REPORT OF THE STATE rALEONTOLOGTST 1901 617 



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The Cashaqua shale was described as a " soft argillaceous 

 rock of a green color ... it contains flattened concretions 

 of impure limestone and sometimes of sandstone, but of these 

 it contains no continuous layers.-' It is favorabl}^ exposed 6 

 miles east of the Genesee gorge on Cashaqua creek and can be 

 easily traced westward to Lake Erie and eastward to Seneca 

 lake; throughout the entire distance it is found to overlie a 

 bed of black shale in w^hich fossils are exceedingly rare. In the 

 river section this bed is about 35 feet thick. This has been 

 termed the lower black band and is continuous and well de- 

 fined from the Naples valley on the west to Lake Erie, increas- 

 ing slowly in thickness. 



Next below, and overlying typical upper Genesee shale, are 

 4 to 6 feet of lighter colored shales and a few thin flags, the 

 whole bearing a much closer clastic and paleontologic resem- 

 blance to the Cashaqua shales than to the dark gray shales 

 bearing L u n u 1 i c a r d i u m fragile abundantly, on which 

 they rest. 



Overlying the Cashaqua beds occurs another thick mass of 

 densely black slaty shale, known as the second black band. It 

 is of the same character as, and coextensive with the lower 

 mass and like it increases in thickness toward the west, while 

 the Cashaqua shales decrease in that direction. These two 

 black bands are bench marks in the stratigraphy of the Portage 

 sections as their character is maintained and they are easily 

 recognized for more than one hundred miles east and west of 

 the typical section, while the other beds are variable in char- 

 acter and not to be distinguished without much care and study. 



The second of Hall's divisions, the " Gardeau shale and flag- 

 stones " was described (p. 227) as " a great development of green 

 and black shales with thin layers of sandstone." It includes 

 the second black band which is its basal stratum. The upper 

 limit was not definitely given, as the only change noted in the 

 character of the sedimentation is the increase of arenaceous 

 matter toward the top. " Towards the upper part the courses 



