GEOLOGIC FORMATIONS OF NEW YORK 143 



Middle Cambrian, or Acadian. 



The type rocks are the shales and slates of New Brunswick, 

 Newfoundland and Braintree, Mass., and correlated with them 

 are some limestones in Dutchess county. The characteristic fos- 

 sils are the Paradoxides trilobites. 



Lower Cambrian, or Georgian. 



The type rocks are slates, limestones and the ' red sandrock ' of 

 western Vermont; and correlated with them the shales and in- 

 terbedded limestones and roofing slates of Washington and Rens- 

 selaer counties. The characteristic fossils are the Olenellus trilo- 

 bites. 



Georgian 



The lowest rock is a bedded quartzite, resting upon the Arch- 

 aean. This is seen on the flank of Stissing mountain, and be- 

 tween Fishkill and Poughquag, in Dutchess county. From here 

 its outcrops extend northeasterly through Massachusetts and 

 Vermont, where it attains a great thickness. 



At Stissing mountain it passes above into a limestone contain- 

 ing Lower Cambrian fossils. Above this lies a considerable 

 thickness of arenaceous limestone, frequently passing into cal- 

 careous shale, and containing Middle Cambrian fossils. 



Near Poughkeepsie an extensive limestone formation contains 

 Upper Cambrian fossils. 



Northward, in Washington county, the quartzite is represented 

 by a great thickness of shales, slates, sandstones and limestones, 

 well shown along a line between Greenwich and Salem, and the 

 superjacent limestones of Dutchess county are entirely replaced 

 in both Rensselaer and Washington counties by slates, shales and 

 sandstones. Mingled fossils of Lower and Middle Cambrian are 

 found at Berlin, Rensselaer county. These formations continue 

 northeastward into Canada. 



The great belt of roofing slate in western Vermont and Wash- 

 ington county, belongs to this (Georgian) group. The greatest 

 development of this formation is at Georgia, Vt, from which 

 place it extends southward into Washington county, where it 



