REPORT OF THE STATE PALEONTOLOGIST 1901 643 



This communication with the Atlantic through the St Law- 

 rence continuation of the Appalachian valley trough was, how- 

 ever, not of long duration, nor did the foreign element of the 

 Utica fauna impress itself to any appreciable extent in the 

 development of succeeding faunas of the Mississippian sea. A 

 slight elevation and it ceased, the preceding Trenton life condi- 

 tion being reestablished. 



The first deposits laid down in the Mississippian sea, 

 following the return to the Trenton arrangement of parts, 

 are the Frankfort shales, which we regard as equivalent Frankfort 

 to the Middle and Upper Utica of Nickles's Cincinnati section,^ 

 the typical Utica barely reaching that point, though something 

 like 300 feet thick in northwestern Ohio. 



The Lorraine sea extended eastward into the Mohawk valley 

 of New York only as far as Rome, being there limited by a low 

 north and south fold, that later on becomes conspicuous again 

 as the western limit of the Helderbergian invasion. The Lor- 

 raine of the Hudson river valley has been shown by Ruedemann 

 to be the equivalent of the Frankfort shales with a fauna transi- 

 tional from the Utica to the higher Lorraine. 



In the north the effect of the lateral compression to which the 

 Appalachian region was periodically subjected during the Pale- 

 ozoic is particularly marked in the area lying just east of the 

 Adirondack mountains. The Ordovician sediments here were Maximum of 

 piled in distorted and broken masses and largely covered by over- eaS^o^Ad?-"* 

 thrust Cambric deposits. As might be expected, the eastern one 

 of the two (Chazy and Levis) channels that intervened between 

 the Adirondacks and the Green mountains has been almost ob- 

 literated, so that it is now very difficult to trace out the relations 

 of the remnants of its deposits, which crop out only here and 

 there from beneath the overthrust masses of older rocks. Still, 

 with careful stratigraphic and paleontologic comparison, we 

 believe the task is not hopeless. Ruedemann's important results 

 about Albany, Ami's recent work at Quebec, and Dale's careful 

 areal work, look, to say the least, encouraging and augur even 

 greater results in the near future. 



* Cincinnati soc. nat hist. Jour.- 1902. 20:49^100. 



