REPORT OF THE DIRECTOR I914 



139 



Fig. 3. Diagram illustrating Hahn's hypothesis of submarine slumping 



A lenslike mass breaking loose from any cause (for example, earth- 

 quake shock) would glide down the submarine slope and, because 

 of increased friction and water pressure and the striking of some 

 obstacle on the sea bottom, the gliding mass would come to rest 

 only after it had become considerably deformed or contorted, as 

 shown in the diagram. Sediments would then be deposited in 

 normal order over 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 move- 

 ment of the sliding mass. Conditions for such submarine gliding are 

 regarded as favorable at many places along the marginal sea bottom. 

 Some of the points supporting this submarine sliding hypothesis, 

 according to Hahn, are as follows : 



1 Observed production of contortions by subaqueous gliding, 

 for example, that in Lake Zurich 1875. 



2 Various portions of the sea bottom are known to have slopes 

 of from 4 to 18 degrees or more which would be sufficiently steep 

 for masses to slide down under certain conditions. 



3 The texture (character) of materials within the contorted zones 

 is essentially the same as that of the underlying and overlying ma- 

 terials, and hence the disturbed zones were not horizons of weakness 

 which were distorted under pressure. 



4 The analogy of the Trenton Falls contorted zones wuth those 

 of certain other regions. 



5 Tectonic contortions are pressure phenomena produced under 

 heavy loads. 



6 The corrugated zones are not of tectonic origin, that is, due 

 to differential movements within the Trenton limestone because 

 of (a) absence of stretched or flattened out masses; (b) absence 

 of distinct slickensided or streaked surfaces; and (c) absence of 

 fragments of both the underlying and overlying masses within the 

 disturbed zones. 



