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7 Ithaca Group 7 



Report for 1843 ^^^^ made the following classification: — 



Chemung group. ( Portage sandstone. 



Portage or Nunda group. I Gardeau flagstone. 

 Genesee slate. ( Cashaqua shale. 



TuUy limestone. I Moscow shales. 



Hamilton group I Encrinal limetone. 



^ Marcellus slate. ( Ivudlowville shales. 



Hall states as the reason for uniting the Ithaca and Chemung, 

 the impossibility of distinguishing them by any charadleristic 

 fossils. In the valley of the Genesee river Prof. Hall found the 

 three divisions of the Portage distincft and well marked, but 

 toward the south end of Cayuga lake he considered them scarce- 

 ly distinguishable. He considered the Portage fossils entirely 

 distincft from those above, and states* that he never saw one of 

 the Portage fossils in the higher group. As will be shown 

 later, this opinion was due to the lack of an intimate knowledge 

 of these faunas. 



The classification of the Upper Devonian in eastern New York 

 has been attended with much difficulty. The absence or scarcity 

 of fossils in much of the series in that part of the State made 

 its correlation with the well defined faunas to the west difficult 

 and uncertain. 



Vanuxem in 1840 recognized f a formation in the 3d Distridl 

 which he considered distin(5l from the Chemung and more re- 

 cent. He called this the " Montrose sandstone" from the town 

 of Montrose in Pennsylvania where it is well developed. 



Mather included all of the rocks of the Catskill mountains in 

 his "Catskill Mountain Series" which he subdivided as fol- 

 lows X : — 



I . Conglomerates and grits. 



!Red and gray grits with red shales mottled with green 

 spots. 

 Montrose sandstone of Prof. Vanuxem. 



3. Chemung group of Prof. Vanuxem. 



4. Ithaca group of Prof. Vanuxem. 



5. Sherburne flags. 



6. 



7. Hamilton group. 



8. Marcellus shales. 



*Geol. of N. Y., Part 4, p. 229, 1843. 



t4th Ann'l Rep't 3d Geol. Dist., p. 381, 1840. 



J 5th Ann'l Rep't ist Geol. Dist., p. 77, 1841. 



