PORTAGE AND NUNDA QUADRANGLES 53 



In the early reports of the Geological Survey this black shale 

 band was considered as the upper part of the Genesee black slate. 

 In United State Geological Survey bulletin i6, 1885, J. M. Clarke, 

 for the reasons above stated, separated it from the Genesee slate 

 and considered it as a member of the Portage group under the 

 name *' Lower black band." In New York State Museum bulletin 

 63, 1904, it was designated the Middlesex shale, from its abundant 

 exposures in the town of Middlesex, Yates co., from which locality 

 it is continuous westward maintaining its general characteristics, 

 but diminishing in thickness to 6 feet on the shore of Lake Erie, 

 where it is well exposed in the bed of Pike creek near its mouth 

 in the town of North Evans, Erie co. 



The exposure of the Middlesex black shale in the cliff at the 

 mouth of the gorge is continuous in both banks for about 2 miles, 

 the dip bringing it down to the river level on the south side of the 

 '' Hogsback." Other outcrops may be seen in the lower part of the 

 ravine 2 miles northwest of Mount Morris, at the mouth of Buck 

 run ravine, and on Cashaqua creek at the foot of the cliff at Sonyea. 



Cashaqua shale 



The beds included in this division were first described in the 

 Third Annual Report on the Fourth District, 1838, as they appear 

 succeeding the Genesee black slate in Yates and Seneca counties. 



The name Cashaqua shales first appears on page 390 of the 

 Fourth Annual Report on the Fourth District for 1839, where it is 

 said : '' The group mentioned in the report of last year as suc- 

 ceeding the upper black slate, becomes on the Genesee a mass of 

 green crumbling shale of no feet thickness. It is exposed on 

 Cashaqua creek, hence the name Cashaqua shale." ^ 



In the final report of 1843, pages 226 and 227, after more fully 

 describing this division as it appears in the Genesee section, it is 

 added: ''At the eastern extremity of the district and on the shores 

 of Seneca lake at Penn-Yan and other places, this rock consists of 

 a green shale with thin flagstones and interlaminated sandy shale. 

 It contains the same fossils ; and holding the same position as on the 

 Genesee it can be regarded only as the same rock. . . . Farther 

 east it is not recognized as shale at all, the mass consisting of thinly 

 laminated sandstones." Tracing it west of the Genesee, it con- 



^ This Indian name derived from Gah-she-gwah, a soear, is also spelled 

 Coshaqua, Kishaqua, Kushaqua, Keshequa and Keshaqua. It is retained 

 here in the form used, by Hall which is the spelling adopted in the geological 

 literature of New York for 70 years. The word is pronounced Kish-e-quay. 



