6o2 



WILLIAM J. MILLER 



it developed unsymmetrical waves or ripples in its mass." After 

 the mass came to rest more lime mud was deposited upon its surface. 

 Since then the whole has been solidified. The contorted zone shows 

 notable variations in thickness from a few inches to several feet 

 (Fig. 7). Certain criteria which seem to rather dej&nitely place 

 this occurrence in the category of subaqueous gliding, and which 

 particularly distinguish it from the above-described examples 

 beheved to have resulted from differential movements after deposi- 

 tion of the overlying layers, are the following: (i) the notable 

 variations in thickness of the contorted zone locally, even within a 

 few feet; (2) the very irregular upper surface of the folded zone, 



Fig. 7. — Folded limestone and limestone-conglomerate, several feet thick, between 

 non-folded beds near BeUefonte, Pennsylvania. (After T. C. Brown.) 



and the rather regular under surface; (3) the bulging of the immedi- 

 ately overlying strata over the little anticlinal folds; and (4) the 

 distinct evidence of the filling of the depressions on the upper surface 

 of the corrugated zone before the general layers of overlying ma- 

 terials were laid down. 



D. W. Johnson has kindly allowed me to reproduce a picture 

 (Fig. 8) of a moderately corrugated zone within the cross-bedded Tri- 

 assic red beds near Kanab, Utah. Regarding the occurrence he says : 



The crumpling and faulting must have taken place during the process of 

 deposition, for the erosion plane beveling the deposit a few inches above the 

 corrugations, and upon which the next layer of cross-bedded sand was deposited, 

 shows no disturbance. I have therefore attributed the corrugations and 

 miniature faults to slumping or settling of the deposit as it was built forward, 

 delta-like, under the influence of current action.^ 



^ Personal communication from Professor Johnson. 



