4O NEW YORK STATE MUSEUM 



The rocks of the Schenectady formation contain a much greater 

 amount of sandstone beds than the other shale formations of New 

 York. Much of this sandstone occurs in thick banks, is somewhat 

 calcareous and much quarried as " bluestone." The hundredfold 

 alternation of these sandstone beds with the shales which persists 

 to a more or less extent throughout the whole formation is the most 

 notable lithic character of the eastern development. Numerous 

 sections which show- these endless alternations of sandstone which, 

 on account of its often coarse nature, is cited as grit, with slate, have 

 already been published by Mather in the First District Report 

 (pages 375-79), from the lower Mohawk and from Schoharie 

 county. We insert here as example a section which we have 

 measured in the abandoned quarries and the river bank at Aqueduct 

 and Rex ford near Schenectady, in descending order : 



1 Argillaceous shale 12' = 12' 



2 Grit banks, about I foot thick with shale 



intercalations J^ foot thick 9' = 21' 



3 Shale, argillaceous H" 22 ' 2 " 



4 Grit 3' 6"= 25' 8" 



5 Dark argillaceous shale 13' = 38' 8" 



6 Grit 6" = 39' 2" 



7 Shale 2' = 41' 2" 



8 Compact grit 6' = 47' 2" 



9 Shale 2' = 49' 2" 



10 Calcareous grit ("bluestone") 2' = 51' 2" 



11 Dark argillaceous shale 8' = 59' 2" 



12 Grit bed 6"= 59' 8" 



13 Dark shale, separated by fault from 



underlying beds 3' = 62' 8" 



14 Grit 6"= 63' 2" 



15 Shale, dark; argillaceous 2' = 65' 2" 



16 Thin bedded grit i' 6"= 66' 8" 



17 Bluestone 5' = 71' 8" 



1 8 Shale 2' = 73' 8" 



19 Bluestone i' 6"= 75' 2" 



20 Thin alternating beds of grit and shale, 



banded and wavy 2' = 77' 2" 



21 Compact beds of bluestone, with a few 



thin discontinuous shale seams. Beds 



irregular 9' 6" = 86' 8" 



22 Shale 4' 6"= 91' 2" 



23 Grit band with distinct plunge structure 6" 91' 8" 



24 Shale, dark, argillaceous 2' 6"= 94' 2" 



25 Grit bed with one shale seam 3' 6" = 97' 8" 



26 Shale, soft dark gray to black argilla- 



ceous and sandy shales 90' + = 187' 8" 



