^U E. 0. Teale: 



therefore, that the diabases and cherts of the Howqua belong to the 

 Heathcotian series, and must be regarded as Cambrian. Whether 

 .also some of the adjoining sediments are to be included in this 

 series must at present be left an open question. 



6. — The Upper Palaeozoic Rocks. 



Ihe present investigation was principally concerned with the 

 relationships of the older rocks, but soine of the later geology is 

 not without interest, and as rocks of this age are found in the 

 northern portion of the area under consideration, where they come 

 into contact with the diabase, a little time was devoted to roughly 



• demarking their boundaries and noting their main features. The 

 .rocks of this series fall into the following groups : — 



A. — Devonian. 



1. Dacite, porphyry, 



2. Granodiorite. 



3. Diorite. 



B. — The Lower Carboniferous. 



1. Basal conglomerates. 



2. Rhyolite. 



3. Conglomerates. 



4. Sandstones. 



5. Purple shales 



1. Dacite Porphi/nj. — This rock covers a considerable tract of 

 'Counti-y between Mount Tirabertop and the Howqua, and extends 



■ easterly towards the Buller Creek, where it gives place to Lower 

 Palaeozoic strata. It is also found to the north outside the region 



■ of this map on the fall towards Merrijig. Rock of this nature is 

 widely distributed in the King River Valley, as indicated by 

 Kitson.i2 In both localities it underlies the basal conglomerates 



■ of the Lower Carboniferous beds, in which pebbles of the porphyry 

 are not uncommon. In the Howqua area this feature was noted in 

 the Timbertop conglomerates. Professor Skeats^ has referred to the 

 King River porphyry as related to the Dacites. In hand specimens 

 the rock has a general dark colour, on account of a dark, fine- 

 grained base. It inclines to red, where oxidized and weathered. 

 Phenocrysts of felspar and quartz are abundant, the former pre- 

 dominating, and show up on the dark base, imparting a typical 

 porphyritic appearance. Garnets are frequently recognizable. 

 Under the microscope in thin sections chemical alteration in all 

 the specimens examined has proceeded too far for satisfactory 



• determination. 



