404 



RECEXT WOEK OF THE GEOLOGICAL SITEVEY 



Vertical Section I. of Silurian Strata at Durness 

 and Eriboll. 



( 



C. Calcareous 

 Series. 



VII. DuRiNE Group. 



r Fine-grained, light-grey limestones, 



VI. Croisaphuill 

 Group. 



V. Balnakeil 

 Group. 



IV. Sangomore 

 Group. 



III. Sailmhor 

 Group. 



II. Eilean Dubh 

 Group. 



I. Ghrudaidh 

 Group. 



Upper Zone. 



B. Middle Series 



(partly calcareous ._ 



and partly arena- Middle Zoni 



ceous). 



Lower Zone. 



with an occasional dark fossiliferous 

 band. 



c. Pine-grained, cleaved, lilac-coloured 

 limestones, full of flattened worm- 

 casts ; fossils distorted by cleavage. 



h. Alternations of black, dark -grey, and 

 white limestone, with an occasional 

 fossiliferous band, like zone (a) of this 

 group. 



a. Massive, dark-grey limestone, chiefly 

 composed of worm-casts which pro- 

 ject above the matrix on weathered 

 surfaces. Iv'ear the base are several 

 lines of small chert nodules. This is 

 one of the most highly fossiliferous 

 zones in the Durness basin. 



/"Alternations of dark- and light-grey 

 I limestone, highly fossiliferous, with 

 J occasional impure, argillaceous, un- 

 I fossiliferous bauds. Most of the 

 beds are distinctly cleaved, and con- 

 tain few worm-easts. 

 /^Fine granular dolomites, alternating 

 I near the top with cream-coloured or 

 •{ pink limestone. Near the base are 

 I two or more bands of white chert, 

 1^ one of whicli is about 5 feet thick. 

 /'^Massive, crystalline-granular, dolomitic 

 I limestones, occasionally fossiliferous, 

 charged with dark worm-castings set 

 in a grey matrix; large spheroidal 

 masses of chert near the base. This 

 limestone is locally known as "the 

 \^ Leopard Stone." 

 /'Fine-grained, white, flaggy, argillaceous 

 J limestones and calcareous shales. As 

 j yet no fossils have been found in this 

 l^ division. 

 /"Dark leaden-coloured limestones, occa- 



sionally mottled, alternating near 

 the top with white limestone. About 

 80 feet from the base there is a thin 

 band of limestone charged with 

 Serpulites Maccullochii, and a similar 

 band occurs at the base. 



''At the base lies a massive band of 

 quartzite and grit, passing upwards 

 into carious dolomitic grit, crowded in 

 patches with Serpulites Maccullochii, 

 more especially in the decomposed 

 portions (Serpulile-grit). 



' Alternations of brown, flaggy, calcareous, 

 false-bedded grits and quartzites with 

 cleaved shales. 



/^Calcareous mudstones and dolomitic 

 bands, weathering with a rusty brown 

 colour, traversed by numerous worm- 



1 casts, usually flattened, and resemb- 



i ling fucoidal impressions. These beds 

 are often highly cleaved. This and 

 the overlying zone form the " Fucoid- 

 beds " of previous authors. 



