Page:Quarterly Journal of the Geological Society of London, vol. 35.djvu/35

Rh GEOLOGY OP FORTH G1PPSIAKD, VICTORIA. 9

Nowa Nowa, near Bindi, at the Reedy River (which is one of the feeders of the Buchan), and in other minor localities which need not be further specified. In the country between the upper waters of the Mitchell and Macallister rivers Silurian strata probably underlie the Upper Palaeozoic groups.

The strata which I regard as Silurian consist of alternating slates and sandstones, with rare bands of crystalline limestone in the upper part of the series. These have been tilted, folded, compressed, and subjected to influences which have produced alterations lying be- tween a schistose and a flinty structure. They have subsequently been extensively denuded before the deposition upon them of later formations. The strike of these strata naturally varies, owing to the many disturbing causes which have affected them. I have found some difficulty in determining the average direction of strike ; but, from the consideration of all the observations which I have been able to make throughout the district, I believe that the average strike will be found to lie between 35° to the west and 20° to the east of north. The dip appears usually to be between 60° and ver- tical, and varies rapidly ; but I am inclined to believe that it is more generally to the eastward than the westward, and would therefore indicate not only a general acute folding, but also a subsequent tilting over to the west.

I have observed in two localities, near Dargo Flat and Neoyang, where the contact with the granite has been laid bare by denuda- tion, that the strike has turned nearly east and west, the dip being both against and from the granite.

The largest Silurian area is situated, as I have said, between the Mitchell and Tambo rivers, and extends from the Great Dividing Range to near the sea-coast. Broadly viewed, it is a country of deep valleys and corresponding high and steep ridges, among which occasional outcrops of granite are to be found. These are usually in valleys, but also in some cases as mountains, such as Mount Baldhead. The Silurian mountains are in places capped with out- liers of Upper Palaeozoic strata, or with Tertiary volcanic outflows. Here are situated the alluvial gold-workings of the Crooked, Dargo, Wentworth, Tambo, and Nicholson rivers, of Merrijig and Boggy Creeks, of Shady Creek and the Haunted-Stream, and other places, and the quartz-mines of Grant, the Upper Dargo, Boggy Creek, and Deptford.

The second area, as to size, is, as I have said, east of the Snowy River. The country is one of steep and high mountains, gradually culminating in the chain known as the Coast Range. Their struc- ture is perhaps best seen at the Deddick River, and I shall refer to that as an illustration*. The general features are that the summits of the mountains are of highly inclined strata, usually much indu- rated, so that the slates are flinty and the sandstones quartzites. In many places the original structure of the rocks is almost oblite-

lalla, and Bonang, these being the native terms for the various localities through which it flows.
 * The Deddick River is also called, in parts of its course, the Tubbut, Jinigal-