CHAP. VIII.] TEIASSIC PERIOD. 123 



to the Lower Carboniferous series. Such a breccia can 

 only have been formed in close proximity to a shore-line, 

 and the blocks are probably the debris of a cliff that over- 

 hung the waters of the Keuper lake. 



Southward the Keuper marls and sandstones are known 

 to pass beneath Oxfordshire, where their thickness is about 

 400 feet, and it is highly probable that they stretch con- 

 tinuously through Berks and Hants, and beneath the Eng- 

 lish Channel into Normandy, where there is a small area 

 of Trias, consisting of conglomerates, sandstones, and 

 marls. In Jersey also there is a small patch of conglo- 

 merate which is believed to be Triassic. 



Whether Trias exists beneath the London Basin is a 

 moot point ; because it is not yet settled whether the red 

 sandstones and marls which have been found in the deep 

 borings at Richmond, Crossness, and Kentish Town belong 

 to this formation or to the Old Bed Sandstone. The red 

 and yellow sandstones of the Trias and the Upper Old Red 

 are certainly very similar to one another, but it may be 

 observed that no thick deposit of red marl, such as forms 

 the mass of the Keuper, has been met with in these 

 borings, although the red strata traversed at Richmond 

 were over 200 feet thick, and those at Kentish Town 188 

 feet. Further, the Keuper Sandstone group generally 

 maintains a uniform character over considerable areas, 

 whereas the characters of the strata below London vary 

 largely ; at Richmond they are soft variegated sandstones 

 and marls, at Crossness hard quartz sandstones with red 

 and grey shales, and at Kentish Town variously coloured 

 sandstones and clays, with a thin bed of conglomerate. 

 These variations might of course be due to the proximity 

 of a shore-line ; but, considering all the circumstances, 

 and especially the great distance of the sites south-east of 

 any place where Trias is known to exist, I incline to the 

 opinion of Professor Prestwich and others that these 



