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Indiana University Studies 



integral parts. The texture of the stone varies from the ex- 

 ceedingly fine-grained lithographic form, thru a typical oolite, 

 to brecciated limestone, ending with an edgewise conglomerate. 

 Thin shale and sandstone partings are to be found.*^ 



GENERAL DESCRIPTION OF INDIANA STYLOLITES 



The Indiana limestones afford abundant opportunity for a 

 study of stylolites and stylolite-seams of various sizes, types, 

 and complexities. The largest stylolites observed by the 

 writer are 13 inches in length (see Fig. 12) ; some are so small 

 as to be seen distinctly only under a hand-lens. The length 

 of the seams is in proportion to the size of the stylolites — 

 the larger stylolites constituting partings of greater extent 

 than small stylolites. All stylolite-seams, instead of ending 

 abruptly, grade into smaller and smaller sutures, and finally 

 disappear as a barely noticeable line. 



In what might be called the most perfect, but not the most 

 common stylolite-seams, the interlocked parts are more or 

 less columnar in shape, the downward and upward projections 

 alternately interpenetrating with much regularity. The as- 

 sumption, suggested by Marsh, Giimbel, and Rothpletz — that 

 few stylolites extend from the upper layer into the lower — 

 will not hold for the Indiana limestones. If one considers the 

 upward-penetrating columns as stylolites, then the adjacent 

 downward-pointing parts must be considered as reciprocal 

 stylolites. In the larger sutures are often found these most 

 perfectly column-shaped stylolites. They are especially sharply 

 defined in the Salem limestone of the Dark Hollow district 

 (see Figs. 2 and 11). The side-surfaces are often parallel; 

 are always well striated, often having a polished or slicken- 

 sided appearance, especially if there is a thin deposit of calcite 

 on them; and are often covered with a very thin coating of 

 clay, drawn from the clay cap to the base of the column. The 

 ends of these columns are convex, fitting closely into the con- 

 cave openings of the penetrated rock, and separated from 

 them by the caps of clay. 



Many common variations from this above-described, ideal 

 type of stylolite are found. In their more common and typical 

 development, the interpenetrating parts occur with less regu- 



^ For a description of the Mitchell limestone, reference should be made to : Beede, 

 J.W., 1915, pp. 206-212. 



