BY W. N. BENSON. 571 



waters of that creek from capture by the Duncan's Creek 

 System. On the other hand, the ferruginous content of the 

 jasper may increase till the rock becomes merely a siliceous 

 haematite. This, however, is unusual. Very ferruginous phyllite 

 is more common, and passages from this into a jasperoid rock 

 are frequently observable. 



Between the jaspers, are normal micaceous phyllites and vary- 

 ing types of green and purple schistose tuff that have not as yet 

 been much investigated. Spilites are common in varying stages 

 of alteration. In the field, before microscopic investigation had 

 shown their nature, they were a great puzzle, and were considered 

 to be a dark-coloured hornfels. They are all fine-grained, often 

 slightly vesicular, and break with difficulty, giving an irregular 

 fracture. They are much sheared and jointed, and, in some 

 forms of alteration, strongly resemble altered mud stone. They 

 have been found in various localities, and are particularly abund- 

 ant on the slopes east of Munro's Creek, where they are invaded 

 by the porphyries. Here they are probably the predominant 

 rock, and are, no doubt, far more abundant elsewhere than is at 

 present known. 



Between the head of Munro's Creek and Swamp Creek, there 

 is a wedge-shaped area of Woolomin rocks differing from those 

 described above, but resembling what may be found near Mun- 

 dowey, on the Namoi River. This area has not been much 

 investigated, and is doubly difficult of study owing to its poverty 

 in good outcrops, and the thickness of the vegetation. A peculiar 

 slatey conglomerate forms the northern portion, and stretches 

 from north of Folly Creek down to Nuggety Creek, along its 

 western tributary; while hence, to the south and east, a tough, 

 grey, non-schistose hornstone is present, suggesting an altered 

 microcrystalline rock porphyritic in quartz, but which, on micro- 

 scopic examination, is clearly clastic. A similar rock occurs at 

 Mundowey. A little inlier of this rock is to be found among 

 the basalts near the head of Swamp Creek (here called Burrows' 

 Creek). It is quite impossible, so far, to make any statement of 

 the stratigraphy of this much disturbed area. Many of the dips 

 recorded are probably only cleavage-plane slopes, but wherever 



