﻿70 NEW YORK STATE MUSEUM 



rests either on the Potsdam or on the Precambric. In the upper 

 Black river valley it lies on the Precambric. All these formations 

 are capable of furnishing sandy material and hence the sandstone 

 base of the formation is but natural. The Theresa, however, is less 

 capable in this respect than are the other formations, thus account- 

 ing for the fact that this sandy base is a less prominent feature of 

 our area here than it is in the others. 



Hereabout, the best section of this basal material seen is at the 

 foot of the Pamelia inface, 2 miles east of Perch lake, Theresa 

 sheet. The small creek there runs over a massive, bared layer of 

 Theresa dolomite, above which a 14 inch layer of the same shows in 

 the bank. Above this lie weak, greenish sands and sandy shales, 

 with an exposed thickness of some 7 J / 2 feet, the basal layer some- 

 what pebbly and more massive than the remainder. The cement is 

 calcareous and abundant. The rock is therefore weak and seldom 

 exposed, yet in a sufficient number of places, and sufficiently well 

 to show that it everywhere underlies the limestone throughout the 

 district with a thickness of from 10 to 15 feet, much of which is 

 shaly. It is a more calcareous, and vastly weaker rock than even 

 the most calcareous beds* of the Potsdam, and quite different from 

 it lithologically ; so unlike in fact that the two rocks can be readily 

 distinguished from one another by lithologic character alone through- 

 out the whole region. This becomes of importance in the region 

 around Kingston, where in our opinion both sandstones are pres- 

 ent but without the separating Theresa formation. The Pamelia 

 basal sandstone rests, now on the Potsdam and now on the Pre- 

 cambric, is less shaly and attains greater thickness than on the 

 New York side, and shows at times astonishingly coarse basal 

 conglomerate. In its green color, weathering to a red mottling, 

 in its abundant calcareous cement, and in its weakness, it corre- 

 sponds exactly with the New York rock, while the silicious Pots- 

 dam beneath also corresponds with the Potsdam across the river in 

 every minute lithologic detail, even in the " tree " concretions. 



In the upper Black river valley both Potsdam and Theresa are 

 absent and the Pamelia rests on the Precambric. At Martinsburg 

 the wonderfully complete section shows a thickness of 19 feet for 

 the basal sandy portion, weak green sandstone, blotched with red, 

 abundant calcareous cement and with thin conglomerate at the base. 



Where thickest, the limestones of the lower division show, above 

 the basal sandstones, beds of gray, magnesian limestone with fre- 

 quent shale partings; these are followed upward by black, f os- 

 siferous limestones, holding a rather abundant marine fauna ; then 



