478 Correspondence — The Wealden of Hanover. 



beds of English geologists, and consisting of thick beds of limestone 

 interstratified with beds of marl, in which are numerous specimens 

 of Exogijra virgula ; fossils are rare, the most abundant is Corbula 

 mosensis, Buv, 



Certainly, these " Miinder, or bunte Wealden-Mergel " m^y be 

 regarded, if the above description is correct, as one of the most 

 anomalous formations hitherto discovered. Though a member of 

 the Wealden, they represent the Purbecks, and contain numerous 

 specimens of a fossil characteristic of the Kimmeridge Clay. 



But this is nothing to what follows, for we read that " they attain 

 a thickness of 120 metres, and belong to the Upper Kimmeridge;" 

 so that the aforesaid " Miinder or bunte Wealden-Mergel," having 

 started as a Wealden formation, which had swallovped up all the 

 Purbecks, now figure in the Upper Kimmeridge. 



But the geological bouleversement of this most extraordinary region 

 is not yet at an end, for we read that " over these " " follow dark- 

 coloured beds, twelve metres in thickness, rich in fossils, as Exogyra 

 virgula, Pecten concentricus, etc., etc.," belonging to the Lower Port- 

 land, succeeded by the Upper Portland, and Serpulit or Purbeck 

 Limestone. 



Now we were told in the first instance that these wonderful Miinder- 

 Mergel represented the Purbeck beds of English geologists, and yet 

 in this last passage they are represented as underlying not only the 

 Purbeck Limestone but both Upper and Lower Portland. Yet, in 

 the very teeth of this statement, we read in the fifth paragraph of the 

 review, that under the lowest member of the Wealden, viz. the 

 Miinder-Mergel, lies the Eimbeckhauser limestone, " which belongs 

 to the Upper Portlandian, representing a portion of the Upper 

 Jura, and forming, it may be, passage-beds from the Portland to 

 the Wealden." So here we have the wonderful Miinder above a 

 member of the Upper Portlandian : in the second paragraph it was 

 beloio the Lower Portland. Unless, therefore, the Lower Portland is 

 above the Upj^er Portlandian, paragraphs 2 and 5 contradict each other. 



This sort of muddle could never haA'e occurred if a proper strati- 

 graphical column had formed part of the work in question. In 

 order to arrive at the real meaning of the author, we append a literal 

 translation of the passage which bears on the subject, followed by 

 a column derived from a subsequent memoir by Herr Struckmann,^ 

 which will represent what Herr Struckmann intended to show : — 



" The Purbeck marls or Miinder-marls, which are to be regarded as 

 the transition steps to the Wealden, follow in regular superstratifi- 

 cation the Upper Portland Beds, as the equivalent of which near 

 Hanover the Eimbeckhauser Plattenkalke show themselves. These 

 conditions of stratification are most distinctly observable in the 

 Kappenberg, which stands out from the southern slope of the Deister 

 between Altenhagen and Nienstedt. On the western and south- 

 western slopes of this ridge, between the village of Altenhagen and 

 the point where the road leading over the height from Nienstedt to 

 Messenkamp descends in various windings into the wide valley 

 ' Neues Jahrb. fiir. Min., etc., 1881, Bd. II. p. 102. 



