28 THE VICTORIAN NATURALIST. [Vol. XXIV 



In the Moroka valley, not far from its head waters, and near to 

 the spot where it makes its great easterly bend across the 

 northern extremity of the Wellington Range, below the Trig. 

 Station, a fine dip face of the rhyolite is exposed, passing under 

 a thick bed of conglomerate. A tributary stream of the Moroka 

 comes down over the rhyolite rock face and forms an attractive 

 cascade at this spot. Other sections, as at Snowy Bluff, show the 

 rhyolite resting conformably on conglomerate. Many features 

 point to the fact that these lavas were, in part at least, sub-aqueous. 

 Shallow water conditions appear to have largely prevailed, for 

 numerous examples of current bedding and contemporaneous 

 erosion are to be seen in the sedimentary beds. Many of the 

 conglomerates contain both angular and waterworn fragments of 

 the Upper Palaeozoic series. In some of the upper bands pieces 

 of rhyolite are of fairly frequent occurrence. This was noted at 

 several places, notably on the Welhngton snow plain, near the 

 head waters of Nigothoruk Creek. Again, on the Wellington 

 River, about a mile below the Dolodrook junction, a striking 

 breccio-conglomerate abuts on the contorted and crushed Ordo- 

 vician slates. The Upper Palaeozoic beds here contain abundant 

 fragments of black slate, quartzite, and both angular and rounded 

 pieces of rhyolite up to eighteen inches in length. These frag- 

 mental beds, though apparently at the base here of the Upper 

 Palaeozoic, are inclined at an angle of 40° to 50° to S.W., and are 

 evidently faulted against the Ordovician slates, so that their exact 

 position in the Upper Palaeozoic series is not clear. 



In the Moroka valley some sections, in several of the spurs 

 leading up to Snowy Bluff, show some fine examples of columnar 

 structure in the rhyolite. One good example is shown on the 

 right bank of the river at the extremity of a spur at a point on the 

 mining track just below where it crosses from its descent on the 

 western side of the river. 



From a spur lower down the river, on the same side, some 

 sheer cliffs several hundreds of feet in height, showing again fine 

 columnar development, can be seen. The rock face overlooks a 

 tributary valley draining from Snowy Bluff, and is difficult to 

 approach. 



High up the Tamboritha mining track, to the west of the 

 Moroka Valley, numerous quartz geodes were strewn along either 

 side of the route. They evidently occur plentifully in a special 

 type of the rhyolite. Their radiating tongues of pink to white 

 chalcedonic quartz gave them an attractive star-shaped outline. 

 The whole of the top of the ridge traversed from the mining 

 track, south to Wellington, appears to be composed of rhyolite. 

 In places, especially near the top of the mining track, west of the 

 geode occurrence, a great development of white quartz is to be 

 noted. It appears to be a variety intermediate between 



