No. 1. — A Section in the Trenton Limestone at Martinsburg, New York. 

 By Thomas H. Clark. 



Martinsburg is a small town situated in Lewis Co., N. Y., west 

 of the Adirondacks and east of Lake Ontario. It lies just within the 

 northwestern corner of the "Port Leyden quadrangle," the geology 

 of which has been described by Prof. W. J. Miller (N. Y. state mus. 

 Bull. 1910, 135). The \'illage is situated upon the upper of two 

 prominent terraces facing the Black River, and at an elevation of 

 about 500 feet above it. The contact of the Pre-Cambrian gneiss 

 with the sediments is along the western margin of the allu\ial plain 

 of the Black River, and the terraces are underlain by Ordo^dcian 

 limestone which dips gently westward. 



The summit floor of the terrace upon which Martinsburg stands 

 varies in width from one to two miles, and between it and the level 

 land along the Black River is a steep slope broken by a narrow but 

 pronounced shelf developed on the surface of the Black River lime- 

 stone. In this slope Roaring Brook has cut a deep trench, which 

 affords a fresh and almost continuous section of the Ordovician lime- 

 stone. The exposures along this brook make up the greater part 

 of the section here described, but as the rocks are largely concealed 

 along its upper stretches, outcrops along the road and old quarries 

 near the village of Martinsburg were also studied. 



In the Bulletin mentioned above, Miller has given a detailed section 

 of the strata below the Trenton, but concerning that formation he 

 gives no information beyond the estimate of 475 feet for the total 

 thickness. 



Dr. Ra^^nond visited this section in 1912, and has called attention 

 (Summary report Director Geol. survey. Department of mines, 

 Canada, for 1912, 1914, p. 345) to its importance in the correlation 

 of the Trenton of the typical section at Trenton Falls, N. Y., with 

 the supposedly equivalent deposits in Ontario. His work indicated 

 the desirability of more detailed study of the section, and at his 

 request I spent two weeks in the area in 1916, and visited it again for 

 a short time in 1917. 



THE SECTION. 



For convenience, the beds of the section will be described in ascend- 

 ing order. 



The hard cherty Black River limestone has resisted erosion more 



