T. C. Brown — Shawangunk Conglomerate. 471 



these beds in an unaltered condition. Furthermore, the fresh 

 cut made it possible in every case to observe the contacts or 

 transitions between formations. 



In shaft 8, only the lower thirty feet of the Shawangunk 

 conglomerate was penetrated ; all the higher beds were cut out 

 by an overthrust fault which brought the Hudson River shale 

 to rest upon this lower part of the conglomerate (see fig. 2). 

 The lower contact of the conglomerate with the Hudson River 

 shale was distinctly shown, and it was a distinct erosional un- 

 conformity. The irregular contact rose nearly four feet over 

 a rounded projecting mass of shale at the center of the shaft. 

 At the base of the conglomerate was a thin layer of 

 bright green or olive-green shale. The first few feet of the 

 conglomerate consisted of large quartz pebbles up to two 

 inches in diameter in a dark matrix. Above this it became 

 pure white in color and was largely sandy in texture. 



Shaft 7 penetrated 35 feet of drift, mostly finely laminated 

 clay, 54 feet of High Falls shale, and 174 feet of Shawangunk 

 conglomerate, and then entered the Hudson River shale. At 

 this point the High Falls shale consisted of alternating bands 

 of red and green, the red predominating. The bands of color 

 did not always correspond with the bedding planes ; the red 

 color seemed to be due rather to the action of oxidizing 

 waters. Many of the larger masses of rock brought out dur- 

 ing the excavation of the shaft were mottled with red and 

 green in an irregular manner. 



The transition from the conglomerate to the shale was 

 clearly shown in this shaft and it was a rather gradual one. 

 The upper six or eight feet of the conglomerate consisted of 

 quartz pebbles in a dark shaly matrix. Above this came two 

 feet of mingled red and green shales containing numerous 

 quartz pebbles. The quartz pebbles decreased in number 

 from the bottom to the top of this two-foot layer, completely 

 failing in the overlying shale. One rather remarkable feature 

 about these pebbles was that they were larger than the aver- 

 age size of the pebbles in the conglomerate below. The 

 transition, however, was a gradual one and there could be no 

 gap in the record as suggested by Hartnagel. 



The lower contact of the Shawangunk conglomerate with 

 the Hudson River shale was also well shown ; it was in a fresh 

 and undisturbed condition. A thin layer of bright olive-green 

 shale occurs at the base of the conglomerate and unconform- 

 able with the underlying shale. 



Shaft 6 passed through 26 feet of drift consisting of bowl- 

 der clay or till with numerous large bowlders and many peb- 

 bles. Then it penetrated the Shawangunk conglomerate with 

 a thickness of 277 feet. The upper surface had suffered 

 glacial erosion and possibly a few feet of conglomerate may 



