394 NEW YORK STATE MUSEUM 



unopposed current, seems to the writer to be conclusive.^ The 

 argument based on the thickness of sedinnents about the Adiron- 

 dacks, and their necessary wide overlapping on the gentle slopes 

 of the Precambric old land, also seems conclusive as to complete 

 submergence during the Utica, the thickmess and the evidence of 

 gentle land slope being ample to warrant the conclusion. If any 

 land remained during the Utica, it could have consisted of nothing 

 more than a few, low, insignificant islands, and such must have 

 been along the southern margin of the region. The slight amount 

 of Trenton submergence in the lower Mohawk region may well 

 indicate that, during a po^rtiou of Trenton time, there existed 

 here a shoal barrier between the eastern and western basins. 



The Utica was brought to a close by the shallowing of the waters, 

 which may well have brought a considerable part of the Adiron- 

 dacks, specially on the north, above sea level, though this is mainly 

 conjectural. During Lorraine time, which followed, a shoal was 

 developed in the region about Utica, probably extending thence 

 northeastward, which separated the eastern and western waters. 

 This would seem definitely to imply the emergence of land to the 

 northward, and likely by the close of the Lorraine a large part, if 

 not the whole of the Adirondacks, was elevated above sea level. 

 The following Medina, Clinton and Salina waters washed the west- 

 ern and southwestefn sides of the region only and may well have 

 somewhat encroached on its margins. Then came elevation on 

 the west, and the Helderberg depression on the east, the latter 

 probably involving the eastern border of the district. The suc- 

 ceeding Devonic deposits may have reached the southern rim of 

 the area, but could hardly have invaded it to any considerable 

 extent. 



Paleozoic igneous rocks. On both the eastern and southern mar- 

 gins of the Adirondack region, the Paleozoic rocks which fringe it 

 are found to be cut by igneous rocks, mainly in the dike form. In 

 the Champlain region these rocks cut, and are therefore younger 

 than, the Utica shale, the youngest of the Paleozoic rocks to be 

 found in the district. In the upper Mohawk district the dikes 

 also cut the Utica shale. 



'Am. Geol., June 1897 and February 1898, p.75. 



