part 2] THE METAMORPHOSED ROCKS OF THE START AREA. 175 



Green Schists formed a syncline from their union near Malborough 

 to the Bolt Tail. He considered that 



' the Green Schists may unhesitatingly be regarded as an altered series of 

 basic igneous rocks allied to the diabases in composition, and possibly 

 consisting in part of altered tuffs ' (op. cit. p. 37). 



I am of opinion that an adequate explanation of the structure 

 and stratigraphy of this district can only be obtained by recognizing; 

 both an upper and a lower group of mica -schists. 



Across the strike from their boundary with undoubted Devonian 

 rocks the Start rocks have a width of outcrop attaining a maximum 

 of 3 miles to Prawle Point, and approximately 2| miles to Bolt 

 Head, the southernmost headland of the western area. Along the 

 strike, and approximately coinciding with the structural axis of the' 

 district, they stretch from Bolt Tail to Start Point, the eastern- 

 most promontory — a distance of nearly 10| miles. 



For purposes of description, the district may be divided into two> 

 areas, the one covering the rocks developed east of the Salcombe' 

 estuary, and the other the region stretching from Salcombe to- 

 Bolt Tail and the village of Hope. 



It is clear from Ussher's mapping that a single major band of 

 Green Schist is developed, which, on account of folding, is split \ip 

 into two bands, one forming the southern coast of the eastern area, 

 while its northern branch runs in proximity to the southern out- 

 crops of the definitely determined Devonian slates and phyllites. 



The following succession is represented in ascending sequence : — - 



(a) Start Mica-Schists. 

 (5) Green Schists, 

 (c) Bolt Mica-Schists, 



Area East of the Salcombe Estuary. 



East of the Salcombe estuary the Green Schists form two distinct 

 and separate bands, the southern striking eastwards to Prawle 

 Point, and the northern band being developed along the Southpool 

 creek, and at Scoble Point, striking eastwards to the village of Hall 

 Sands. 



Investigation of the Green Schists shows that they are to be 

 regarded in large part as dynamically metamorphosed lava-flows — 

 possibly associated with sill intrusions — and beds of composite 

 origin, basic ashes containing the detrital material of normal 

 sediments. The evidence upon which this conclusion rests will be 

 given in the petrographical section of this paper. Ussher's mapping 

 makes it clear that the Green Schists form an excellent datum-line 

 for the elucidation of the structure of the district. 



There is every reason to believe that east of the Salcombe estuary 

 the disposition of the rocks is anticlinorial, the mica- and quartz- 

 mica-schists at Portlemouth and Start Point forming the core of 

 the anticlinorium, and the Green Schists resting upon them. 



There can be no doubt that the mica-schists and Green Schists 



