R I ES — G Ko LOGY OF OrANG E Co (J NT Y. 



401 



ferry. In the single exposure known, this rock is a dark blue-grey, shaly 

 limestone, containing abundant crinoid stems and several Trenton species. 

 The rock strikes N. 35° E. and dips 40° E. 



Hudson River Slates. Two-thirds of Orange county is underlaid by 

 the members of this formation, which cover nearly the entire area of the 

 townships of Mt. Hope, Crawford, Montgomery, Goshen, Wallkill, Wawa- 

 yanda, Chester, Newburgh and Cornwall. 



In the western portion of the county, the formation is represented by 

 interbedded shales, and red, brown or grey sandstones, while in the central 

 part the slates and shales only appear. The sandstone beds again come in 

 towards the northeast. Conglomerates are occasionally seen in the north- 

 eastern part of the county. The slates are black, grey or brown, and often 

 very fissile. The sandstone layers are often several feet in thickness. 



Fossils are rare, but have been found at several localities, notably Sugar 

 Loaf, Rock Tavern, Greycourt and Goshen. They show a mixed Hudson 

 river-Trenton fauna. 



The country underlaid by the Hudson river formation is a fertile one, 

 and the outcrops are comparatively few, forming rounded hills and ridges. 

 These rocks rest unconformably on the Cambrian limestones and gneisses^ and 

 underlie the younger rocks in the same manner. Their thickness in this 

 county is probably not less than 2,000 feet. 



Medina Sandstone. The members of this formation are fine-grained 

 quartzites, conglomerates, shales and sandstones. The formation has its 

 greatest development in Deer Park township, where it forms the western 

 half of Shawangunk mountain. There it consists of a quartzose conglomerate 

 40-50 feet thick, which passes upward into 700 feet of Shawangunk grit. 

 This latter is a hard, evenly bedded quartzite, dipping to the west under the 

 red Medina sandstone, which grades upward into greenish grey shales of the 

 same age. Another area of Medina age forms Pine hill, east of Skunnemunk 

 mountain. Here are 60-70 feet of Oneida conglomerate, dipping to the west 

 over the Cambrian limestones, and passing upward into the Longwood red 

 shales and shaly sandstones, of which there are about seventy feet in 

 Pine hill. 



Their upper members are greenish shales and (piartzites, which crop our 

 south of Cornwall station. They underlie unconformably the Helderberg 

 limestones. 



Helderberg Limestones. There is considerable variation in the distri- 

 bution and thickness of the members of this formation in Orange county. 

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