part 3] THE DEVONIAN OF FEKQUES. 233 



Famenniun. 



Fiennes Sandstone. — This is divisible into two parts: the 

 lower is yellow or brown, finely- bedded, sometimes micaceous sand- 

 stone ; the upper is pure white, with a green or grey tinge, finely 

 bedded or apparently compact. The lower beds are seen in two 

 quarries in Beaulieu Wood at Le Hure and at Ferques ; the upper 

 beds in a quarry in Beaulieu Wood, in two quarries at Le Hure, and 

 opposite the crucifix on the high road near Le Hure. They are un- 

 fossiliferous ; but Belleroplion is recorded by Bigaux, and some 

 lamellibranchs by Godwin-Austen. 1 The exposures at Hydrequent, 

 Sainte Godeleine, and Bougefort are of similar rocks, but the white 

 variety is not seen, and the beds appear to be of much greater 

 thickness than the Lower Fiennes Sandstone ; they may, therefore, 

 belong to a higher horizon than the Le Hure beds. OucuUcea 

 hardiiigi, C. 'trapezium, and G. amy g doling, have been recorded 

 from Sainte Godeleine (Godwin-Austen, loc. supra cit.). 



The Upper Famennian is absent, either owing to non-deposition, 

 or to thrust-faulting ; but it may occur under the Jurassic rocks 

 near Sainte Godeleine. 



The maximum thickness in the main area of these sandstones is 

 585 feet. 



Tectonic Structure. 



The lowest beds of the Devonian System which are exposed 

 consist of a coarse conglomerate with rounded pebbles. Within 

 half a mile Lower Balaeozoie rocks have been detected in a boring, 

 which are identified by the presence of a graptolite : D. Sharpe ' 2 

 was of opinion that the remains were those of plants, but his 

 opinion has not been supported. These two facts point to the 

 proximity of a Lower Bakeozoic coast-line and the absence of 

 the Lower Devonian rocks in this area, unless they are covered by 

 overlapping of the higher beds. The Devonian rocks, therefore, 

 rest unconformably on an old Lower Balaeozoie surface, of wdiich 

 the coast-line ran close to the northern limit of this Balaeozoie area. 

 The Devonian beds rest conformably on each other, with the 

 exception of a few thrust-planes of very small throw. They are, 

 however, traversed by a large number of dip-faults, which give a 

 more northerly trend to the general direction of the strata than 

 their strike. These faults are confined to the Devonian rocks, and 

 are therefore of pre-Jurassic age. 



In the southern direction the Devonian strata end against the 

 Carboniferous dolomite ; but careful mapping shows an uncon- 

 formity at the junction, the strikes of the Devonian and Carbon- 

 iferous rocks being at various angles, differing by about 60°. In 

 addition, the dip-faults end at the junction with the Carboniferous. 



1 Q. J. G. S. vol. ix (1853) p. 239. 



2 Ibid. p. 249. 



