Page:Quarterly Journal of the Geological Society of London, vol. 35.djvu/37

Rh yielding Upper Silurian fossils, have led to this belief. But too much weight may have been perhaps attached to this negative evidence. In a group of strata at Tabberabbera, many of which are as indurated and slaty as any in the district, Middle Devonian fossils are met with.

I point out these doubts as to the propriety of considering all this area as Lower Silurian, or even Silurian; but provisionally I use these terms for description.

The apparent paucity of fossils is probably due to the slight examination which has yet been possible of an immense area of mountainous country, all of which is clothed with forest, and very much with dense and sometimes almost impenetrable scrubs.

(b) Metamorphic Crystalline Schists.—We find, occupying the central part of the Omeo plateau, and intimately connected with the last-mentioned strata, a great extent of crystalline schists. They may be defined as extending from the Dargo River to the Limestone River, in a direction east and west, and from the Painting Bange northward far beyond the limits of the district I am considering.

They do not, however, occupy exclusively the whole of this tract of country. Slaty and indurated rock masses, which I regard as Silurian, appear in places, as at Bindi, while other extensive areas are of granite, not belonging to the crystalline-schist series, and elsewhere are varieties of quartz-porphyries. At the Omeo Plains there is a wide extent of nodular argillaceous schists, which are connected with, but do not, as it seems to me, belong to the Omeo crystalline schists.

These latter form a complete series of varieties of mica-schist and gneiss, with subordinate varieties of quartz-schist, the extreme end of the series being, on the one hand, a fine-textured, glistening mica-schist, as at Swift's Creek, and, on the other, granitic gneiss or schistose granites, as, for instance, in the Dry-Hill Creek at Omeo. Many of these latter are, in hand specimens, undistinguishable from an ordinary ternary granite.

The connexion of these crystalline schists with the Silurian is clearly shown in many places. I subjoin a sketch section (fig. 2), which, I believe, exhibits tolerably clearly the position of the Omeo schists in the geological series. The section has been sketched from one constructed to scale from notes which I have prepared to illustrate a series of papers on the geological structure of North Gippsland.

In looking at the details of this section we see that the tilted and denuded Silurian strata appear from under the scarped edge of the Upper Palaeozoic "Iguana-Creek beds." They extend, as the section shows, across to the Dargo Biver, forming a mountainous country excavated into deep valleys and high steep ridges by the Wonan-