A HISTORY OF DEVONSHIRE 



Devonian 



Rocks of 



South 



Devon 



[continued) 



Upper Devonian {continued) . 



Middle Devonian 



Lower Devonian 



In the upper part of limestone masses the con- 

 tinental base of the Upper Devonian is repre- 

 sented by massive limestone, generally coralline 

 (as at lyummaton, Chudleigh, Ilsham, etc.) ; 

 by beds of limestone on shalstein (as at Black- 

 head and Goodrington) 



Bedded limestones, generally coralline, shaly and 

 slaty limestones at base (Eifelian) on slates 



South of Totnes volcanic rocks (Ashprington 

 development) on slates 



Betwreen Totnes and the Plymouth limestone 

 the series is represented by slates with volcanic 

 rocks and local patches of limestone 



Staddon grits. Quartzose grits and sandstones 

 irregularly associated with slates and shales 



Meadfoot, Looe and Ringmore beds. Irregular 

 slates with grit or siltstone beds, slates with 

 siliceous and calcareous films 



Dartmouth slates. Reddish and buff slates, 

 purple-red and green glossy slates, with sili- 

 ceous films and occasional beds of hard grit 



' and quartzite 



Archasan of 



Bonney, etc. 



Altered 



Devonian 



of Hunt, etc. 



Hornblende-Epidote schists. An altered series 

 of basic rocks 



Mica and quartz schists. Altered grits, slates 

 and shales, originally similar in composition 

 to Lower Devonian rocks on the north 



MICA AND QUARTZ SCHISTS AND HORNBLENDE EPIDOTE 



SCHISTS ' 



The mica and quartz schists are a highly altered series of slates or 

 shales, for the most part interbanded with harder siliceous materials 

 (grits or silty bands) of the same types as are encountered in the De- 

 vonian area; their dark grey colour forms a marked contrast to the 

 prevalent green hues of the hornblende-epidote schists in junction 

 sections. The hornblende-epidote schists are a highly altered series of 

 basic rocks, diabases and diabase tuffs similar to those in the Devonian 

 area. They may be termed green schists, although locally exhibiting 

 pronounced red, buff and brown colours, as in the section at Hope. 

 These rocks are the newer group, as in the interfoldings with the mica 

 schists at their junction, in such sections as the Portlemouth Coast and 

 Southpool Creek, they decrease in thickness downward from the surface, 

 the mica schists exhibiting the opposite tendency. At their junction 

 there is often an appearance of interbanding of the green and dark grey 

 schists. 



The mica and quartz schists of the Start Point district are separated 

 from those of the Bolt by a syncline of the green schists, which, running 

 in a north-westerly direction across the Salcombe estuary, coalesces with 

 a band of green schists prolonged westward from the Bickerton valley. 



* See Proc. Geol. Asm. vol. xvii. pt. 3, pp. 119-35. 

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