563 



limestones on their northern boundary), are in places much 

 sheared, and exhibit evidences of great physical strain. It is 

 this belt of country that to the eastward cuts off the main 

 limestone at its most southerly limits. 



Above the waterfall, at the next bend in the Mount 

 Creek, there are typical purple-slates, followed by bluish and 

 reddish quartzites, the latter sometimes coarse and gritty 

 (dip, N. 25° W. at 75°) ; and at the sharp angle, where the 

 creek comes round from the southern end of the mount, there 

 are bluish and very siliceous slates (belonging to the same 

 series), with a dip N. 10° W. at 80°. At this angle the 

 purple-slates series is bounded on its western side by crushed 

 slate, which separates the former from the main quartzite of 

 the mount. 



III. — Igneous Intrusions^ 



These, so far as observed, are limited to the south-eastern 

 side of the mount, and are included within an area of about 

 a mile long and half a mile wide. The outcrops appear as 

 small disconnected pipes rather than dykes, and may repre- 

 sent small necks or fissure-vents of a multiplex volcanic centre. 

 Considering the greatly-broken field in which they occur it is 

 possible that their fragmentary character arises in part from 

 fracture and displacement similar to that which has occurred 

 with the associated sedimentary rocks. 



With one or two exceptions, the igneous rocks are of a 

 T>asic type, and exhibit (with some variations as to texture) 

 a uniform character. All the outcrops have suffered more 

 or less decomposition from weathering. Secondary develop- 

 ments of chlorite, uralite, and epidote are commonly present. 

 Specular hematite, as well as micaceous hematite, frequently 

 occurs in plates or nests, and sometimes in the form of feathery 

 crystals on the face of the joints. Spheroidal weathering 

 occurs, and in some cases the basic rock has become so rotten 

 as to be easily crumbled to fragments by the fingers. 



More than twenty of these volcanic necks or fragments 

 were noted and mapped, and are briefly described below. 

 The numbering refers to the figures on the map. 



Group (a) — on the northern side of the cathedral-rock 



CREEK. 



IVos. 1 and 2. — Two outcrops of a rock of gabbro type 

 occur on the crest of the inner foot hills, on the northern 

 side of the Cathedral-rock Creek. They probably form a 

 single mass, but are separated in their outcrops by a small 

 depression of grassy soil-cover that obscures their union. 

 Unitedly they cover a surface of about 100 yards each way. 



