072 NEW YORK STATE MUSEUM 



down to a few inches in thickness. It was at first thought 

 that these thicker portions might mark an old stream channel 

 but a careful mapping of them failed to reveal any relation to 

 a possible stream course. Notwithstanding its rapid variation 

 in thickness it was found to be a remarkably persistent stratum 

 over the Olean and the eastern part of the Salamanca sheet 

 and was the key rock for determining the stratigraphy of much 

 of this region. Its maximum thickness of about 20 feet is 

 found in only a few localities and these are on Wolf creek. 

 Elsewhere in the Wolf creek region it is frequently found 5 to 

 10 feet thick, but over by far the larger part of the area in 

 which it is known to occur in these two quadrangles it is only 

 from a few inches to a foot or two thick and consequently is 

 not a conspicuous stratum and is rarely exposed in a natural 

 outcrop. Its horizon in numerous places is determinable only 

 by tracing up a hillside loose pieces on the surface to the 

 highest point at which they can be found and then working 

 along at this elevation till the upper limit of loose material 

 is well established. Even in a part of the region where it is, 

 as a rule, very inconspicuous it may for a short distance thicken 

 materially, as for instance northeast of Carrollton where it is 

 locally 10 or 12 feet thick, and it is entirely possible that in 

 the portion of the Salamanca quadrangle where it is not known 

 to occur and where its horizon is indicated by the dotted 

 geologic boundary line between the Chemung and the Cattarau- 

 gus there may be here and there spots where a few inches or a 

 few feet of it are to be found. The beds occasionally contain a 

 fair to good representation of marine fossils the assemblage of 

 which is characteristic of this horizon. It marks the first prom- 

 inent change in sedimentary conditions in the region and is re- 

 garded as a lentil marking the base of, and belonging to, the 

 Cattaraugus formation. 



Shales and sandstones. The deposition of the Wolf creek con- 

 glomerate was succeeded by conditions that caused the 

 deposition of bright red shales interbedded with green or 

 bluish shales and fine grained, greenish gray, thin bedded, 

 micaceous sandstones that together extend upward through 

 an average interval of 300 to 350 feet. This portion of the 

 stratigraphic column in which bright red shales occur, and 



