Stockdale: Stylolites 



89 



been known, and gave rise to the early suggestions of the 

 crystahization theory (see p. 22). The occurrence of calcite, 

 gypsum, magnesium sulfate, and strontium sulfate has been 

 described by various writers. Deposits of calcite, with often 

 a subordinate amount of pyrite, are the principal ones found 

 in connection with Indiana stylolites. Coatings of calcite on 

 the sides of the columns occur sometimes with a thickness 

 of as much as 1/16 of an inch or more. The deposits are 

 thicker, in many cases, nearer the end (the older part) than 

 the base of a column. Such deposits have usually been slicken- 

 sided by further growth and interpenetration. This feature 

 is unexplained by all other theories. Since the sides of stylo- 

 lites are free from pressure, the deposition of mineral mat- 

 ter there is to be expected. 



Several examples are found where small joints in the 

 stratum immediately underlying a stylolite-seam are infil- 

 trated with calcite. This mineral matter was no doubt de- 

 rived from the solution of the limestone along the stylolite- 

 parting. Fractures on the convex side of curved stylolites 

 are often filled with mineral m.atter. Wagner stresses this 

 observation (Wagner, 1913, p. 118). Various minor evi- 

 dences of the deposition of mineral matter in connection with 

 stylolites are common. 



Analogy of the Origin of Stylolites to that of Im- 

 pressed Pebbles. The occurrence of the phenomenon of im- 

 pressed pebbles (of the solution type — see p. 16) is in itself 

 evidence in support of the solution theory of stylolites. In 

 both phenomena — impressed pebbles and stylolites — the solu- 

 tion of the one part results at the point of pressure of the 

 other. Rothpletz's observation of two impressed limestone 

 pebbles whose contact was marked by a minute stylolite-suture 

 (see p. 18, and Figs. 9 and 10) is an observation in direct sup- 

 port of the solution theory of the origin of stylolites. Here 

 was a case of an impression in a pebble resulting from the 

 actual removal of hardened rock material by solution, where 

 the contact with the pressed-in pebble was slightly inter- 

 teethed as a result of subordinate differential solution, 



CONCLUSION 



The abundance of evidence in support of the solution the- 

 ory of the origin of stylolites establishes the conclusion that 



