Stockdcile: Stylolites 



81 



The clay caps of the styloUtes of the Salem limestone are 

 always thin in comparison with the length of the stylolite 

 (the length of the stylolite gives a fair measure of the amount 

 of solution which has occurred). In the quarry from which 

 the samples of Tables No. 4 and 5 were collected, stylolites 

 about 1 foot in length bear well-compacted clay caps not over 

 % to 1/2 iiich in thickness. In no instance is the clay parting 

 too thick to be explained by the solution theory. The samples 

 in Table No. 6 were collected from an impure stratum of Har- 

 rodsburg limestone. In the decomposition of this limestone, 

 less of the original rock, as compared with the Salem lime- 

 stone, would be lost by solution and a greater proportion left 

 to accumulate as residual clay. Calculations show 73.37 per 

 cent loss (by weight) for the entire rock (column III). The 

 stylolites of this formation bear clay caps of a proportionately 

 greater thickness than those of the Salem limestone. Fairly 

 short, massive stylolites have clay caps up to an inch or more 

 in thickness. 



From the foregoing study of the chemical relations be- 

 tween the clay partings of stylolite-seams and the associated 

 limestones, one can realize the conclusive evidence that the 

 stylolite-clays fulfil the requirements of a residual product of 

 the limestones in which they are found. 



The analyses show that the general assumption, made by 

 Hopkins and other observers, that the black and brown stylo- 

 lite clay partings are of a highly carbonaceous nature, is a 

 faulty one, since the content of volatile and combustible mat- 

 ter (less COo) is less than 20 per cent (see Tables No. 4 and 

 5; column II). In all instances there has been a loss of the 

 volatile and combustible matter of the original rock. This 

 is due to the expected oxidation and volatilization of a por- 

 tion of the carbon content. 



It should be noted that the limestones of Tables No. 4 

 and 5 contain only a trace of ferric oxide (in each instance 

 0.04 per cent) and a much greater amount of ferrous oxide. 

 The analyses reveal further that they contain 0.60 per cent 

 and 0.43 per cent, respectively, of combustible matter (car- 

 bon). The limestone of Table No. 4 is the so-called *'blue" 

 variety, while that of No. 5 is the ''buff" stone. The writer 

 believes that the generally accepted theory that the buff stone 



