A6 GEOLOGICAL RECONNOISSANCE 
that variety of tint so agreeable to the eye, and so much esteemed by the 
worker in marble. 
In the middle and north-west part of Marion county, these marble layers 
lie high in the hills; generally 20 to 50 feet below the tops of the ridges 
in which they occur. 
In the high Pine ridge, which forms the water-shed between Sugar-loaf, 
Crooked, George’s, and Jennings’ creeks, there is a considerable mass of 
chert capping its summit, which is, probably, referable to the subcarbo- 
niferous period; judging from the few casts of crinoidea observed in it. 
This ridge is, at least, 200 to 250 feet higher than the subordinate ridges 
bounding the water courses of Sugar-loaf creek. 
The summit of this high ridge is composed of chert sandstone, under- 
laid by limestones, dolomitic and calciferous sand-rock. 
The siliceous soil, in which the pine trees flourish, is derived from the 
chert and sandstone, on which it is based. 
The above-described marble rocks, which occur in these ridges, are, 
probably, the representative of the so-called “Cooper marble,”-of Missouri 
which has been referred to the age of the Onondaga limestone of the New 
York system. 
At present, we have not sufficient paleontological evidence to decide 
on its exact equivalency with rocks of other states; but in the future 
progress of the survey, further light will, no doubt, be thrown on the age 
of these beds, which intervene between the subcarboniferous and silurian 
rocks of northern Arkansas, and which, on account of their economical 
value, are of great interest. 
Suificient evidence has already been obtained to establish the age of 
the 300 feet of magnesian limestones and silico-calcareous rock, that 
underlie the marble strata, forming about 250 to 300 feet of the lower and 
main body of the ridges of Marion county, as of lower silurian date, and, 
in all probability, to that subdivision known as the calciferous sandrock of 
the New York system. This is the lead and zinc-bearing formation of 
north-western Arkansas. 
Sulphuret of lead, or galena, has been found, more or less abundantly, 
at numerous localities, both in Marion and Carroll counties. The most 
noted ones, in the former county, are on the waters of Sugar-loaf, High- 
tower, and Jennings’ creeks. No regular or systematic mining operations 
have yet been undertaken in Marion county, so that an opinion of the 
exact character and dimensions of these mineral deposits, cannot be 
formed; they occur, however, evidently, much in the same manner as 
those which were subsequently examined in the eastern part of Carroll 
county, at the Coka and Mitchell diggings. One partial drift, and a few 
