MISSISSIPPIAN. 

 Correlation table oftJie Paleozoic formations in northern ArTcansas [in part]. 



411 



Adams ^ describes these formations as follows : 



The Noel shale [now called the Chattanooga shale] has been previously described by the 

 Arkansas State Survey under the name of the "Eureka shale;" but this name is preoccupied 

 by the Eureka quartzite of Nevada, and accordingly it has been renamed, from the town of 

 Noel, in southeastern Missouri, where it has been studied and at which place it is typically 

 exposed. It consists of a bed varying from a few feet, and in some cases a few inches, up to 

 70 feet in thickness. Usually it averages from 15 to 30 feet. Its color is often black, although 

 not infrequently it has a greenish and sometimes a yellowish appearance, according to the 

 conditions of weathering or the amount of carbonaceous material contained in it. 



The Noel shale is succeeded by the Boone formation, which appears to be conformable 

 with it and represents merely a change in the character of sedimentation. Over a large area 

 its basal member is an even-bedded limestone, free from chert and showing in a distinct ledge, 

 sometimes shelly and thin bedded. It is known as the St. Joe limestone member. Its thick- 

 ness in northern Arkansas varies from a few feet up to 50 feet. * * * 



The remaining portion of the Boone formation consists of beds of cherty limestone and 

 beds of chert, which vary in their lateral and vertical extent in such a way that it has been 

 impossible to divide this part of the formation into members which can be generally recognized. 

 The thickness of the formation is about 325 feet. 



The limestones of the upper portion of the Boone formation are often coarsely crystalline 

 and have usually a light-gray color. They contain numerous well-preserved fossils, but crinoid 

 stems are perhaps the most conspicuous. 



Generally the upper portion of the formation is heavily bedded, and the lower portion 

 contains a large amount of flint. The line separating the St. Joe member from the remaining 

 portion, although not marked by any very evident stratigraphic break, has been drawn at the 

 point where the chert appears and is at a definite horizon. 



In the vicinity of Batesville there is a bed of shale lying upon the Boone limestone and 

 chert. It is well exposed around Moorefield, from which place it is named. In that locality 

 it has a thickness of from 50 to 75 feet. To the west, at Marshall, it is not over 35 feet thick, 

 and evidently it does not extend much farther westward. The shale has a light-grayish or 

 bluish color, and is very friable. In places it is sandy. 



The Moorefield shale is succeeded at Batesville by sandstones with some interbedded 

 shale. In certain localities to the west the formation contains interstratified limestones, which. 



