Stockdale: StyloUtes 



55 



various phases of the phenomenon which have special bear- 

 ing upon the solution theory, in opposition to the pressure 

 theory, follows. 



CONCLUSIVE EVIDENCE WHICH ESTABLISHES THE 

 SOLUTION THEORY OF THE ORIGIN OF STYLO- 

 LITES, AND OPPOSES THE PRESSURE THEORY 



The solution theory and the pressure theory are very 

 strikingly opposed to each other. The first attributes to 

 stylolites an origin in hardened rock; the second, an origin 

 resulting from the differential compression of sediments in 

 the soft, plastic state. Thus, a great amount of the evidence 

 supporting the one theory stands in direct contradiction to 

 the other. With this in view, the writer wishes to present 

 three principal lines of evidence establishing the solution 

 theory; namely: (1) evidence that stylolitic phenomena orig- 

 inate not in plastic rock, but in consolidated, hardened rock, 

 the penetrations of the one stratum fitting into the cavities 

 of the opposite which have been formed by the actual removal 

 (not compression) of rock material; (2) evidence that the 

 clay caps of the penetrations are the solution residue of the 

 dissolved limestone; (3) stratigraphic evidence which pre- 

 cludes the pressure theory and supports the solution theory. 

 The writer believes that proving these points alone is suffi- 

 cient to establish conclusively the solution theory. However, 

 additional evidence along other lines will also be presented. 



1. Evidence that Stylolites Originate in Hardened Rock with 

 the Actual Removal of Rock Material 



Relation of Stylolites to the Lamination of the 

 Rock. The Indiana limestones afford unusual opportunity 

 for a study of the relation of stylolitic structures to sedi- 

 mentary conditions. Field studies of stylolites reveal the 

 conclusive fact that all penetrations bear the same lithologic 

 characteristics as the strata from which they protrude. Es- 

 pecially striking is this observation where a stylolite-seam 

 occurs along a disconformity or a bedding plane between two 

 distinctly lithologically different strata, such as a coarsely fos- 

 silifer ous bed and a fine-grained oolitic, or semi-lithogTaphic 

 one, etc. In such cases, adjacent columns exhibit a sharp con- 

 trast. This observation is yet more striking where a stylolite- 



