980 NEW YORK STATE MUSEUM 



At Olean rock city there are some traces of grits some forty 

 or more feet below the base of the Olean conglomerate. No- 

 where on this quadrangle, however, have such gritty beds been 

 found exposed in place and at several points good exposures of 

 this part of the section are to be seen, as for instance on the 

 road from Fourmile down into Fourmile creek valley. 



The trace of grit at the rock city may be the equivalent of one 

 or the other — probably the lower — of the two thin conglom- 

 erate beds found interbedded with shales and lying just beneath 

 the Olean conglomerate westward at Knapp's creek and else- 

 where on the Salamanca quadrangle, and which will presently 

 be described. If so, these coarser beds have so fined down and 

 lost their characteristics that it becomes impossible to separate 

 them on the Olean quadrangle from the Oswayo shales beneath 

 and both are on this quadrangle accordingly mapped together 

 under the name of the Oswayo. It is very probable that over 

 most of the small area on the Olean quadrangle where the 

 upper part of the Oswayo shale occurs the very topmost beds, 

 which are the equivalent of the grits and interbedded shales 

 westward, were eroded before the deposition of the Olean and 

 consequently that even if this part were lithologically separable 

 from the Oswayo there would be very little of it to map. 



Knapp beds 

 On the Salamanca quadrangle there are found beneath the 

 Olean conglomerate two thin conglomerates interbedded with 

 shales that are lithologically very similar to the underlying 

 Oswayo shales. These are doubtless in part at least the equiva- 

 lents of the grits and shales just beneath the Olean at rock city 

 and which are included in the Oswayo there but which evidently 

 thicken and coarsen westward till they are capable of differ- 

 entiation as the Knapp formation. These beds are not usually 

 well developed on the Salamanca quadrangle and have been 

 found in only a few areas along the southern edge. Southwest- 

 ward in Pennsylvania a more prominent conglomerate known as 

 the Subolean is situated in a similar stratigraphic position be- 

 neath the Olean from which it is separated by from 25 to 50 feet 

 of shales. It is known over a large area and extends according 

 to the Pennsylvania geologists westward into Ohio where it is 



