16 



Indiana University Studies 



being distinctly columnar in form with parallel sides, as are 

 stylolites, are often more or less conically pointed (see Figs. 

 14 and 16). As in the case of stylolites, **Drucksuturen" are 

 characterized by the ever-present clay partings (oftentimes 

 only minutely visible) and the finely striated side-surfaces 

 of the interpenetrated parts. The primary distinction, there- 

 fore, between "Drucksuturen" and stylolites, is one of size. 



Many early investigators held ''Drucksuturen" and stylo- 

 lites to be of different origin. The latest to distinguish sharply 

 between the two was Rothpletz (1894, 1900). In his most 

 recent discussion he arrived at the conclusion that *'Druck- 

 suturen" and ''Stylolithen" are ''morphologically and genetic- 

 ally" quite different — the first is the result of rock pressure 

 and solution in the hardened limestone mass; the second, the 

 result of the pressure of the overlying sediments in a plastic, 

 unhardened limestone deposit. The associated clay film of 

 the ''Drucksuturen", according to Rothpletz, is the solution 

 residue of the dissolved lime mass. Rothpletz came to this 

 conclusion after a careful study of the fossils found with the 

 phenomena, which showed distinct signs of corrosion. Ex- 

 amples of fossils which were partially removed, or entirely 

 penetrated by the teeth of the ''Drucksuturen" were observed.^ 



The most recent investigators, especially Fuchs, Reis, and 

 Wagner, hold ''Drucksuturen" and ''Stylolithen" to be anal- 

 ogous phenomena, and do not accept the distinction made by 

 Rothpletz. They attribute to both phenomena the same origin 

 and consider ''Drucksuturen" merely as ''young" stylolites — 

 the beginnings of typical stylolite-seams. 



2. "Gerolleindriicke" (Impressed, or Pitted, Pebbles) 



Occurring in conglomerates of various geologic ages are 

 found pebbles marked with depressions, or pittings, the 

 origin of which probably has a bearing upon that of stylo- 

 lites. These impressions are of two principal kinds : (a) one 

 which bears evidence that it was produced by the squeeze, 

 or pressure, of the contacting pebble, since the impressed 

 pebble is highly fractured, the fractures radiating from the 

 center of the pitting (see Fig. 7) ; (b) the second, a smooth, 

 sharp type of pitting, which was apparently formed from tho 

 actual hollowing out and removal of the material formerly 



^ The work of Rothpletz on "Drucksuturen" is carefully reviewed by Wagner (1913, 

 pp. 102, 103, 109). A discussion of Rothpletz's theory as to the origin of the so-called 

 "Stylolithen" is tal^cn up later, under the heading "Pressure Theory", p. 28. 



