364 P. E. Raymond — Fauna of the Cliazy Limestone. 



sandstone brought with it a part of the Gamarotwchia plena 

 fauna. The date of this invasion to the west can be rather 

 closely approximated. Cctmarotoechia plena, jRapkisioma 

 stamineum, and Malocystites murchisoni are found in the 

 middle of the section at L'Orignal. At Valcour Island these 

 species occur together in zone A 39 , 775 feet above the base, 

 thus showing that the formation in the Ottawa Valley repre- 

 sents the very latest part of Chazy time. 



Ulrich and Schuchert, in their paper on Paleozoic Seas and 

 Barriers,* bring out this idea of a Chazy sea invading westward 

 and southward. They state : " With the earlier part of this 

 subsidence [the Chazy invasion], the Atlantic invaded the 

 continent westward. . . . The typical Chazy formation . . . 

 bears evidence in its members of having encroached south- 

 ward and westward in the arms, the latest beds . . . extend- 

 ing farthest south and west." 



The Closing Period of Chazy Time. 



In the preceding pages an effort has been made to show 

 that in northeastern New York and in the Ottawa Valley, the 

 Chazy sea invaded over a land surface of Beekmantown rocks, 

 and that the base of the Chazy is a tangential sandstone ; also 

 that the invasion was first southward, covering the region of 

 the Champlain Yalley, and later westward along the locality 

 of the present Ottawa Yalley. f 



Of the former extent of the formation throughout the St. 

 Lawrence Valley or elsewhere, there is at present little evi- 

 dence. Since the sea did not attain the region of Aylmer 

 until very late Chazy time, it is probable that the formation 

 never extended much further west than the known outcrops 

 in that region (Allumette Island, etc.). 



From a study of the stratigraphy and faunas it becomes 

 evident that the upper portion of the Chazy is not represented 

 in the region south of Yalcour Island. Either these beds were 

 never deposited there or they were eroded before the Lowville 

 was laid down. The evidence is not of such a character as to 

 prove definitely which did occur, but for reasons given below 

 it seems more probable that the upper beds were deposited 

 south of Yalcour and later eroded. These reasons are as 

 follows : — 



*Rept. N. Y. State Pal., 1902, p. 639. 



[f By these terms, Chainplain Valley and Ottawa Valley, the writer does 

 not intend to convey the impression that the Chazy deposits were laid down 

 in narrow arms of the sea, or that the topograph} 7 was then anything lite 

 that of the present time. It should be remembered that strata of post-Chazy 

 age are involved in the Green Mountain uplift, and that there are indications 

 that the Adirondack^ did not exist in Ordovician time.] 



