INTRAFORMATIONAL CORRUGATED ROCKS 6oi 



It is to be noted that Nason's explanation clearly involves the 

 principle of differential movement which is advocated by the 

 present writer as the cause of most intraformational contorted clay 

 beds. 



SUBAQUEOUS GLIDING OR SLUMPING 



The hypothesis of subaqueous gliding has been elaborated by 

 Hahn^ who has considered most cases of intraformational contorted 

 strata to belong in that category. According to Hahn's hypothesis 

 a lenslike mass breaking loose from any cause (e.g., earthquake 

 shock) would glide down a subaqueous slope and, because of the 

 striking of some obstacle on the bottom and increased friction and 

 water pressure, the gliding mass would come to rest only after it had 

 become considerably deformed or contorted. Sediments would then 

 be deposited in normal order on top of the crumpled layer. The 

 most intense folding would be toward the front of the transposed 

 mass, and of course the strike of the folds would be at right angles 

 to the direction of the moving mass. Conditions for such gUding 

 are regarded as favorable at many places on the marginal sea bottom. 



In the paper above cited, Hahn especially refers to the intra- 

 formational contorted zones at Trenton Falls, New York, as typical 

 examples of submarine slumping among ancient strata. In a 

 paper already published the writer has given reasons for believing 

 that Hahn's hypothesis cannot possibly account for the Trenton 

 Falls occurrences.^ Hahn has regarded most cases of intercalated 

 corrugated strata as results of subaqueous ghding, while the present 

 writer regards most of them by far as results of differential move- 

 ments within the masses of strata. 



T. C. Brown^ has described what appears to be a clear case of 

 intraformational folding in Paleozoic strata near Belief on te, Penn- 

 sylvania. In regard to this occurrence Brown says in part: "At 

 periodic intervals these beds of calcareous mud and uitermmgled 

 pebbles slumped or slid along the bottom under the influence of 

 gravity. At the time of the slump or sHde the matrix around the 

 pebbles consisted of incoherent lime mud or paste. As it moved 



' F. Hahn, Neiies Jahrh. Beil., Vol. XXXVI (1915), PP- 1-41. 

 => W. J. Miller, N.V. State Miis. Bull. 177 (iQis)? PP- i4o-43- 

 3 T. C. Brown, Jour. Geol., Vol. XXI (1913), pp. 241-43. 



