282 NEW YORK STATE MUSEUM 



and magnesium carbonates in solution, with frequent storm 

 waters sweeping in sands from the adjacent land, and likelj a 

 climate of some aridity. That is, there must have been a land 

 barrier to the eastward separating the basin from the Atlantic, 

 and another to the westward shutting it off from the interior 

 sea, with a considerable Adirondack island in the midst of the 

 sea, on whose slopes the different beds of the formation over- 

 lapped as subsidence progressed. The whole subject is beset 

 with difficulty and needs thorough investigation, something that 

 it has not yet received. 



Because of the greater thickness of the formation in the Cham- 

 plain valley, and because the upper marine limestones occur 

 only there and on the north, it is reasonable to suppose that the 

 subsidence here opened a northeasterly connection with the sea, 

 whence the marine forms entered the basin. Likely at about the 

 same time subsidence ceased on the south and west and was not 

 improbably replaced by uplift, raising the region above sea level 

 and preventing the deposit of the marine limestones there. Such 

 an u;plift certainly occurred shortly after, and may well have 

 begun then. 



As a result of the ^Beekmantown subsidence and deposit, the 

 land area of the Adirondacks was much diminished in size; 

 though there still remained an area, mainly on the south and 

 west, which was not submerged. Then came the uplift, which 

 much increased the extent of this land to the south and west. 



Chazy formation. In the Champlain valley the Beekmantown 

 formation is overlain by a considerable thickness of mostly quite 

 pure, marine limestone beds containing abundant fossils. Fol- 

 lowed to the north into Canada, these deposits change into sands 

 and muds to a considerable extent, showing that a land area 

 which supplied this land wash must have existed in that direction. 

 How much of the present northern Adirondack region was over- 

 spread by the Chazy sea can not be told, but it would seem that 

 it must have been mainly submerged, since no land wash from 

 it reached the present Champlain valley region. Followed to 



