ECONOMIC GEOLOGY 193 



The number of quarries is large and' can be increased in- 

 definitely, as nearly the whole area of the formation appears 

 to be capable of producing stone for flagging or for building. 

 The difficulty of indicating the division line between the Hamil- 

 ton and the Oneonta and the Hamilton and the Portage groups 

 of rocks makes it impossible to refer to localities more particul- 

 arly. The quarries near Cooperstown, and in the lake region, 

 particularly at Atwater, Trumanisburg, Watkins and Penn Yan 

 belong to the Hamilton group. 



Portage group 



In this is included the Oneonta sandstone, the limits of which 

 at the east can not be indicated; the flagstone beds of the Hud- 

 son valley and of the eastern part of the State continue up into 

 the Oneonta sandstone horizon. Many of the quarries are in the 

 latter formation. The more western and northwestern and higher 

 quarries are in it; and some of the Chenango county quarries also. 



The Portage rocks in the western part of the State consist of 

 shales at the base; then shales and flagstones; and the Portage 

 sandstone at the top. In the last division, thick beds with little 

 shale are marks of this horizon. The stone is generally fine- 

 grained. The quarries near Portage and near Warsaw are in it; 

 also the quarries at Laona and Westfield in Chautauqua county. 



Although not of as great extent in its outcrop as the Hamilton 

 group, the Portage rocks are developed to a thickness of several 

 hundred feet along the Genesee river at Mount Morris and at 

 Portage; and form a belt having a breadth of several miles 

 through Tompkins, Schuyler, Yates, Ontario and Livingston coun- 

 ties, and thence west to Lake Erie. The formation is capable of 

 supplying an immense amount of good building stone and flag- 

 stone throughout its undeveloped territory. 



Chemung group 



The rocks of the Chemung group crop out in the southern tier 

 of counties, from Lake Erie eastward to the Susquehanna. The 

 shales are in excess of the sandstones in many outcrops, and there 



