c 



n 



Cashaqua 

 shale 



STRATIGRAPHY OF PORTAGE FORMATION BETWEEN 

 THE GENESEE VALLEY AND LAKE ERIE 



BY D. DANA LUTHER 

 With stratigraphic map 



Genesee valley 

 The Portage formation received its name " from its superior 

 development along the banks of the Genesee river in the dis- 

 trict formerly included in the town of Nunda, now Portage," 

 Livingston co. 1 The Genesee river is a northward-flowing 

 stream, rising just over the Pennsylvania line and completely 

 traversing the State to Lake Ontario. 



About 2V2 miles south of the north line of this town the valley 

 through which the river has flowed northward for 50 miles or 



more, ends, and the stream between ver- 

 tical cliffs 200 feet in hight enters a nar- 

 row rock gorge, plunges over three cascades 

 ESe respectively 76 feet, 110 feet and 66 feet 

 high, with rapids above, below and between 

 them, and descends about 350 feet in 2 

 miles, and 30 feet more to the north line of 

 Portage township; so that, including 187 

 feet of sandstone above the river at the 

 upper end of the gorge and 75 feet for the 

 southward dip, about 635 feet of strata are 

 exposed in the district referred to. 



The course of the river across the next 

 town north, Mount Morris, is through a 

 narrow canyon that broadens out to a 

 valley % to % mile wide, with steep banks 

 and vertical cliffs from 100 feet to 250 feet 

 high, and is about 6 miles long; this is fol- 

 lowed northward by another canyon with 



dark 



blue gray 

 shale with 

 concretions 



Styliola 

 limestone 



black shale 



pyrite layer 



Moscow shale vertical diffg? 15 q feet to gQQ feet Mgh? Qn 



at Moscow T t h o%?ro e fstyl a ia both sides, in which the river dashes from 

 ^tiTcL^ufs^ief orvis side to side till the mouth of the gorge is 

 reached at the village of Mount Morris, 11 miles in a straight 

 line, and about 15 miles if the course of the river channel is fol- 



1 Hall. Geol. N. Y. 4th Diet. 1843. 



