305 



sand and gravel were spread over some portions of the sur- 

 face. Recent deposits consist of the stream gravels and 



Igneous Geology. — In the Arisaig region in the interval 

 between the Lower Ordovician and Silurian and again 

 during the Mississippian period there were intrusions of 

 varied rock types. The Lower Ordovician rocks at some 

 time subsequent to the deposition of the James River beds, 

 but apparently before the laying down of the Malignant 

 Cove conglomerate were intruded by quite large masses 

 of granite and monzonite. Where fresh the granite is of 

 a bright, flesh-red colour, very compact, tough and fine- 

 grained and contains feldspar and quartz in the ratio of 

 about 2 to I . The areas of outcrop are south of Malignant 

 cove and the intrusion appears to be in the form of a stock. 

 The time of the intrusion was certainly subsequent to 

 James River deposition and perhaps also Baxter's Brook, 

 but prior to Malignant Cove time, since in thin sections 

 of the last, Williams has found particles derived from the 

 granites. 



The monzonite outcrops on the shore about one half 

 mile east of Malignant Cove. The intrusion appears to be 

 in the form of a stock and consists of a medium granular 

 rock in which white plagioclase feldspar and green horn- 

 blende are the chief constituents. The colour is a mottled 

 green and white. Fragments of this rock are in the Malig- 

 nant Cove conglomerate so that the time of the intrusion is 

 probably to be placed in the same interval as the granite 

 intrusives. 



At the base of the Silurian section are splendid expos- 

 ures of the upturned and eroded edges of a devitrified rhyolite 

 flow. In places this passes into a flow breccia and at 

 Frenchman's Barn, a large knob of rhyolite about a mile 

 east of Arisaig village, there are considerable masses of 

 breccia which may be the result of explosive action, but 

 which Williams also considers flow breccias. Historically 

 the rhyolite is of interest since it was considered by the 

 earlier workers as having been produced by the metam- 

 orphism of sediments and Eozoon was reported from some 

 portions of it. Cutting the rhyolite are large dykes of 

 amygdaloidal diabase and a dyke of red shaly rock 

 which cuts both rhyolite and diabase. In places the rhyo- 

 lite shows flow structure and the color varies from grey 

 35063— 7A 



