630 



EEPORT — 1881. 



Somerset. The subject-matter of tlie paper is a very concise description of the 

 areas and extension of tlie divisions ioto which the Devonian rocks are separable 

 upon stratigraphical grounds. The area treated of is embraced in sheets 20, 21, 

 2(3 and 27 of the Ordnance Maps. Of these, the Devonian rocks in sheets 20 and 21 

 had been mapped in detail by the author, whilst in the other sheets their relations 

 had been carefully ascertained. The paper is little more than an index to the 

 notes made by the author in prosecuting his researches in the stratigraphy of the 

 Devonian area.^ 



The classification adopted is as follows : — 



LOWER 

 DEVONIAN 



MIDDLE 

 DEVONIAN 



r Foreland 

 Gkits 



Lynton 

 Beds 



[ Hangman J 

 I Grits 1 



-I Ilfracombe 

 I Slates pass- 



I ING INTO 



\ MoRTE Slates 



PiCKWELL 



Down Beds 



UPPER 



DEVONIAN 



Baggy Beds 



PiLTON Beds 



Red and purplish grits, fine-grained, and in 

 places siliceous. 



Grey, even-bedded and jointed grits, grey 

 schists, and schistose grits with films of 

 calcareous matter. 



Coarse white quartzose, red-speckled grit, in 

 and upon red and grey rather fine-grained 

 grits associated with shaly and slaty beds. 



Grey and silvery slates and shales with 

 arenaceous films, and impersistent bands 

 of limestone passing upward into pale 

 greenish uufossiliferous quartzose slates. 



Indian-red slates upon red, green, and grey 

 grits, with local purple slate basement-beds 

 passing into the Morte Slates. 



Green slates with Lingula ; brown micaceous 

 grits with Cucidlaa ; the positions of these 

 horizons are apparently reversed near Wi- 

 veliscombe. 



Bluish and greenish grey argillaceous slates, 

 with occasional thin films of limestone 

 and masses of grit (as at Braunton, &c.) 



The Foreland Grits occupy an area (superficial) of 30 sq. miles, extending 

 from Countesbury to Duuster. Thej' are faulted against the Lynton Beds, by a 

 great fault, which can be distinctly traced ; but where the latter are entirely cut 

 out by it near Luccott Hill, the faulted junction between the Foreland and 

 Iliingman Grits is very vague, owing to the imperfect nature of the surface 

 ovidence. At Oare, the Foreland Grits are overlain by Lynton Beds on the north 

 fiide of the fault. 



The Lynton Beds occupy an area of about 14 sq. miles ; they do not appear to 

 the east of Luccott Hill; their junction with the Hangman grits is perfectly con- 

 formable, and near Trentishoe there is a very gradual passage. 



The Hangman Grits form the range which includes Dunkery Beacon, also the 

 whole northern part of the Quantocks. Their relations to the Ilfracombe Slates 

 are much complicated by faults around Croydon Hill and on the Quantocks ; and 

 the prevalence of grits in the Ilfracombe series, whilst indicative of lithological 

 assimilation, makes the boundarj' rather indefinite. 



The Ilfracombe and Morte slates occupy a larger part of the Devonian area 

 than any other division. Their lithological characters vary when traced into the 

 Brendon and Quantock districts. Their junction with the Pickwell Down Beds is 

 seldom affected by faults, and in West Somerset usually presents a perfect litho- 

 logical passage through green and purple slates. 



The Pickwell Down Beds in North Devon form a perfectly defined conformable 

 jimction with the Baggy Beds, Indian-red being contrasted with green slates. 

 From North Molton to Wiveliscombe, the relations of the Upper Devonian beds 

 are much complicated by faults. 



The Baggy Beds are well-marked between Baggy Point and Stoke Rivers, but 

 further east thej' are only locally distinguishable, owing to disturbances and the 



' Gcol. Mag., for Oct. 1881, No. 208, p. 4il, 



