CHARACTER OF TRANSITION ZONE 289 



It is frequently called the Devono-Carboniferous zone. The general asser- 

 tion is that it can not be referred to either one of the two great systems. 

 Only the bare statement exists and is reiterated. The facts as now known 

 give small grounds for the assertion. 



If the basal plane of the Carboniferous be taken as the bottom of the 

 original Kinderhook, the forms of the succession of layers certainly do 

 appear to be in unbroken sequence. According to the evidence here 

 presented, the succession of fossils clearly indicates that the faunal occu- 

 pancy of the region was at that time more than merely sequential — it 

 was genetic. 



If, however, we proceed on the hypothesis that the base of the Chou- 

 teau limestone should be considered the real bottom of the Carboniferous 

 system, we find an entirely different group of circumstances prevailing. 

 The higher fauna is manifestly not the direct genetic successor of the 

 lower one. It is essentially alien. The biotic change at this level is as 

 abrupt as the lithologic one. There is practically no transition zone at 

 all. The line demarkating the faunas is sharply defined, There are, 

 moreover, physiographic reasons for believing that an important strati- 

 graphic line should be here drawn. 



In southwest Missouri, where the mergence of faunal elements into a 

 Devono-Carboniferous zone has been most urged, similar conditions and 

 similar facts appear to obtain. A mingling of faunas in the zone under 

 consideration may be a feature, but it is a feature that never has im- 

 pressed any one who is familiar with the faunal elements of the more 

 northern strata generally called Devonian. Moreover, as already stated, 

 Williams* has recently urged the faunal parallelism of the Sylamore 

 sandstone and the accompanying shales of Arkansas with the Louisiana 

 limestone of northeast Missouri. When it is remembered that the de- 

 scribed fauna of the Louisiana limestone is really the fauna of the shales 

 underlying, the real force of this statement will be at once apparent. 



The character of the so-called transition zone is viewed in another light 

 from that which it has been ordinarily when it is considered that the 

 present Ozark uplift has not been a land elevation ever since pre-Cam- 

 brian times, but, as recently t shown, is of comparatively late origin. 



Peculiarities of the original Kinderhook 



The main reason for the general confusion which has so long prevailed 

 regarding the limitations of the formations here regarded as properly 

 belonging to the Interval deposits is no doubt the lack of exact field data 



*Arkansas Geol. Survey, Ann. Rept. 1892, vol. v, 1900, p. 318. 

 t Science, N. S., vol. vii, 1898, p. 588. 



