2o6 Bulletin of Laboratories of Denison University [Voi. xii 



west of a line drawn northeastward through Cartcrsville marks 

 a rather smooth plain, etched out of the soft shales and lime- 

 stone of Cambrian age. Its average elevation above mean sea- 

 level is between 800 and 900 ft. Slight inequalities in the form 

 of irregular hills or minor ridges, rising from 100 to 125 ft. 

 above the general surface of the plain, denote unreduced areas. 

 Elevations of less than 800 ft. — from 750 to 775 ft. — are re- 

 corded in places along some of the larger stream-courses. West- 

 ward, the plain grades into the Knox dolomite plateau, a slight- 

 ly more resistant magnesian limestone, whose general average 

 elevation is but little above that of the Cartersville portion of 

 the Paleozoic plain. 



Beginning with, and including, the long central band of 

 Weisner quartzite, that part of the mapped area to the south of 

 the Etowah river and east of the plain already defined, is a sec- 

 ond area whose surface is higher than that of the Paleozoic 

 plain described and in marked contrast to it. The larger por- 

 tion of this area forms the northwestward extension of the 

 Piedmont plateau. Its general surface-elevation will average 

 less than 1,000 ft. above mean sea-level, with numerous resid- 

 uals in the form of irregular hills and ridges standing several 

 hundred feet above the plateau surface. The surface then is an 

 irregular one, trenched by comparatively deep and narrow 

 stream-channels, in many places cut through the thick covering 

 of decayed rock into the hard rock beneath. The northeast 

 corner of the mapped area forms the equivalent lowering por- 

 tion of the Appalachians, showing elevations of from 1,800 to 

 2,000 ft. This marks the roughest surface in the district. The 

 higher and more roughened surface of the eastern half of the 

 mapped area is etched out of geologically old, highly-tilted and 

 disturbed metamorphic crystalline rocks, whose age for the most 

 part is pre-Cambrian. 



The entire district covered by the map is well watered. Its 

 drainage is through numerous nearly north- and south-flowing 

 streams tributary to the Etowah river, the master stream of the 

 region, which has a general westward course, passing within a 

 short distance south of the town of Cartersville. 



