430 T. G. White— Original Trenton Rocks. 



Akt. LXI. — The Original Trenton Rocks ; by Theodoke G. 



White. 



[" The Faunas of the Upper Ordovician Strata at Trenton Falls, Oneida Co., N. Y." 

 Trans. N. Y. Acad. Sci., xv, 71-96, Pis. II— V.— Author's abstract.] 



This study is preliminary to a paper by the writer on the 

 Trenton formation in the Lake Champlain valley, in connec- 

 tion with which it was desirable to have a detailed description 

 of the type Trenton Falls section for comparison. As no such 

 tabulation had been published, nor even a statement of the 

 local geological boundaries of the original section, the writer 

 was obliged to go into the field for himself and the results 

 embraced in this paper were obtained. 



The type section extends from the bridge just below the 

 mill dam at Trenton Falls village to the bridge at Prospect, 

 abput two and a quarter miles along the gorge of West Canada 

 creek. In this distance the creek makes a total fall of over 

 312 feet. The dip of the strata is in the direction of the cur- 

 rent and averages less than 10°. Both above and below the 

 gorge in which the type section occurs, the strata are obscured 

 by heavy drift deposits, so that the beds adjacent to those out- 

 cropping in the gorge cannot be determined. Utica shale is 

 not found nearer than Nine Mile Creek, East Trenton, where 

 it is apparently faulted against the Trenton. The shaly layers 

 which form the transition to the Utica in other localities are 

 not represented, but presumably follow the coarse crystalline 

 limestone at the top of the gorge. The 325 feet of strata 

 embraced in the Trenton Falls section seem to include the 

 middle and the beginning of the upper part of the series of 

 strata comprised in the Trenton formation. They apparently 

 indicate a prolonged period during which there were frequent 

 oscillations of the land level, and consequently variable deposi- 

 tion, the waters at first rendered impure by silts but finally 

 clearing and furnishing large accumulations of purely frag- 

 mentary remains. In general the lower part of the formation, 

 as seen in the type section, is mostly shaly and is inclined to be 

 nodular, but the limestone increases in purity and becomes 

 crystalline in the higher layers. With the exception of the 

 gray crystalline beds at the top of the mass, the layers rarely 

 exceed one foot in thickness, and are usually two to six inches 

 thick, separated by more shaly layers. There are, however, 

 occasional conspicuous seams of compact blue-black limestone, 

 several feet thick, which continue very constant and hence 

 afford excellent datum levels in measuring the section. From 

 these heavy beds the best specimens of Asaphus are obtained, 



