Stockdale: Stylolites 



• 91 



1. Stylolites originate in hardened, and not plastic rock, 

 with the actual removal of rock material. They do not result 

 from a differential compression of soft sediment. Evidence 

 in support of this : 



a. The laminae of stylolites are sharply cut off at the 

 edges of each column. There is no evidence of disturbance or 

 compression of the lamination of the columns, or of the rock 

 above and below the columns. 



b. Small, once-continuous stylolite-seams appearing across 

 every other column of a major stylolite-suture are found. The 

 missing portions of the once-continuous, minor parting have 

 been actually removed by the penetration of the larger col- 

 umns of the major seam. 



c. A slight sagging of stylolite-seams, equivalent to the 

 amount of penetration of the columns, is occasionally ob- 

 served. 



d. Stylolites have the exact lithologic characteristics, and 

 color, of the stratum from which they protrude. 



e. Fossils, oolitic grains, and mineral crystals are sharply 

 cut off, with no evidence of disturbance, at the contact of the 

 sides of the interpenetrating columns. The missing parts are 

 not to be found. 



/. Large fossil shells are often completely pierced or par- 

 tially penetrated by stylolites. 



g. Adjacent, parallel stylolite-seams often partially pene- 

 trate one another. 



h. The side-surfaces of stylolites are always striated, and 

 mineral deposits on them are slickensided. 



i. Stylolite-columns are not intercemented as should be 

 expected if they were formed in plastic sediment before the 

 cementation and hardening of the rock took place. 



j. Stylolites are found along inclined bedding planes, with 

 their direction of penetration vertical, instead of at right 

 angles to the stratification as the pressure theory would re- 

 quire. 



2. Stylolite-seams are always characterized by a parting 

 of clay which rests as a thin cap at the end of each column. 

 This clay is the solution residue of the dissolved lime-mass. 

 The most important evidence in support of this: 



a. There is a definite relationship between the chemical 

 constituents of the clay and the constituents of the associ- 



