100 



STRUCTURAL GEOLOGY OF NORTH AMERICA 



TIME SCALE 



CENTRAL 

 PENNSYLVANIA 



SUSQUE- 

 HANNA- 

 NEW RIVER 



NEW RIVER- 

 TENNESSEE 



TENNESSEE- 

 ALABAMA 



z 

 < 

 a 

 < 

 z 

 < 

 u 





LARKE 



BEEKMAN- 

 T0WN 



CHEPULTEPEC 



CHEPULTEPEC 



z 



4 



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 ■ 



2 



< 



O 



tt 

 in 

 <L 



a. 



3 



MADISON 

 TREMPEALEAU 



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 a 

 r*- 



o 

 o 



IS 



(9 



IE 



a> 

 ■a 



ui 



4 

 (9 



MINES 

 150-200 



ORE HILL 

 STACY 



C0N0C0- 

 CHEAGUE 

 1600-2000 



COPPER RIDGE 

 1200-2800 



COPPER RIDGE 

 1200-2800 



BIBB 



250-500 

 KETONA 



400-600 

 BRIERFIELD 



1500 





FRANCONIA 



DRESBACH 



WARRIOR 

 1250 



NOLICHUCKY 

 400-750+ 



4 

 O 



Z> 

 4 



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4 

 Z 

 O 



o 



NOLICHUCKY 



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00 



2 



4 

 U 



M 



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 o 



a 



z 



MARJUM 





ELBROOK 

 1800-3000 



K 

 HI 

 3£ 



4 

 Z 

 O 



X 



MARYVILLE 

 150-750 



MARYVILLE 



WHEELER 



PLEASANT HILL 

 600 



ROGERSVILLE 

 70-250 



ROGERSVILLE 



SWASEY 



DOME 





RUTLEDCE 

 200-500 



RUTLEDGE 



OPHIR 



HOWELL 











Fig. 8.3. Middle and Upper Cambrian formations of central and southern Appalachians. After 

 Resser, 1938. 



The Mississippian trough coincides with the Valley and Ridge province 

 and does not reflect the great westward bulging wedges of the Ordovician 

 and Devonian. See Plate 6. It is probable that the Mississippian seas 

 shored at about the Rlue Ridge. 



Mississippian rocks may never have been deposited in the northern 

 part of the geosyncline in southeastern and eastern New York. The 

 coarsest beds in eastern Pennsylvania were deposited nearest the high- 



lands that formed in New England in the Devonian, and with reduction 

 of the highlands the earlier Mississippian elastics were succeeded by 

 calcareous sediments (Kay, 1942). 



Pennsylvanian Clastics. The Pennsylvanian strata are distinctly clastic, 

 both in the shelf and the geosynclinal areas. They are the great coal- 

 bearing formations of the Allegheny Plateaus and Valley and Ridge 

 provinces. A cross section from Virginia to Illinois that does not contain 

 the present structural details is shown in Fig. 8.10. The trough is deep- 

 est in Alabama, where a maximum of 10,000 feet of strata — all Pottsville 

 — is known. The Pottsville thins gradually northeastward until in Pennsyl- 

 vania it is only 200 to 400 feet thick. As the Pottsville thins, younger 

 Pennsylvanian formations appear, and in West Virginia and Pennsylvania 

 the Allegheny formation is 300 feet thick, the Conemaugh 600 feet, and 

 the Monongahela with the extremely valuable Pittsburgh coal at the base, 

 250 feet. The maximum thickness of the Upper Pennsylvanian is estimated 

 to be 3000 feet. 



The 10,000 feet of Pottsville beds in Alabama in the Coosa coal field 

 area is rather restricted in east-west distribution because of the nearness 

 of the Nashville arch to the Blue Ridge, but probably the original dis- 

 tribution was in the form of a wedge which spread westward over the 

 site of the arch. This is the representation of King, 1959. 



Permian System. Overlying the Monongahela formation in an oval 

 area in West Virginia and Ohio, entirely in the Plateau province, is the 

 Dunkard group or "upper barren measures" of Permian age. It is com- 

 posed of shale, partly red, and sandstone with thin coal beds. Its maxi- 

 mum thickness is about 1500 feet. 



FOLDED AND THRUST-FAULTED APPALACHIAN MOUNTAINS 



Salients and Recesses 



When viewed as a whole, the folded and thrust-faulted belt of the 

 central and southern Appalachians consists of two major salients and 

 three recesses. These are terms used by Keith (1923) in his well-known 

 "Outlines of Appalachian structure." The salients are the arclike portions 

 of the belt that are convex inland, and the recesses are the arclike portions 



