144 T. C. Hopkins— Stylolites. 



small stone or shell protecting the material underneath, while 

 that surrounding is washed away by the rain in the case of the 

 earth and by the sun on the ice. 



Weiss,* corroborating the above, states that in his observa- 

 tions in a Bundsandstein formation, that a foreign body like a 

 mussel shell or a piece of clay forms a protective covering to 

 the drying lime particles, whereby the drizzling water has 

 modeled out the stylolite by carrying away the material 

 between the protected parts. 



Zelger,f after detailed work on the stylolites, announces that 

 they are formed by the escape of compressed gases through 

 the soft plastic mass and the later filling of the passage-ways. 



Gumbel states that the stylolites, particularly those from 

 Kudersdorf, carry on top a clay cap which without doubt has 

 come from a clay or marl layer which marks the lower limits 

 of the bed of stone bearing the stylolites, and which is a part 

 of the underclay layer ascending with the stylolite mass. 



ZirkelJ says that the stylolites remind one of the phenom- 

 enon called creeps by the English miners, in the swelling up 

 and pressing in of the underclay of the coal into the galleries 

 or openings made in the working until the gallery is filled by 

 the underlying clay. 



Quenstedt states§ that they are due to the filling in of hol- 

 low spaces made in the rock while yet soft by the movements 

 of mussel shells. His later view was that where two beds 

 overlie one another, separated by shells and a layer of clay or 

 marl, the two beds having a different hardness, the pressure of 

 the overlying mass would tear the clay bed and the underlying 

 and overlying beds would be pressed into one another, thus 

 causing the stylolites. 



It will thus be seen that the German writers nearly all agree 

 in thinking that the stylolites are bedding planes but do not 

 agree in the origin of the tooth-like markings. As there is a 

 difference in the appearance of the stylolitic points at different 

 localities so they may be caused by different agencies. Some 

 of them are evidently mud cracks caused either by the sun 

 (Plieninger) or by the frost (Yon Cotta). Some are apparently 

 caused by the action of the rain or spray on the limestone mud 

 (Fallati, Quenstedt, Weiss) ; but some may in part be caused 

 by organisms of some sort (Quenstedt) or by the escape of 

 gases (Zelger) from the plastic mud. 



The cone-in-cone structure closely allied in some respects to 

 the stylolites was not observed anywhere in the oolitic lime- 

 stone district. 



* N. Jahrb. f. Min., 1868, p. 729. 

 \ Ibid.. 1870, p. 833. 



% Lehrbuch der Petrographie, vol. i, p. 536. 



?; X. Jahrb. f. Min., 1837, p. 496, and Wiirttemberg Xaturwiss. Jalireshefte, 

 1853, ix, p. 71, and Epochen der Natur, 1860, p. 200. 



