Stockdale: Stylolites 



79 



it is seen that the behavior of the iron content is as should 

 be expected in the transformation of a Hmestone to its residual 

 clay. 



In considering the proportionate amount of lime, one finds 

 that the greatest percentage of that of the parent rock has 

 been lost — assuming, of course, that the clays are of residual 

 origin. The analyses show a loss of 93.20 per cent, 93.40 per 

 cent, and 87.70 per cent in Tables No. 4, 5, and 6 respectively 

 (column V) . This is hardly as great a loss of lime as usually 

 is found in the decomposition of limestone, altho it compares 

 very favorably with some analyses. The lime content of the 

 clay can readily be accounted for by the occurrence of cor- 

 roded fossil fragments which have not been completely dis- 

 solved (see p. 85), and also by the fact that difficulty is 

 found in collecting clay which is entirely free from particles 

 of the adjacent country rock. In the second place, one should 

 hardly expect as thoro a leaching of the calcium carbonate 

 of a stylolite clay seam as that of a residual limestone soil. 

 Residual limestone clays are formed on top of the bed rock 

 and are continually being acted upon by fresh meteoric 

 waters; while stylolite-clays, which occur within the strata, 

 are subjected to the action of waters which have passed thru 

 the overlying bed rock and are already more or less saturated 

 with calcium carbonate. 



The analyses also show the expected loss of magnesia. In 

 Tables No. 4 and 6 the amount of magnesia lost is somewhat 

 less than that of lime, while in No. 5 it is slightly greater. 

 The tables also show that most of the carbon dioxide was 

 lost — 92.90 per cent, 95.10 per cent, and 87.50 per cent in 

 Tables No. 4, 5, and 6, respectively. The carbon dioxide con- 

 tent of a residual clay is dependent, principally, upon the 

 amount of lime and magnesia with which it is united as car- 

 bonates. The analyses show further that the loss of potash 

 and soda is as should be expected in the decomposition of a 

 limestone. These two constituents, being less soluble than 

 lime or magnesia, would normally be retained in greater 

 quantities. 



Table No. 7 is compiled for a comparison of the percent- 

 ages of various constituents lost. The first three columns 

 (taken from Tables No. 1, 2, and 3) show the percentages of 

 the materials lost in the transformation of limestone to re- 

 sidual clay soil; while the last three columns (taken from 



