218 



Report of the State Geologist. 



This part of the group is quite uniform in character throughout the dis- 

 trict, and maintains its thickness more persistently than the upper beds. The 

 strata aggregate about 400 feet in Onondaga county and are 233 feet thick at 

 Livonia. 



The upper part of these beds was termed by Professor Hall (1840), the 

 Ludlowville shales. 



These are succeeded by the Encrinal band, a formation of hard arenaceous 

 and calcareous shales in which a layer of hard grey limestone one to two feet 

 thick is interstratified. It receives its name from the large numbers of 

 crinoids, whole and fragmentary, that occur in it. It is not known east of 

 Cayuga lake and is much better developed from Seneca lake westward. 

 Drillers of salt wells usually notice this rock by reason of its hardness, which 

 is also the cause of its frequent exposure in the gullies. It is readily recog- 

 nized and for that reason and on account of its persistent character it is of 

 some importance as a bench-mark in the stratigraphy of the salt district. It 

 is favorably exposed at the mouth of Tichenor's gully on Canandaigua lake 

 and along the shore to the southward, also near the south line of West Bloom- 

 field, and in ravines on both sides of Genesee river north of Geneseo, near 

 Lin wood in the town of Pavilion, in a railroad cut two miles west of East 

 Bethany, on Murder creek at Griswold, at Darien, on Cayuga creek near 

 Elma, and at North Evans on the shore of lake Erie, and at many other 

 places. 



Although the Encrinal limestone does not occur in Onondaga and 

 Madison counties, the horizon is fairly well marked by a change in the 

 character of the shales which become more arenaceous and contain larere 

 numbers of well preserved fossils, which are so abundant in some places as to 

 form non-persistent calcareous layers of considerable extent, together with 

 rows of concretions that contain beautifullypreserved fossils. 



The shales are in thick beds, some of which are light or dark bluish-grey 

 and more or less calcareous, others are olive and sandy, and in the eastern 

 district a few layers of shaly olive or bluish sandstones are sufficiently firm to 

 be utilized for building purposes. On the slopes of the hill sides at the south 

 end of the valley of Onondaga creek these sandy layers appear, forming distinct 

 terraces, the softer intervening beds having been removed by denudation, and 

 they are exposed in similar escarpments near Delhi, and at other places. 



Twenty to thirty feet at the top of the group are dark brownish and 

 very soft shales that contain considerable iron pyrites and thin non-persistent 

 layers composed of masses of fossils. 



