Iron ores of the clinton formation 19 



formity from place to place. Frequent changes in lithic character, 

 thickness and faunal contents are observable throughout their ex- 

 tent in New York State. 



In Niagara county, on the western end of the belt, limestone with 

 a smaller amount of shale constitutes the entire formation. Passing 

 through Orleans into Monroe county where the beds are again well 

 exposed, it is found that the shale predominates over the limestone, 

 a relation which holds true in a general way throughout the re- 

 mainder of the distance to Herkimer county. In Monroe county 

 the first hematite seam is encountered in outcrop, though it prob- 

 ably begins farther west. In Wayne and Cayuga counties there are 

 important changes with respect to the relative development of the 

 shales above and below the lower or main ore bed, while a second 

 hematite stratum accompanied by limestone makes its appearance. 

 Duplication of the ore seam is a common feature from here to 

 Oneida county. Within the interval included by Oswego, Onondaga 

 and Madison counties the shales attain even greater relative strength, 

 compared with the limestone. Throughout the middle part of the 

 belt, from Wayne to Madison counties, the lower ore bed lies but a 

 few feet above the Medina formation. In Oneida county, how- 

 ever, there is a very appreciable thickening of the basal green shale 

 which causes the ore to lie from 40 to 100 feet over the Medina. 

 Toward eastern Oneida county, the shale becomes quartzose, grad- 

 ing into thinly bedded sandstone with shaly layers. 



From Oneida county the stratigraphic bounds of the formation are 

 somewhat indefinite. It is particularly difficult to establish the upper 

 limits, since the extent of the Rochester beds above has not been 

 definitely ascertained. Recent paleontological investigations around 

 Clinton and east of there seem to indicate that the sandstone and 

 shale beds heretofore regarded as upper Clinton may belong to the 

 Rochester. The strata in Herkimer county are closely involved at 

 the base with the Oneida conglomerate and the exact line of demar- 

 cation between them has not, as yet, been satisfactorily determined. 



The stratigraphic succession along the belt will be shown more 

 in detail by a number of sections that have been prepared from 

 exposures and records of drill borings. The sections arc given in 

 order from west to cast. Attention may be called here to the 

 records of the lest holes recently put down in the portion of the belt 

 from Wayne to Oneida county given in detail in the chapter relat- 

 ing to exploration. 



