Stockdale: Stylolites 



27 



shale, which, when later broken up, comes to rest as the clay 

 caps at the ends of the stylolites. (5) The longer columns 

 usually have the convex side of the shell uppermost; and the 

 shorter ones, the reverse. When the shell lies obliquely on 

 the column, the latter will, in most cases, be found curved, 

 the degree of obliquity of the shell determining the amount 

 of curvature. 



Experiment of Gilmbel. Believing, as did Quenstedt and 

 Marsh, that stylolites are due to differential compression of 

 sediments before consolidation, Giimbel (1882, p. 642) tried 

 to prove his theory experimentally. In his explanation of 

 stylolites, he placed the emphasis on the always-present clay 

 cap at the ends of the columns. He suggested that they are 

 always formed at the horizon of a clay or marl layer between 

 two lime layers. By the drying out of this clay, cracks would 

 be formed, and the layer would be broken up. Pressure of 

 the above, yet-plastic, lime ooze would force a portion of the 

 broken clay parts to settle down into the underlying bed of 

 plastic sediment, while another portion would be projected 

 into the overlying bed. 



In his experiment, Gtimbel took a mass of plastic ooze, 

 covered by a thin layer of clay, and placed over this a metal 

 plate in which various shaped holes had been cut. Exertion 

 of pressure upon this plate resulted in columns of the under- 

 lying plastic substance being pushed up thru the artificial 

 holes of the plate. Continuing his experiment to prove his 

 theory, Giimbel repeated the conditions; but, before exerting 

 the pressure, covered the plate with another layer of plastic 

 material. Upon application of pressure, columns of the mass 

 below the plate were forced up into the overlying mass, and 

 thus the figure of stylolites resulted. 



Giimbel's experiment met strenuous objections from Roth- 

 pletz, Fuchs, Reis, and Wagner, who conclusively pointed out 

 that it was insufficient to explain the origin of stylolites. 

 Rothpletz showed that the physical basis of the experiment 

 w^s not sound; that the clay cap took a role which it could 

 not possibly play; that the clay layer, instead of being torn 

 apart, would be compressed together by the weight of the 

 superimposed layer. Giimbel's experiment and theory failed 

 to explain the occurrence of horizontal stylolites and other 

 complexities. 



5—22663 



