30 NEW YORK STATE MUSEUM 



other facts may be studied to best advantage by comparing the type 

 section here with those of the Little Falls and Trenton Falls dis- 

 tricts. The two last named sections may be found on page 38 of 

 the Remsen quadrangle bulletin.^ It is evident, therefore, that the 

 upper Trenton sea in the Port Leyden district was much clearer 

 water than the same sea in the Little Falls region. Also the 

 change from the upper Trenton to the Utica was much more 

 gradual at Little Falls as shown by the deposition there of the 

 Dolgeville shales as a transition series. In passing northward from 

 Sugar river to Martinsburg the pure, heavy bedded, crystalline lime- 

 stones assume even greater importance. 



The lowermost 20 feet of the Trenton are highly fossiliferous, 

 thin bedded, alternating shales and limestones. These beds are in 

 sharp contact with the underlying massive Black River limestone as 

 may be seen along Sugar river; along Black river i mile above the 

 mouth of Sugar river ; along Mill, Douglass, and House creeks and 

 Roaring brook. 



Except for the shale area at Locust Grove, the Trenton lime- 

 stone extends fro'm south to north across the map as an unbroken 

 belt whose width is from 2 to 3 miles. It forms the summit of the 

 lower great terrace so plainly shown on the topographic map. 

 Minor terraces are developed along the lines of outcrop of certain 

 harder and more resistant strata within the formation. The vil- 

 lages of Talcottville, Collinsville, Turin, Houseville and Martins- 

 burg all rest upon the Trenton. The larger streams have cut 

 picturesque gorges through this limestone as for example on Sugar 

 river, Mill creek. House creek and Roaring brook. The last named 

 gorge is locally called " Whitaker's gulf." 



Throughout all of Trenton time the ocean was fairly teeming with 

 animal forms, especially brachiopods, trilobites, cephalopods, corals 

 and crinoids. Many of the limestone beds are practically made up 

 of fossil shells. The writer has made no detailed study of the fos- 

 sils, but the forms are mostly the same as those decribed by Prosser 

 and Cumings from the type locality at Trenton Falls. Hall has 

 described and figured many of the forms from this limestone along 

 the Black river valley. In the lowest Trenton beds the writer has 

 seen specimens of orthoceras several feet long and 5 or 6 inches in 

 diameter. 



'N. Y. State Mus. Bui. 126. p. 38. 



