INTRAFORMATIONAL CORRUGATED ROCKS 



603 



In view of the fact of the very moderate degree of corrugation, 

 a slight amount of subaqueous slumping or forward settling, per- 

 haps under earthquake impetus, would have produced the struc- 

 tures. There may have been no actual gliding over the lower 

 erosion surface at all. Erosion intervals, under the conditions 

 of shifting currents during the deposition of the cross-bedded 

 sandstones, would be expected. The corrugations of the disturbed 

 zone might possibly have resulted from slight differential sHpping 



Fig. 8. — Intraformational cross-bedded, corrugated, Triassic sandstone near 

 Kanab, Utah. (After D, W. Johnson.) 



along the erosion surfaces but, in spite of certain outward resem- 

 blances to the intercalated contorted zones above described as due 

 to differential movement after deposition of the immediatley over- 

 lying beds, the writer believes that the structures in the Kanab 

 occurrence are essentially different, and that they are correctly 

 interpreted by Johnson. 



Norton^ has discussed subaqueous gliding as a cause of a certain 

 type of breccias, but examples certainly coming under this category 

 are apparently not common. 



^ W. H. Norton, Jour. Geol., Vol. XXV (1917), pp. 182-85. 



