1922] Geology of the ]\Iuscle Shoals Area, Alabama 89 



because of this threatened leakage that the writer was asked to make 

 a geological report to the Government concerning the dam founda- 

 tion during the war period. 



Although there is a considerable area of the Tuscumbia which 

 will be flooded by the Wilson dam, the trend of the rocks is such 

 that no great danger from leakage is to be expected except in the 

 area near the dam, where considerable pressure grouting will be 

 necessary. 



The proposed Dam No. 3 is to be located near the head of the 

 Big Muscle Shoals. At this point the Lauderdale chert occupies the 

 southern bluff while a shale and a very soluble crinoidal limestone, 

 lying below the Lauderdale chert, occupy the northern portion of 

 the stream bed and the northern bluff. At this locality the northern 

 end of the proposed dam is the weak one and the weakness is of 

 greater concern than at the south end of the Wilson Dam. 



The strata throughout the area show a number of small, rather 

 sharp folds. These run nearly with the strike. One such fold is 

 seen in the bed of the stream near the north end of the Wilson Dam. 

 It does not here constitute a line of weakness. Another such sharp 

 fold cuts diagonally across the river at Bainbridge Eddy, here bring- 

 ing up the less resistant shale and limestone which have yielded the 

 deep and narrow channel. 



The upper Lauderdale in places contains small cavities containing 

 oil residues. That gas is also present, in small amounts at least, is 

 also demonstrated by the secondary explosions which were so com- 

 mon following blasts made at the location of the new power plant on 

 the south side of the river below the Wilson Dam. 



Chapel Hill," N. C. 



