GEOLOGIC MAP OF THE TULLY QUADRANGLE 



37 



on this quadrangle. At the Heard gypsum quarries in DeWitt, 

 north of the quadrangle boundary, they may be seen overlying the 

 Camillus shale and also in the abandoned Sweet quarry, 2 miles west 

 of Marcellus station. The horizon is characterized by the presence 

 in places of a great abundance of the crustaceans, Eurypterus, 

 Pterygotus, Eusarcus etc. These singular creatures which appear 

 to have attained the culmination of their development at this period 

 in the geologic history of New York are not found here so frequently 

 as at certain well defined localities to the east and west of this area, 

 namely at Jerusalem hill, Herkimer co. Union Springs, Cayuga co. 

 and Buffalo. Besides the remains of the Eurypterids there is an 

 abundance ofLeperditia scalar i.s Jones, a small Loxonema 

 and Lingula sp. but these fossils all appear to be of rare occurrence. 



Cobleskill dolomite 



Next in order comes a very hard, rather fine grained dark gray 

 limestone, here little altered by weathering, but farther west in the 

 State where it is commonly known as the " bullhead " ancl is less 

 pure, its color changes to a yellowish brown and it has a somewhat 

 mottled appearance. The shearing marks known as Siylolites 

 and small accretions of selenite and calcite crystals are common 

 throughout the mass. In some localities this formation is quite fos- 

 siliferous, 60 species having been reported by Hartnagel from Scho- 

 harie county, 30 from the dark limestone of Frontenac island in 

 Cayuga lake and 13 in the " bullhead " of Erie county. The low 

 level of the country over the northern part of this map affords no 

 favorable outcrops of this formation though it is unquestionably 

 present as indicated by the contour of the topography and probably 

 attains a thickness of about 6 feet. It appears however on Butternut 

 creek below Jamesville and is exposed at the top of the section at the 

 Heard gypsum quarry at DeWitt and at Browns falls on the west 

 branch of Limestone creek, i 1 /* miles southwest of Manlius. The 

 rock contains some fossils and the characteristic species are 

 Spirifer crisp us var. corallinensis Grabau, \Y h i t - 

 f i e 1 d e 1 1 a n u c 1 e o 1 a t a Hall, Chonetes jerseyen- 

 sis Weller and Strop heoclonta bipartita Hall. 



