Stockdale: Stylolites 



43 



of the same thickness as the adjacent longer ones (see Fig. 

 26). A very thin coating of clay covers the striated side- 

 surfaces of the penetrations, and diminishes in thickness from 

 the end to the base. The color of the clay varies with the color 

 of the stone. Stylolites of the '*buif" stone bear brown caps; 

 those of the ''blue" stone, black caps. Gradations between 

 these are also found. The clay caps often present a compact, 

 laminated appearance. Their line of contact with the end of 

 the column is usually sharp, altho in some instances, the caps 

 appear to grade slightly into the limestone of the column. 



^yy^^-^ .^^ 



^ ^ 



Fig. 16. — Diagram of the small, finely toothed type of stylo- 

 lite-seams. The sutures end in a fine, barely noticeable 

 line. Note the resemblance to the sutures of the human 

 skull. Such a seam represents the ''Drucksuturen" of the 

 German investigators. This specimen is from the Mitchell 

 limestone. Three-fourths natural size. 



Distinct fossils are lacking in the clay, altho corroded frag- 

 ments are often found. Chemical analyses of the clay caps 

 show them to be similar to the residual clays of limestones 

 (see pp. 67-83). 



Relation to Stratification 



' The stylolite-seams of the Harrodsburg, Salem, and 

 Mitchell limestones of Indiana are, in general, horizontal, and 

 parallel with the lines of stratification, usually running along 

 the bedding planes or lamination of the rock. The larger 

 stylolite-seams, especially, often mark stratification planes; 

 and are traceable, with no sharp break, into the common bed- 



7—22663 



