THE AGE OF ANTHRACOLITHIC ROCKS 7iL 
STRATIGRAPHIC CONSIDERATIONS 
Several years ago it was discovered that the Cherokee shales were 
not the oldest deposits of the western Coal Measures or Pennsylvanian 
rocks. While it was known that the unconformity between these 
shales and the Mississippian rocks below was a profound one, yet 
its true significance was not realized until the discovery in Arkansas 
and eastern Oklahoma of a great series of underlying rocks of Pennsyl- 
vanian—Lower Coal Measures—age. ‘The result of the discovery is 
to restore the Lower Coal Measures to the trans-Mississippi section, 
leaving the Cherokee shales and perhaps some associated strata 
representing the Middle Coal Measures—“ Middle Upper Carbon- 
iferous” of European geologists—of Europe. 
While this latter fact has been determined largely by paleo- 
botanic' evidence and that derived from the cephalopods? it is 
believed that the trend of the evidence furnished by the invertebrates 
is, in general, in the same direction. 
The Cherokee shales are a thick (400-500 feet) series of shales 
with some sandstones and coal, on the whole unfavorable. to the 
existence of clear-water marine faunas. Indeed much of the region 
stood at about sea-level for considerable lengths of time, as is evident 
from the plant remains and coal deposits distributed through the 
rocks as well as by ripplemarks and other physical evidence. 
However, marine conditions and faunas appeared especially during 
its later history. 
Following the deposition of the Cherokee shales the sea trans- 
gressed and the Fort Scott limestone was deposited. ‘This limestone 
is of considerable thickness and carries a rich marine invertebrate 
fauna. Following. the Fort Scott limestone there occurred rythmic 
recessions and transgressions of the clearer marine waters through- 
out the Kansas region, resulting in the deposition of alternate clay 
shales and limestones with, rarely, fine sandstones and coal. The 
shales vary from 4o feet to 200 or more feet in thickness, and the 
limestones from two to 4o or 50 feet in thickness. The shales are 
clayey, sometimes carrying considerable fine sand, and are gray to 
1 David White, Mon. XX XVII, U.S. Geological Survey, 1899. 
2J. P. Smith, Mon. XLII, U. S. Geological Survey, 1903. 
