infiuence reaches far beyond the boundaries of our state. Yet, 
in this field there has been almost no signs of progress. Compared with the 
similar work done in neighboring states it may be said that we have in this 
respect actually retrograded to notable extent. This feature is the differentia- 
tion and delimination of the stratigraphic and cartographic units-^the factors 
which make our geologic mapping possible and our understanding of the rela- 
tions of formations practically valuable. 
As is well known, it has long been the desire of paleontologists to have 
recognized a dual, classification of geologic formations — one to be expressed in 
time-units, the other in space-units. Of course, the first of these is to be based 
entirely upon a certain sequence of fossils. However, of late years, the tend- 
ency among actual field workers in geology has been towards the adoption of 
a single standard, the taxonomic ranks of the different subdivisions being de- 
termined by diverse characteristics in the same way that the systematic 
arrangements of animals and plants are effected. 
No general geologic section of Iowa rocks has ever been published that is 
strictly in accord with the plan mentioned. Instead, there has been an indes- 
criminate mingling of the two,, or of many classificatory standards. The imme- 
diate result has been to obscure rather than illuminate terranal relationships. 
Moreover, there has been little attempt at exact correlation of the various 
formations with those of other states. There has been neglect even in consider- 
ing the provincial correlations — an aspect of the subject which always should 
receive first attention. 
In the accompanying scheme of the geologic terranes of Iowa an attempt is 
made to keep the several classificatory criteria distinct and to use only the 
same feature in all cases of like ordinal rank. The dual standard is dispensed 
with. The time-element is only applied to those taxonomic groups where 
there is general concensus of opinion as to sufficient exactness. This extends now 
