GEOLOGY OF THE MUSCLE SHOALS AREA, ALABAMA 

 By W. F. Prouty 



The Tennessee River at its confluence with the Ohio is the larger 

 of the two streams. The Tennessee represents, about as perfectly as 

 any stream known, a shift of course through successive river cap- 

 ture. Rejuvenation has caused the down-cutting of the Tennessee 

 into its old peneplain. In the neighborhood of Florence, Alabama, 

 where the stream makes a considerable bend toward the north, the 

 older and more resistant rocks of the Nashville arch outcrop and 

 cause the Muscle Shoals, which have a fall of more than 140 feet 

 in the course of a fcAv miles. In the Waldron Ridge the lower part 

 of the Pennsylvanian and upper part of the Mississippian rocks are 

 well exposed. In the Muscle Shoals area proper the lower portion 

 of Mississippian is alone seen along the stream. 



In this portion of the State the Fort Payne series is composed of 

 the Tuscumbia limestone above and the Lauderdale chert, limestone 

 and shale below. The very resistant Lauderdale chert forms the 

 bed of the stream throughout the area of the shoals. This rock dips 

 more steeply than the stream so that in going from the head to the 

 foot of the shoals one passes from the bottom to the top of the heavy 

 Lauderdale chert beds. As these beds are jointed, they break off into 

 steps which form the riffles across the stream, usually at a considerable 

 angle to the flow of the stream. 



The big or Wilson dam, now under construction, is located near 

 the foot of the shoals and near the top of the Lauderdale chert. At 

 this locality the river runs south of Avest, the 4000 foot dam runs 

 a little west of north and the dip of the formations is practically due 

 south. At this point the dip is unusually large, being about 60 feet 

 for the width of the river. As a result of this the bed of the stream 

 and the north bluff are composed entirely of the Lauderdale chert 

 formation while the bluff at the south end of the dam is made up 

 in part of the less resistant chert of the Lauderdale, and at higher 

 levels of the more soluble limestone of the Tuscumbia formation. It 

 is in the portion of the proposed flooded area occupied by this more 

 soluble limestone that trouble from leakage is anticipated and it was 



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