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Indiana University Studies 



amples, observed by the writer, is that of a stromatoporoid 

 into which a series of columns of considerable size have pene- 

 trated (see Fig. 31). Here is a conclusive case of part of the 

 fossil structure having been actually removed, and occupied 

 by the upward-pointing columns of the rock below. The 

 residual clay is found in its place at the end of the columns. 



These numerous, partially cut fossil shells, mineral grains, 

 etc., mentioned above, show no evidence of compression or 

 disturbance from their original positions. They have been 

 cut after the rock material was firmly hardened and cemented 

 together. These observations alone preclude all other theories 

 of the origin of stylolites. 



Penetration of One Stylolite-Seam by Another Ad- 

 jacent Parallel Seam. The vertical distance between 

 stylolite-seams is quite variable. It is sometimes as small as a 

 few inches. Sometimes the seams are so close as to touch, 

 penetrate, or pierce one another. In all cases, parallel stylo- 

 lite-seams, as they grow, become closer together by a distance 

 dependent upon the amount of solution which takes place. 

 Thus, two parallel seams, which in their beginning were sepa- 

 rated by a very thin layer, might, after sufficient solution and 

 growth, become so close as to touch one another (see Fig. 32). 

 Continued solution would result in the interpenetration of the 

 two, and still further growth would cause a partial, or com- 

 plete, eradication of one or the other. These various stages 

 are observed in the Indiana limestones. The above-mentioned 

 Fig. 25 is an example where a large, major stylolite-seam has 

 partially destroyed a small, minor one. Individual stylolite- 

 columns of various sizes, which bear a partially penetrated 

 column of an overlying or underlying seam, have been ob- 

 served. Wagner (1913, p. 118) cites the example of an older 

 curved stylolite which has been pierced by a younger vertical 

 one (see Fig. 33). All this evidence is decisive proof of the 

 actual removal of rock material, and presents a phase of the 

 problem which can be explained by no other theory than 

 solution. 



Striated and Slickensided Faces of Stylolites. The 

 ever-present striations on the side-surfaces of stylolites, run- 

 ning parallel with the direction of penetration, present a 

 problem hard to explain by the pressure, and other theories. 



