GEOLOGIC MAP OF THE TULLY QUADRANGLE 



43 



the fauna. On behalf of a more exact basis for correlation we have 

 already proposed to restrict the term Marcellus shale to that part 

 of the series best exposed in the hill at Marcellus village. 1 This is 

 the lower portion of the mass and is well defined. At the base the 

 rock is a dark gray, somewhat calcareous and bituminous shale with 

 very thin layers of impure limestone. It gradually becomes less cal- 

 careous and a deeper black for a distance of 13 feet. Here appears 

 a stratum of hard bituminous limestone 2 feet and 6 inches in thick- 

 ness and this has been generally known as the Goniatite limestone 

 but which for precision of expression is better termed the Agonia- 

 tites limestone on account of the prevalence of the species Agonia- 

 tites ex p anus Vanuxem. This layer is a lentil in the Mar- 

 cellus shales though one of wide extent. Both below and above 

 the Agoniatites limestone the shales are densely black and bitumi- 

 nous to the top of the formation. In the upper layers are occasional 

 thin leaves of limestone and also rows of symmetrical subspherical 

 concretions from a few inches to 2 feet in diameter. At the top this 

 shale mass gradually becomes more argillaceous and lighter colored 

 and on the map the line of separation from the succeeding formation 

 indicates the horizon at which the black shale no longer constitutes 

 the larger proportion of the rock. The thickness of the entire mass is 

 100 feet. 



These Marcellus shales are. not well exposed in their entirety any- 

 where on this quadrangle though a small ravine on the west side of 

 Onondaga Valley 1 mile south of the north line of the map shows 

 the base of the section at 760 feet A. T. ; also the Agoniatites lime- 

 stone and a part of the upper black shales above. The limestone 

 outcrops in the Manlius road 2 miles east of Jamesville and the black 

 shales on the east slope of the same hill. There is a small outcrop 

 of the limestone on the brook that crosses this road at the next 

 four corners about 20 rods above the road. The limestone forms 

 the crest of a small cascade 40 rods south of the Manlius road in 

 Gifford's glen, a small ravine near the schoolhouse of district no. 8, 

 in the southwest corner of the town of Manlius, and }i mile within 

 the east line of this quadrangle. The limestone here is in three 



*N. Y. State Mns. Bui. 63. P.T4. 



