STKATIGRAPHIC CLASSIFICATION DIASTKOPHIC CRITERIA 415 



part. The typical Bays is succeedod by sliales and sandstones evidently 

 of Cincinnatian age. If correctly determined the succession in Bays 

 Mountain suggests an hiatus between the Bays sandstone and the suc- 

 ceeding formation corresponding to at least the middle and upper Tren- 

 ton. West of Bays Mountain, as in Clinch Mountain, the Moccasin is 

 succeeded by a great series of shaly limestone and calcareous shale, 

 mapped as '^Sevier shale," the lower part of which, according to its fos- 

 sils, is of Trenton age. Farther west, in the Clinton trough, the equiva- 

 lent Trenton deposits are limestone, and hence were referred by the 

 geologists who mapped this area to the Chickamauga limestone. During 

 the greater part of the Trenton, therefore, the Athens trough seems to 

 have been emerged and the sea confined to the west of Bays Mountain. 

 The Eden sea, however, spread farther eastward, as did also the red cal- 

 careous sandstone which succeeds it. The latter follows the great valley 

 from northern Alabama to southern Pennsylvania. It is of late middle 

 (Fairview) Cincinnatian (excluding the Eichmond) age. In Pennsyl- 

 vania it has been incorrectly referred to the Juniata sandstone, which is 

 a more westerly and younger formation. In northern Virginia it con- 

 stitutes the lower part of the Massanutten sandstone. On maps of south- 

 western Virginia and eastern Tennessee, published by the U. S. Geologi- 

 cal Survey, it is referred to, apparently erroneously, as Bays sandstone. 



According to the foregoing brief account, the Ordovician part of which 

 is graphically illustrated on page 544, it appears that, beginning with the 

 Copper Eidge chert and ending with the last of the Ordovician stages, 

 the attitude of the Appalachian Valley troughs in east Tennessee was 

 modified many times by differential vertical movements and the distribu- 

 tion of the successive formations correspondingly changed. Similar and 

 perhaps even more striking oscillations occurred in central Alabama. 



Oscillations of the Adirondack uplift. — Equally convincing evidence 

 of local differential movement of the lithosphere is brought out by 

 comparing the sections of Ordovician and earlier rocks on the east and 

 west sides of the Adirondack uplift. Thus, while the lower beds of the 

 Beekmantown occur on both sides, the later deposits of this series are 

 found only on the eastern side in the Champlain Valley. Non-deposi- 

 tion continued on the western side, while the lower and middle divisions 

 of the Chazy were being laid down on the east side. Then the area of 

 deposition was shifted to the west side, where the upper Stones Eiver, or 

 Pamelia, limestone is found resting on beds of early Beekmantown age. 

 No deposits corresponding to the Pamelia are found in the Champlain 

 Valley, where the upper Chazy, which, on the other hand, is wanting on 

 the west side, rests on the slightly eroded middle Chazy. The succeed- 



