The Polar and Kuribrong Rivers. 161 



one strikes across the river from east to west. Between these dykes and 

 above them exposm-es of altered porphyrite occur, and at a distance of 

 about a [[uarter of a mile from the creek a very fine-grained compact felsite 

 is exposed, which has a red-chocolate colour, and much resembles the 

 so-called "jasper " commonly found in placer-gravels. This is probably 

 a quartz-porphyry altered by contact with diabase. It is traversed by 

 a dyke of diabase trending north and south across the river, which has 

 here a local direction of east and west. For a distance of about one 

 and a half miles, to near Oewang Creek, quartz-pox'phyry and poi'phyrite, 

 more or less altered, occur. Near Oewang Creek a l)road belt of 

 epidiorite is traversed by the river, and the rocks in ifc are covered 

 with ironstone-conglomerate. Opposite Oewang Creek, and for about 

 half a mile south of it, epidiorite is seen at intervals, the general trend 

 of the rocks being north and south. For abofijt a mile to tne south of 

 this place more or less altered porphyrites occur, and about a quarter of 

 a mile below Amatuk Falls, on the east bank of the river, a coarse 

 quartz-granophyre underlies sandstones which dip to the south-west. 



On the west bank, at a little distance below Amatuk Falls, there is a 

 mass of diabase. On the same bank at the foot of the Amatuk Falls, 

 when the river is low, a greenish rock is exposed, which is an altered 

 23orphyrite. This passes into a reddish-brown, more or less foliated rock, 

 jirobably an indurated felsitic mud, or possibly a feldspathic tuff. Upon 

 this, in places, masses of quartz are found, having a fluted structure 

 repeated over many parallel layers. These flutings are casts of mark- 

 ings of a slickenside-nature impressed originally on the soft mud which 

 here formed the base of the sandstone, and now preserved in secondary 

 quartz. Amatuk Falls are over some of the lower beds of the great 

 sandstone and conglomerate formation. Here the sandstone is fine- 

 grained, with occasional quartz-pebbles, of a red colour, and shows 

 very clearly, and in places markedly, current-bedding. Not more than 

 about twenty five feet of the lower beds are exposed in the actual 

 section at the falls. A sill of diabase intrusive through the sandstone 

 causes small rapids above the main fall. 



For a little over a mile along the course of the river above Amatuk 

 Falls the rocks exposed on the banks of the river are sandstone, and the 

 cliffs and the mountains consisting of this. There is an exposure on 

 the south-west bank of the river, and on a small island in it, of a 

 very coarse-grained enstatite-diabase, intrusive through the sandstone. 

 A little distance from here the river flows round the foot of a 

 great mountain, which shows remarkable cliff-faces of sandstone form- 

 ing vertical precipices over a thousand feet in height, the mountain 

 itself being probably more than two thousand feet high. The river 

 here passes over quartz-porphyry, which underlies the sandstone. 

 Beyond this place coarse sandstone resembling quartzite is seen on its 

 banks. About two miles from the exposure of quartz-porphyry a 

 broad dyke of diabase crosses the river from north-east to south-west, 

 giving rise to small rapids near Waracabra Island, which itself con- 

 sists of this rock. The diabase is very coarse and granular, in structure 

 approaching a gabbro. 



M 



