OCCURRENCE OF CARBONACEOUS MATERIAL IN THE 

 GREENFIELD MEMBER OF THE MONROE 



FORMATION. 



Charles W. Napper. 



At the Rucker quarries in Greenfield in southwestern Ohio, 

 is the largest and most important exposure of this member in the 

 Monroe formation. Above the water level of Paint Creek 

 there are 45 feet of stone, and quarrying has been conducted 

 as deep as 15 feet below this level. The entire vertical extent, 

 which is of the Greenfield member, is 60 feet. The rock is a 

 dolomitic limestone and is divided into two parts, the low^er 

 strata gray and the upper ones buff. The gra}^ is a hard, 

 solid limestone, while the buff, although firm, breaks more 

 easily under the hammer. In addition to the color the occur- 

 rence of carbonaceous material also serves to differentiate the 

 two parts. The Greenfield stone is of a very close texture and 

 with the exception of occasional masses having crevices, its 

 firmness, solidity and density are distinguishing characteristics. 

 The stone is rich in carbonaceous material which is disseminated 

 throughout its entire extent, as it has little opportunity to 

 collect in any large quantity. When the stone is freshly 

 broken this material gives it a bituminous odor which is a helpful 

 test in distinguishing this rock from other formations. 



The Gray Stone. — In the gray stone carbonaceous material 

 is evidenced in three ways in addition to the odor test. 



First. — In a thin ledge within a foot of its lowest worked 

 level this carbonaceous material is volatile. As pieces are 

 broken off it evaporates much the same as gasoline when 

 poured out. 



Second. — Throughout the gray stone carbonaceous material 

 manifests itself by the profusion of carbon lines. They are as 

 numerous as twenty or twenty-five to the inch. Their size 

 is similar to that of lines drawn with a fine pen point. They do 

 not occur at regular intervals; one inch will be full of them, 

 then a clear space of a fractional part of an inch, then more 

 lines. When they occur close together at intervals, they 

 give the rock the appearance of having a banded structure. 

 Usually they are parallel, and not often wavy unless bending 

 .around a quartz-lined cavity or a nodule of sphalerite. The 



'55 



