REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1903 111 



present, had suddenly given place to black, thin laminated mud, 

 and above to harder, thin bedded ferruginous shale, the mud 

 seams abutting against the gypsum and slate in a reentrant 

 fashion. The lamination of the mud appeared to correspond to 

 that of the gypsum against which it abutted, and one block vras 

 hard gypsum at one end and black laminated mud at the other, 

 although elsewhere the gypsum and the mud were separated 

 by irregular joint-like cracks. I was inclined to attribute the 

 change to the action of water penetrating to the beds through 

 crevices in the clay cover. 



The limestone of that part of the series in question which en- 

 closes the gypsum beds is of a prevailing drab or ash color, with 

 a few blue seams, of which no. 2 of the section is the only import- 

 ant one. It is often highly laminated, has a considerable amount 

 of impurities as has already been said, and by reason of the 

 earthy character of these impurities, it shows such a disposition 

 to absorb water as to unfit it for all but the roughest purposes. 

 A fragment of no. 1 gained in weight Sfo by two hours' soaking, 

 while a like fragment of the blue limestone no. 2 showed no ap- 

 preciable gain in the same time. 



The character of the limestones just described seems to me to 

 throw light on the question of the origin of the gypsum beds; 

 these I think have obviously been formed from the earthy drab 

 limestone of the horizon at which they appear, as the result of the 

 action upon them of acid waters originating in sulfur springs, 

 which are still somewhat abundant in this region, and which it 

 may be presumed w^ere more abundant at an earlier geological 

 date. The porous character of the drab colored limestones would 

 facilitate such transformation, under favorable circumstances; 

 while the imperviousness of the blue limestone which underlies 

 the series would limit it below. Reasons for this opinion as to 

 the origin may ibe found : first^ in the striking similarity in struc- 

 ture between the lower gypsum and the associated drab lime- 

 stones, both having the same highly laminated character, while 

 both the lower gypsum and the northern part of the upper, are 

 also distinctly bedded; second, in the structure of the inter- 

 mediate bed, containing as it does alternate layers of gypsum and 

 shale, as if whatever was lime in an imipure shaly lime- 

 stone had been transformed to gypsum, leaving the remainder 

 unchanged ; tliird^ in the presence in all the gypsum beds of native 

 sulfur, which would be difficult to account for on any theory of 

 origin which would not include the action of sulf ureted waters ; 

 fourth, in the composition of the gypsum itself, which is gray, 

 and like the limestones somewhat impure, containing in com- 



