92 9 Indiana University Studies 



ated limestone. Chemical analyses show the constituents of 

 the clays to fulfil all the requirements of a residual product 

 of the limestone in which they are found. The insoluble sub- 

 stances exist in the same proportions in both the residual 

 clay and the limestone from which the clay was derived. 



b. The thickness of the clay caps varies in direct propor- 

 tion to the length of the stylolites. 



c. The thickness of the clay caps varies in inverse propor- 

 tion to the purity of the limestone. Stylolites of the purest 

 limestones have the thinnest caps. 



d. There is always a definite relationship between the 

 color of the stylolite-clays and the color of the associated lime- 

 stone. 



e. Corroded fossil fragments are found in the clay caps. 



3. Certain geologic and stratigraphic relations suggest 

 evidence which precludes all theories but the solution theory. 

 The most important are : 



a. The occurrence of stylolitic phenomena is limited to 

 carbonate rocks — rocks which are soluble. 



h. The pressure theory explains the clay partings as orig- 

 inal deposits of clay laid down in due order with the other 

 sediments. Therefore the direction of stylolite-seams would 

 of necessity be parallel with the stratification of the rock. 

 Field observations show numerous examples of stylolite-part- 

 ings cutting across the lamination at various angles — in some 

 cases at right angles. 



c. Branching stylolite-seams are common. 



d. Stylolites occur along disconformities between geologic 

 formations. 



4. Other evidence in support of the solution theory fol- 

 lows : 



a. Various deposits of mineral matter are associated with 

 stylolitic phenomena. They result from a supersaturation of 

 the ground waters as a result of increased solution at the ends 

 of the columns where the pressure is greatest. 



h. The origin of stylolites is somewhat analogous to that 

 of the solution type of impressed pebbles. - 



