C. H. Hitchcock — Crystalline Rocks of Alabama. 281 



plain, at the head of navigation for large steamboats. A return 

 trip northward near the State line enabled us to correct and 

 confirm the impressions derived from the study of the section. 



Certain obvious conclusions may be briefly summarized. 

 First as to structure: (a) The contact between the Silurian 

 limestones and the Ocoee group is not the natural one. There 

 is no deep cut like that across the Blue Eidge at the James 

 River to show the two groups in their undisturbed primal 

 position, (b) The Ocoee slates dips are small, and when pro- 

 tracted upon a scale there seem to be an inverted anticlinal in 

 the Syllacauga section. This* position is due to the tangential 

 motion of the elevating force and there is no reason to doubt 

 Safford's assignment of these slates to the horizon suggested by 

 the geographical position, —between the Potsdam and the 

 ancient gneiss, (c) The first mica schist or gneissic band, as in 

 so many sections farther north is an inverted anticlinal with 

 many subordinate folds. As a careful study of this group at 

 the north develops unexpected normal anticlinals, so it will 

 probably be the case in the south, (d) Belts of chloritic and 

 argillaceous schists, when conforming to the adjacent mono- 

 clinal gneisses or coarsely crystalline mica schists, are supposed 

 to indicate compressed folded synclinals. Hence besides the 

 western anticlinal between the Ocoee range and Ashland there 

 must be at least one inverted synclinal of the chloritic schists 

 if not others in the older group, (e) The second or argillaceous 

 belt is synclinal in attitude and so are the underlying gneisses, 

 between Ashland and Alexander City. It may be convenient 

 to term the chloritic belt the Lower and the argillaceous belt 

 the Upper Huronian. (/) Dadeville, in the midst of the indis- 

 putable Laurentians, is the center of a very large synclinal. 



Second, as to mineral resemblances: (a) No one will hesitate 

 to accept the identity of the limestones and quartzite in the 

 edge of the great Appalachian valley with the corresponding- 

 rocks in Virginia and New England known as the Lower 

 Silurian and Potsdam sandstone, (b) The Ocoee corresponds 

 best with the later Huronian or the earlier Cambrian of the 

 north. There is no good reason for calling it Acadian, (c) A 

 section across northern New England has many points of 

 resemblance to the one in Alabama described above. In 

 northern Vermont after leaving the Potsdam there is a band of 

 argillitic schists very like the Ocoee. This lies west of the 

 Green Mountains and by Zadock Thompson in an unpublished 

 map was once called the Magnesian slate of the Taconic system. 

 The Green Mountain gneissic anticlinal follows with a repeti- 

 tion of the Ocoee-like slates and also the heavy chloritic group 

 with serpentines referred to the Huronian by most authors. 



Am. Jour. Sci.— Third Series, Vol. XXX, No. 178, Oct., 1885. 

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