Maeyland Geological Survey 101 



The discussions of the age of the Wealden rival in volume those of 

 the Ehsetic, Hercynian, and Laramie questions. As transitional deposits 

 the Wealden may well be partly of Jurassic age, but of late years it has 

 come to be accepted as a non-marine facies of the Neocomian, since, where 

 it is present, the lowest marine beds of the ISTeocomian are said to be 

 absent. That the flora (Seward, Ward) and fauna (Smith Woodward, 

 Marsh) are Jurassic in type is not to be wondered at, indeed it would 

 be remarkable if it were otherwise, since Nature knows no units, and 

 boundary lines in conformable deposits are purely utilitarian or academic. 

 This being true, international rather than provincial usage should prevail, 

 and a unified time scale becomes an urgent necessity. 



In the recent masterly summary by Emile Hang (Traite, 1910) the 

 Cretaceous is divided into three major divisions — the Eo-, Meso-, and 

 !N'eo cretaceous ; the Eocretaceous corresponding to the original usage of the 

 Neocomian, the Mesocretaceous being made up of the Albian, Ceno- 

 manian and Turonian stages. This treatment has much to commend 

 it, as can be appreciated by an inspection of Haug's tables of the range 

 of the characteristic fossils. The paleobotanical evidence, while less full, 

 lends considerable support to such an arrangement, which is also in ac- 

 cord with the diastrophic fact that the extensive transgression of the sea 

 which culminated in the Upper Cretaceous was inaugurated in Albian 

 time. 



Lower Cretaceous deposits of various ages occupy large areas in South 

 America, Asia, and Australia, and doubtless in time, as a result of more 

 detailed examination, they will yield their quota toward the completion 

 of the records of distribution of the Cretaceous floras. 



The ISrEOCOMiAN Stage ^ 

 The name we owe in the first instance to Thurmann (1835). It is 

 derived from ISTeuchatel (Neocomum), the marine beds of this stage being 

 typically developed in the Swiss area. 



^ This term is used throughout in the restricted sense as consisting of the 

 etages Valanginian and Hauterivian and not as synonymous or coextensive 

 with Eo- or Palseo-cretaceous. 



