362 A. Vaiig/iaii Jennings — Geology of Bad NauJieim. 



fairly satisfactory at first siglit, but on study is found to contain 

 serious difficulties. The ' Stringoceplialen-kalk ' on the right can 

 hardly be accounted for without any corresponding mass on the 

 left ; and the theory requires that the dip of the ' Taunus-quarzit ' 

 on the east slope of the Johannisberg should be represented in exactly 

 the reverse direction to what is actually the case. More serious still 

 is the diflSculty that it places the ' Taunus-quarzit' above the other 

 members of the Devonian, whereas it really underlies all but the 

 'Sericit-schiefer.' 



, Under these circumstances I thought one might try to make 

 a hypothetical section which would better fit in with the known 

 data ; and it seems to me that some such structure as is shown ia 

 Fig. 5 would meet the requirements of the case. It is not necessarily 

 true, as there maj' be considerable faulting, but until there is evidence 

 of the presence of faults it is as well to try to explain matters 

 without their help. 



An infolding such as this is just what might be expected from 

 the structure of the Taunus range as a whole. The peculiarities 

 of the boring records are easily accounted for on this supposition, 

 and several other isolated facts fall readily into place. Thus, if it is 

 true that boring 10 in the plain on the east passed through ' Sericit- 

 schiefer ' and then touched the ' Taunus-quarzit,' such is what 

 might have been expected, as is shown in Fig. 5. Similarly, the 

 reported outcrop of ' Orthoceras-schiefer ' near the Teich-haus is 

 by no means impossible ; while the patches of the same rock and 

 of ' Spiriferen-saudstein ' mapped to the west of Ober Morlen can 

 also be accounted for as an infold similar to that below Nauheim. 



(6) Passing on from the question of these contorted Devonians to 

 the simply and conformably stratified Tertiary beds of the Wetterau 

 plains, one expects a simplification of the task of explanation. 

 Such there is to a certain extent ; but, on the other hand, there are 

 new questions of a totally difiierent character which crop up in the 

 endeavour to follow out the history of the country. 



While there can be no doubt that the area over which these 

 deposits extend was in Middle Tertiary times an enclosed lake, yet 

 the stages which preceded the isolation of this extent of water are 

 not so easily recognizable. 



The fact that mollusca characteristic of brackish water — such as 

 Cyrena, CeriOiium, and Litorhiella — are found in beds as high as the 

 Biiittersandstein, is somewhat remarkable in itself. When we find^ 

 moreover, that in the deeper layers there is a much larger percentage 

 of such types, and finally in the lowest strata we have to deal with 

 typically marine genera, it is evident that the succession of beds 

 records a series of great physiographic changes. It seems almost 

 certain that in Oligoceue times these districts were covered by 

 sea-waters from the soutli ; and the contours of Central and Northern 

 Europe suggest a similar communication with the ocean on the north. 



It seems probable that the district was a dry land area, while the 

 Cretaceous rocks of other parts of Germany were being deposited ; 

 that an Eocene or post-Eocene subsidence let in the sea- water from 



