64 NEW YORK STATE MUSEUM 



glomerate but also in the absence of the deep red, hematitic arkose 

 sandstones so abundant in the basal portion of the Potsdam in 

 Clinton county and on the north border of the Adirondacks. Alto- 

 gether the sandstone of this area resembles in its physical characters 

 more the middle and upper divisions of the Potsdam as distin- 

 guished in the typical sections at Keeseville and Potsdam by Van 

 Ingen and Gushing, than it does the lower portion. It is best ex- 

 posed at Port Henry in Bond's quarry above the Mineville railroad 

 track and in the cut of the Delaware and Hudson Railroad north 

 of the station. In the former place, as also along the upper Mc- 

 Kenzie brook, white and yellowish fine grained, partly heavy bedded 

 and partly slabby sandstones with occasional shaly bands prevail. 

 By universal cross bedding, floating large sand grains, ripple- 

 marked surfaces (beautifully displayed along McKenzie brook) 

 and intercalations of brecciated beds it is indicated that these 

 sandstones which would seem to correspond to the middle portion 

 of the Potsdam^ were deposited not far from the shore line. In 

 the railroad cut about 60 feet of whitish gray sandstone in one- 

 foot courses are exposed that present the typical and usual appear- 

 ance of the Potsdam sandstone. These beds are within a third of 

 a mile of the exposure of the Beekmantown beds at the tunnel and 

 since they dip in that direction, the interval of drift-filled valley is 

 inferred to be eroded in the remainder of the Potsdam series. 



The isolated exposure of Potsdam beds in the fault block at the 

 south end of the Westport Paleozoic area is again composed of 

 evenly bedded brownish, yellow and white sandstones corresponding 

 to the higher portions of the formation. About 100 feet of these 

 are exposed in the railroad cut. The third exposure of Potsdam 

 sandstone in the portion of the quadrangle here discussed is in the 

 village of Westport above the highway bridge and along the shore. 

 Only about 35 feet, consisting of whitish sandstone in one-foot beds 

 followed farther up by heavier beds of brown sandstone, are 

 exposed. 



While the evidence on the development of the Potsdam forma- 

 tion in the area under discussion, owing to its faulted and much 

 eroded condition is very incomplete and time was lacking for a 

 more exhaustive investigation of the formation, it seems fairly 

 certain that the lower Potsdam, and probably also the upper Pots- 



1 The reported finding of a sinall trilobite, probably Ptychoparia 

 m i n u t a , on upper McKenzie brook, may also indicate, however, the pres- 

 ence of beds equivalent to a part of the upper 350 feet of the Ausable 

 Chasm section, i. e. of upper Potsdam beds. 



