The Maquoketa Shales. — James. 335 
among the roots of the mesquite bushes in rich and mellow 
soil, is soft and of abundant foliage and highly appreciated on 
account of its nutritious qualities. Gramma grass, is of a 
bluish green color, and though somewhat coarse is very nutri- 
tious and never becomes perfectly dry. Running mesquite 
and buffalo grass are both valuable pasture grasses, forming a 
dark turf extending over many acres. Both these grasses are 
exceedingly nutritious. The buffalo grass is said to revive af- 
ter a rain succeeding a drouth. 
Timber'. — The rivers and creeks are lined with pecan trees 
and these with mulberries, and plums often form extensive 
groves along their bottoms. Upon the large flats grows the 
mesquite, and the declivities of the hills support a growth of 
live oak and cedar. 
ON THE MAQUOKETA SHALES, AND THEIR CORRELA- 
TION WITH THE CINCINNATI GROUP OF SOUTH- 
WESTERN OHIO 
By Joseph F. James, M.Sc, U. S. Geological Survey. 
The term Maquoketa shales (pronounced Ma-quo '-ke-tah), 
was applied to an exposure of rocks of Lower Silurian age by 
Dr. C. A. White in 1870.' The character of the strata referred 
to this horizon and the reasons advanced for the introduction 
of the name, are found in Dr. White's report on the Geology 
of Iowa. The essential portions of his remarks upon this divi- 
sion of rocks are given below. He says f 
"Area and General Characters . — The surface occupied by this forma- 
tion is comprised within a singuhirly long and narrow area, seldom 
reaching more than a mile or two in width, but more than a hundred 
miles long within the state. It lies like a narrow sinuous band upon 
the surface between the regions occupied respectively by the Galena 
and Niagara limestones ; having, like them, a northwestward and 
southeastward trend. Its most southerly exposiire is in the bluffs of 
the Mississippi river near Bellevue, in Jackson county, and the most 
northerly one yet recognized is in the western part of Winneshiek 
county. 
"The whole formation is largely composed of bluish and brownish 
shales which weather into a tenacious clay upon the surface, and the 
soil derived from it is usually stilf and clayey. The shales are some- 
times slightly arenaceous, and sometimes calcareous bands ccmipose a 
considerable part of its bulk. The latter is the case at the typical 
localities on the Little Maquoketa river about twelve miles westward 
from Dubuque." 
^ Geology of Iowa, vol. 1. p. 180. 
2 Ibid, pp. 180-182. 
