GEOLOGICAL PAPERS 99 



the exposures in the Cady quarry, the outcrops along Mill Creek 

 and the outcrops along Fancy Creek. Such a continuous section 

 aggregates a thickness of more than 150 feet. 



In the face of the Cady quarry 100 feet of brecciated, non- 

 fossiliferous limestone is revealed, representing the lower portion 

 of the Devonian section in this area. This exposure, which is 

 accessible to careful examination and study, is described in the 

 following section, designated Xo : 



SECTION OF ROCKS EXPOSED IX THE C.A.DV QUARHY. 



Feet. In. 



X:n. Loess and drift lO 



Nsm. Gray to yellow, soft fissile shale 2 



Nil. Dark, carbonaceous shale 8 



N:k. \'ery hard, brown to red, ironstained limestone, containing 

 many coralla of Phillipsastrea billingsi and shells of Atrypa 



reticularis 3 



X2J. Light gray to brown, much brecciated limestone, in layers 



2 inches to 3 feet thick 30 



N;i. Gray, brecciated, very irregularly jointed limestone, in im- 

 perfect layers 4 inches to 3 feet thick, with occasional chert 



nodules 15 



X:h. Hard, gray, fine-grained, brecciated limestone, in layers 2 

 inches to 3 feet thick, with conspicuous vertical joints, and 



occasional ribbon-like veins of calcite 30 



X:g. Xarrow band of hard, chocolate-colored, very fine-grained 

 limestone, with crevices along joints and bedding planes 



filled with calcite 6 



Xsf. Hard, dark gray, fine-grained limestone, with crystals of 



calcite common along the joints 3 



X:e. Band of hard, almost black, coarse-grained limestone i 



X':d. Soft, yellow, coarse-grained limestone, containing a distinct 



band of chert nodules near the middle 2 6 



X2C. Soft, blue, sandy to shale limestone, containing much calcite. 6 



X:b. Band of soft, dark gray to dark brown, fine-grained lime- 

 stone, in layers 2 to 4 inches thick, and containing many 



calcite crystals i 



X:a. \'ery hard, grayish brown, fine-grained brecciated limestone, 

 in layers 4 inches to 3 feet thick. Lamination planes con- 

 spicuous in the lower poi1:ion. To the bottom 15 



In the foregoing section the shale members (Nol and Xom) 

 represent the Pennsylvanian system, while the limestone members 

 (Xoa to Xok. inclusive), almost 100 feet in vertical thickness, 

 belong to the Devonian. Of the Devonian members exposed in 

 the quarry face, only the upper ten or fifteen feet may be seen 

 anywhere else in Rock Island county. These lower 100 feet of 

 Devonian strata are almost barren of fossils. Their correlation 

 with the Devonian rocks in other regions must be made on the 

 basis of their lithological character as revealed in this one 

 exposure. The most distinctive of these characters is the brec- 

 ciation which continues almost without interruption from the 

 base to the top of the barren lower layers. 



