46 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 palseontological 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. 



Sufficient 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 w T aters 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 



