National Geographic : 1894 May 23
82 Hayes and Campbell-Appalachian Geomorphology. axes of post-Cretaceous oscillation have also been lines of Paleo zoic movement. A second and more clearly defined axis of elevation, 0 P, is found crossing the province in the vicinity of Chattanooga. Its trend is nearly due north and south, and it has been traced nearly as far north as Cincinnati. If the axis be continued across the Ohio river it falls in line with the eastern branch of the Cincin nati arch passing through Findlay and Toledo, Ohio. This also may be only a coincidence, but it strongly suggests genetic con nection between the portions of the axis north and south of Cincinnati. The third and most prominent of the transverse axes crosses the southern portion of the province, passing near Atlanta and forming a tangent to the great northwestward bend of the Ten nessee river. It was first recognized by McGee in studying the sediments of the southern Atlantic coastal plain and Mississippi embayment. He describes this "Charleston-Memphis axis "* as an axis of maximum subsidence during both low level periods (represented by the Lafayette and Columbia formations) and an axis of maximum uplift during both high level periods. It is represented on the map by the broken line A B, having a nearly east-and-west direction; it intersects the last described north and-south transverse axis as well as the longitudinal axes, and since, as shown by the contours, it is at present a line of depres sion the effect of the elevation along the other axes is wholly or partially neutralized at their intersections. The oscillations on this axis A B have been an important factor in determin ing the drainage of this region and will be again referred to in the second part of this paper. The probability of orogenic forces having been active upon the transverse axes during Paleozoic time was mentioned above. In case of the axis A B, there is proof of such activity at two or more distinct epochs. In mapping the Paleozoic formations of northern Georgia and Alabama it was found that two terranes which present strong indications of having been deposited under shore conditions terminate abruptly against this line. These shore formations are the Birmingham breccia at the top of the Knox dolomite and the Oxmoor sandstone occurring in the lower Carboniferous. Other stratigraphic changes scarcely less * The Gulf of Mexico as a Measure of Isostacy (abstract), byW J McGee: Bull. Geol. Soc. Am., vol. iii, p. 503.
1894 Jun 22
1894 Apr 25