216 



Report of the State Geologist. 



three rods wide and from one to five feet in height. Their axes have generally an 

 east and west direction, but they are not straight and are very rarely parallel 

 to each other. When not covered by the drift, it is plainly evident that they 

 are anticlinal folds formed subsequent to the glacial epoch. 



The salt beds have not been found to extend as far north as the line of 

 outcrop of the Onondaga limestone, though approaching very near to it west 

 of the Genesee river. In the eastern counties of the district they have not 

 been found nearer than ten or fifteen miles south of the line of the Helderberg 

 escarpment. 



Hamilton Group. Next in order of upward succession are the argillace- 

 ous and sandy shales and thin limestones of the Hamilton period, at the base 

 of which is the Marcellus shale. This formation is 150 to 200 feet thick in 

 Onondaga county, where it has its greatest development. It diminishes 

 toward the west, and is not more than sixty feet thick in the western part of 

 Genesee county. 



The contact line with the light grey Onondaga limestone is very distinctly 

 marked by the abrupt change to black calcareous shales, or soft, thinly 

 laminated, blue black limestone in a bed one to three feet thick that is 

 succeded by a bed of fetid bituminous black shales, containing two or three 

 rows of spherical concretions or septaria, from a few inches to two feet in 

 diameter. 



A stratum of dark grey, compact limestone one-half to three feet thick 

 is interstratified with the black shales, and is known as the Goniatite lime- 

 stone on account of the fine specimens of Goniatites Vanuxemi which it con- 

 tains. As this rock is well exposed two miles west of the village of Manlius, 

 it has sometimes been called the Manlius limestone. At Marcellus it is two 

 and one-half feet thick and thirteen feet above the Onondaga limestone. 



In the western part of the district a dark chocolate-colored limestone 

 occupies a similar position in the strata, but carries a wholly different associa- 

 tion of fossils. This has been termed the Stafford limestone. 



It is well exposed at Le Roy in the east bank of Oatka Creek, where it is 

 one foot eight inches thick and 29 feet above the Onondaga. Though it 

 abounds in fossils, the goniatites are not in so good condition in the western 

 part of the district. The intervening bed of black shale with concretions may 

 also be seen to good advantage in the bed of the stream above the railroad 

 bridges. 



