162 



STRUCTURAL GEOLOGY OF NORTH AMERICA 



TACONIC RANGE EAST OF TROY 



GREEN MTS. 



TACONIC RANGE NEAR CHATHAM 



Chatham 

 thrust 



HUDSON HIGHLAND 



p€g 



EAST OF POUGHKEEPSIE 

 Ohr 



HOUS ATONIC 

 Ohr 



HIGHLAND 

 p€g 



Fig. 11.9. Cross sections of central and southern Taconic Range. Section east of Troy, N. Y., after 

 Balk, 1953. p€g, Precambrian gneiss; Cc, Lower Cambrian Cheshire quartzite; CO, Cambro-Ordo- 

 vician limestone and dolomite; Oa, gray, purple, and black slate and quartz-chlorite schist. 



Section near Chatham, N. Y., after Craddock, 1957. €s, green slate with interbedded gray- 



wacke and quartzite; Oc, carbonate rock; Ode, green shale; Ons, red shale member; Onm, 

 Mount Merino dark shale wtih interbedded chert; Ona, Austin Glen graywacke and dark shale. 

 Section east of Poughkeepsie, N. Y., after Balk, 1937; pCg, Precambrian gneiss; €Ow, 

 Wappinger dolomitic limestone; Ohr, Hudson River pel lite, phyllite, and schist. 



the southern core is believed by Cady ( 1945 ) to be part of the Taconic 

 allochthone. See map of Fig. 11.10. In its east flank the Green Mountain 

 anticlinorium contains a discontinuous belt of ultrabasic intrusives which 

 are associated with volcanics including pillow basalt. 



Taconic Mountains 



The Taconic Mountains are a low range of hills composed mostly of 

 argillaceous rocks such as phyllite, slate, and shale. This clastic sequence 

 is surrounded in the adjacent lowlands by rocks, chiefly carbonates. In the 

 Taconic sequence, as it is called, there is one thin quartzite formation 

 and one very thin limestone which together form perhaps 5 percent 

 of the section. There are three slate formations of Middle Ordovician age 



and six of Lower Cambrian. No Middle or Upper Cambrian is present 

 and no Lower Ordovician. The Lower Cambrian of the Taconic Range 

 lies beside the Lower Cambrian of the valleys and the two groups have 

 no features in common except that of age (Keith, in Longwell, 1933). 

 Similarly, most of the Ordovician of the mountains differs from the Ordo- 

 vician of the surrounding valleys. These relations have led through a long 

 controversy to the interpretation of the Taconic clastic sequence as a 

 klippe, which represents an eastern trough facies that has been thrust 

 westward 30 to 50 miles or more on a western trough sequence. It is part 

 of the Taconic allochthone. The carbonates of the western trough sup- 

 posedly are the autochthone. See cross section D-D', Fig. 11.11. The 

 details and relations will be taken up later. 



