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h''-Kina University Studies 



the solution of lim tone, under pressure, and the resulting 

 production of residual material are geologic processes which 

 may have considerable bearing upon the explanation of vari- 

 ous stratigraphic features and peculiarities of limestones. 

 One can readily see that the occurrence of stylolites, them- 

 selves, indicates a secondary change of no little importance 

 in the parent limestone. Not only are the original limestone 

 strata reduced in thickness (which may be considerable in 

 a highly stylolitic formation), but a secondary clay, of re- 

 sidual origin, is introduced. The writer is firmly convinced 

 that many of the thin clay partings in limestones — always 

 heretofore referred to as sedimentary clays or shales — are 

 of residual origin, produced by solution of the limestone along 

 a bedding plane or lamination plane. Stylolites result where, 

 the limestone exhibits a differential resistance to solution. If 

 the rock on each side of a solution crevice were of uniform 

 resistance, stylolitic interteething would hardly result. Con- 

 tinued solution would give only a slightly undulating seam, 

 with a residual clay parting (see p. 53; also Figs. 20 and 21). 

 The possibilities of secondary modifications of limestone beds 

 by solution, with the production of residual clays, should not 

 be overlooked. 



SUMMARY 



Detailed field investigations of stylolites reveal many fea- 

 tures and complexities which can be satisfactorily explained 

 only by the solution theory — that stylolitic phenomena result 

 from the differential chemical solution of hardened rock, 

 under pressure, on the two sides of a bedding plane, lamina- 

 tion plane, or crevice, the undissolved portions of the one side 

 fitting into the dissolved-out parts of the opposite, the inter- 

 fitting taking place slowly and gradually as solution continues. 

 The clay caps of the stylolites are a residual product of the 

 limestone which has been dissolved. 



A careful study of stylolitic structures discloses many 

 features which are unexplained not only by the older unes- 

 tablished theories, but by the gas theory of Zelger and Potonie, 

 and the pressure theories of Quenstedt, Thurmann, Marsh, 

 Giimbel, and Rothpletz. The writer wishes to present the 

 following summary of the more important observations which 

 conclusively establish the solution theory of the origin of 

 stylolites and oppose the other theories : 



