250 C. E. Be Ranee — Deposition of Cretaceous Strata. 



and is probably of post- Jurassic age; they cut off tbe post-Carbon- 

 iferous E.N.E. faults equally with the post-Permian N. and S. faults. 



Sir H. de la Becbe regarded the depression that occurred after 

 the deposition of the Wealden beds as of probably small extent, 

 and believed the beds overlying them denoted " comparatively quiet 

 accumulation of sedimentary matter . . . subsequently to the change, 

 as previously," and he remarks on the absence of " coarse detrital 

 beds resting upon the upturned Wealden deposits." And he states 

 that "we are led to suppose that the change may, geologically 

 speaking, have been gradual ; and that subsequently to the gradual 

 rise of a portion of Western Europe, which brought a part at least 

 of the Oolitic series above the sea, a gradual depression took place, 

 which permitted the Chalk and Greensand to overspread a wide area, 

 covering up a variety of older rocks. Under this view we should 

 expect the beds forming the lowest portion of the Greensand to be best 

 developed when the depression beneath the sea was first effected, 

 and that consequently the higher beds would be most continuous 

 over the area subsequently occupied by the whole Cretaceous series, 

 due allowances being made (more particularly as to the sands and 

 clays) for variations caused by the operation of modifying conditions 



in horizontal distances And we might expect .... that while 



the lowest beds of the Greensand were accumulating in the East 

 of England, dry land still existed in the West."^ 



This depression would appear to have begun in the Yorkshire and 

 Lincolnshire area, where the lower Neocomian beds are so exten- 

 sively developed, and probably also under Norfolk, where the bare 

 Chalk occurs (Norwich well) at a depth loider than the old rocks 

 of Harwich. The line of greatest depression probably extended along 

 an axis ranging from the Humber across the German Ocean to 

 Hanover ; and the subsidence appears to have been more extensive 

 on the Southern than on the South-west margin of the basin. 



The continental epoch, with large inland seas and lakes, which Prof. 

 Eamsay has shown commenced with the Old Bed Sandstone era, 

 appears not only to have lasted up to the close occupied by the 

 deposition of Triassic times, but to have continued, though with 

 more limited area, during the Liassic and Oolitic periods, when 

 it again gained in area, and was drained by a large continental 

 river, in the delta of which were formed the Purbeck and Wealden 

 beds. A movement of subsidence set in to the East, which gradually 

 extended to the West, introducing marine conditions, the strata 

 of the entire Cretaceous system exhibiting a gradually deepening 

 sea-bottom. 



Did the continental land wholly disappear beneath the waves at 

 the close of the Wealden era? The researches of Mr. Judd have 

 shown that the Wealden of Germany was deposited by a distinct 

 river from that which formed the deposits of that age in England and 

 France, and that the highest or newest portion is present in France, 

 being often merely a subordinate to marine beds of Neocomian age ; 

 and he points out with great force the truth of Prof. Huxley's 

 1 Eeport on the Geology of Cornwall, Devon, and "West Somerset, 1839. 



