T. C. Brown — Shawangunk Conglomerate. 4c7S 



numerous cavities frequently lined with minute calcite crystals. 

 The transition from the underlying shale and to the overlying 

 limestone is gradual, not an abrupt contact. 



High Falls shale. — In the Binnewater outcrop the High 

 Falls shale is almost wholly a fine-grained, bright red shale 

 with subordinate green layers, approximately 68 feet thick. 

 In the gorge of the Rondont it consists of three easily 

 separated members, an upper shale, a middle sand, and a lower 

 shale. The upper shale member is predominantly green or 

 gray in color with a subordinate bed of dark red. The middle 

 sand is dark, almost black in color, and the lower shale is pre- 

 dominantly red, although much darker and less conspicuous 

 than the Binnewater outcrop. These three members can be 

 recognized in shaft 4, and in some of the core borings along 

 the Rondout tunnel line, but at a distance from the outcrop 

 the red color almost fails and is replaced by green or black. 

 The exposure of these beds in shaft 7 shows that the bands of 

 color do not always correspond to the bedding planes, and the 

 red color is evidently due to oxidation by surface waters. 

 Many of the beds are irregularly mottled green and red. The 

 transition from the underlying conglomerate and to the over- 

 lying sandstone is in each case where well exposed a gradual 

 change, not an abrupt contact or unconformity. In the 

 unweathered exposure of shaft 4, iron pyrite is present in con- 

 siderable amounts. 



Shawangunk conglomerate. — In the Binnewater outcrop this 

 is a thin conglomerate layer about ten feet thick. The various 

 shafts and borings along the tunnel line show that where it is 

 neither reduced nor increased in thickness by faulting or fold- 

 ing this formation varies from 174 to 284 feet. The lower 

 limit of the formation is a distinct unconformity. At the base 

 of the conglomerate there is always a layer of bright olive- 

 green shale varying in thickness from a few inches to several 

 feet. Similar green shale layers occur at several points within 

 the formation and vary from a few inches to a foot thick. 

 Occasional black partings a small fraction of an inch thick 

 occur. The conglomerate is slightly coarser grained at the 

 base and at the top, and at a few intermediate points, but 

 throughout the greater part of its thickness this formation is a 

 pure white quartz sandstone rather than a conglomerate. 

 Cross bedding on a small scale is common. The transition to 

 the shale above is rather gradual. Occasionally iron pyrite 

 occurs near the upper limit of the formation. 



A careful search during the excavation in these three forma- 

 tions failed to discover any trace of fossils. 



Conclusion. — These three formations evidently make up a 

 continuous and unbroken series, extending from the uncon- 

 formity at the base of the Shawangunk conglomerate up to, 



