406 



EECENT WOEK OP THE G^EOLOGICAL SUEYEY 



Fig. 7. — Vertical Section II. of Silurian Strata from ErihoU to Ulla- 

 pool, showing horizons of Intrusive Boclcs {nmrhed x) in Assynt, 



( Part of GroTip III. ( 



(Sailmhor Group.) 



Group II. 



(Eilean Dubh.) 



Thickness, 



200-300 feet. 



tvM^i-aWTC 



11 



Group I. 

 (Ghrudaidh.) 



Thickness, 

 about 100 feet. 



Berpulite-grit. 

 30 feet. 



" Fucoid-beds." 

 40-50 feet. 



-{ 1. 





{ 



Upper Zone. 



" Pipe Eock." 



Thickness in Assynt, "< 



300 feet; at 

 Ullapool, 250 feet, 



Lower Zone. 

 Thickness in Assynt, j 

 200 feet; at ^ 

 Ullapool, 300 feet. 



Mottled liinestone. (The " Leopard Stone.") 



White limestone. 



Massive limestone, jointed. 



Eusty, flaggy limestone. 

 Dark limestone, with chert. 



White limestone. 

 Dark limestone. 



White limestone. 



White limestone fiiU of worm-casts, with scoriaeeous band. 



Zone 8. — Brecciated dark mottled limestone. 

 1 Zone 7. — Dark or black crumbling mottled limestone, with 

 J bands of coarse and fine oolitic limestone. 



Zone 6. — White limestone, with occasional worm-casts. 

 I Zone 5. — Dark brecciated mottled limestone. 

 I Zone 4. — Flaggy leaden-grey mottled limestone. 

 J_Zone 3. — Dark gritty limestone, with Serpulites. 

 \ Zone 2. — Leaden-grey limestone, weathering yellow or brown. 

 -^LZone 1. — Sandy limestone, with Serpulites. 

 —Chief zone of Serpulites. Massive Grit. 

 — Massive Grit. 



(Calcareous shales and sandstones, with bands of rusty dolo- 

 i mite, with flattened worm-casts. 



Subzone 5. — Massive, purple, friable grit, with vertical pipes, 

 often of different colour from matrix. 



. Subzone 4. — Eibboned quartzite, with pink and white seams; 

 the pipes usually of a different colour from the matrix. 



Horizon of SerpuUtes in the quartzite. 



Subzone 3. — Flaggy quartzite, occasionally false-bedded, with 

 large pipes 3 or 4 inches across. 



Subzone 2. — White quartzite, with pipes about \ inch in dia- 

 meter. 



f Subzone 1. — White saecharoidal quartzite, with small pipes 

 J about \ inch in diameter. 



.False-bedded grits and quartzites, with brecciated conglo- 

 ' merates at the base. 



AECH^AN. 



