GEOLOGIC MAP OF THE TULLY QUADRANGLE 



39 



of deposition and breaking with a conchoidal fracture. These beds 

 are seen, in the lower part, along the road leading south from James- 

 ville to the reservoir on the west side of Butternut creek and in the 

 cement beds in the Alvord quarries opposite the north end of the 

 reservoir on both sides ; also along the west side of Onondaga valley 

 in the rear of the cemetery north of Dorwin's Springs, at several 

 outcrops on the east side north of the reservation quarry, in the cliffs 

 at the Jamesville, Green lake and the White lakes and in the ravines 

 in the northeast corner of the quadrangle. In some of the blue layers 

 fossils are quite abundant and of these Leperditia alta, 

 S p i r i f e r v a n u x e m i , Strop heodonta v a r i - 

 striata are most common. There are also many large masses 

 of Stromatopora and Orthothetes interstriatus, 

 Whitfieldella laevis, W . sulcata, Holopea 

 a n t i q u a and T e ntaculites gyracanthus also occur 

 in this horizon. The two cement layers are nearly barren through- 

 out this region. Eurypterus r e m i p e s has been found at 

 Split Rock and at Manlius but has not been reported from this 

 quadrangle. 



DEVONIC 



Helderbergian limestone 



Between the top of the Manlius and the Oriskany sandstone is a 

 mass of limestone beds varying somewhat in appearance and attain- 

 ing a total thickness of about 40 feet. These are very dark blue 

 gray rocks weathering light bluish or ashen, in layers from 1 to iq 

 feet in thickness, some of these layers being laminated and splitting 

 readily along lines of deposition. Others are more compact and 

 have no regular fracture, being composed largely of masses of 

 Stromatopora and Favosites. These rocks were referred to the Hel- 

 derbergian limestones though it is not at present easy to correlate 

 them closely with the subdivisions of that series as developed in the 

 region of typical outcrops in eastern New York. The statement, 

 however, may be safely ventured that they are the westernmost rep- 

 resentatives of the lower deposits of that scries, viz the Coeymans 

 limestone and the New Scotland limestone. 



These beds are exposed in the Alvord quarries northwest of the 

 Jamesville reservoir, on both sides of the valley; also in the cliffs at 



