14 NEW YORK STATE MUSEUM 



LUDLOWVILLE SHALE 



This formation consists of beds of shale varying in character from 

 black and bituminous to light colored sandy and calcareous. Cal- 

 careous concretions are quite common, and 65 feet above the base 

 and near the top there are even layers of limestone one to two feet 

 thick. 



The Ludlowville shale is terminated at the top by the Tichenor 

 limestone. 



The basal hard layer, which is a coral reef at Centerfield, Ontario 

 county, and a calcareous sandstone in the Livonia shaft section, 

 is exposed at an old mill site on Little Conesus creek near the Avon 

 reservoir, but is almost entirely devoid of fossils. 



Along Gates creek two miles north of Aliens Hill 15 to 20 feet of 

 the shales next below the Tichenor limestone are exposed. 



This formation was named from its exposure along the shore of 

 Cayuga lake near Ludlowville, Tompkins county. It extends across 

 central and western New York and is everywhere richly fossilifer- 

 ous. Lists of the fossils composing its fauna may be found in 

 volume I of the Report of the State Geologist for 1893 and in State 

 Museum Bulletin 63. 



TICHENOR LIMESTONE 



A stratum of limestone about one foot in thickness overlies the 

 Ludlowville shale from Cayuga county to Lake Erie. It was known 

 by the geologists of the early State Survey as the Encrinal lime- 

 stone and serves as a bench mark in the stratigraphy of the western 

 part of the State. The name Encrinal limestone was applied tO' the 

 stratum on account of the abundance of crinoid fragments which it 

 contains and of which it is, at some localities, almost entirely com- 

 posed. 



A calcareous stratum of somewhat similar appearance to the 

 Tichenor limestone which occurs at the base of the Ludlowville shale 

 and outcrops at Centerfield on the Canandaigua quadrangle, on the 

 Attica quadrangle and other places in western New York, has some- 

 times been erroneously identified as the Encrinal, hence a more 

 specific name has proved desirable. The favorable exposure in 

 Tichenor gully on the west shore of Canandaigua lake suggested the 

 present name. A small exposure on Gates creek near the old mill- 

 dam is the only one on these quadrangles where Tichenor appears. 

 The following is a partial list of the fossils that occur in it : 



Phacops rana Green 

 Orthoceras caelamen Hall 



