DIAGENESIS: ENTEROLITHIC STRUCTURE 759 



be the case in tectonic or in gliding deformations. Thus deforma- 

 tion is shown in whichever direction the section of the formation is 

 cut, nor is there any evidence of sHckensiding, such as is to be 

 expected if the deformation is tectonic. 



Koken, who described the disturbed layers of the Upper Mus- 

 clielkalk of the Neckar A^alley in detail, and originated the name 

 Gckrosckalk for them, held that the folding and wrinkling were due 

 to vertical pressure of overlying rocks upon the still plastic layers. 

 He notes, however, that the folds are notably sharp and their limbs 

 are thickened as is the case in deformations formed by swelling 



Myo pTioria Gpjdfussi 



caoio 



Fig. 161. Enterolithic structure in the Upper Muschelkalk (Gekrosekalk) of 

 the Neckar Valley in Wiirttemberg, Germany. (After Koken.) 



masses, such as gypsum, but not through horizontal pressure. While 

 it is not difficult to conceive that mere vertical pressure on still 

 plastic layers can produce deformation of these layers, it is not 

 quite clear what should cause the retention of plasticity in some 

 layers and not in others. The deformed Muschelkalk layers are 

 bluish, argillaceous calcilutytes, much like the similarly deformed 

 layers of the Niagara section. In both cases internal pressure due 

 to crystallization seems to have been an active agent in the deforma- 

 tion of the rock. 



III. DoLOMITIZATION OF LlMESTONi:S. 



The change of limestones itito dolomites, or dolomitization, has 

 occurred in all geologic ages and is in progress to-day. (Pfafif-26.) 



