Page:Quarterly Journal of the Geological Society of London, vol. 35.djvu/63

Rh for this paper; but I may remark that my inquiries into the source from which the alluvial gold has been derived have, so far, shown that the auriferous character of the formations will have to be extended from the Silurian to the very highest Palæozoic groups with which we are here acquainted.

At Tabberabbera alluvial gold is worked where the "bed-rock" is Middle Devonian and the overlying strata Upper Devonian. At the Lower Mitchell River the whole of the strata are of the latter age. At lower Boggy Creek the bed-rock is quartz-porphyry overlain by Upper Devonian; but in this instance, as I have indicated elsewhere, the gold may have been derived from the detritus of the Silurian hills higher up the stream. At Maximilian Creek the lowest strata of the upper part of its course are probably Middle Devonian overlain by Upper Devonian, and in the lower part entirely the latter. My inquiries are at present not sufficiently advanced to enable me to speak decidedly; but, so far as they go, the conclusion seems very probable that the gold has been derived from the narrow quartz veins of the Middle Devonian shales, slates, and quartzites, or from the quartz-conglomerates of the Upper Devonian, which have certainly been derived from older and probably auriferous strata, or from the narrow quartz veins which here also intersect the conglomerate and sandstone. A fragment of quartz containing gold has been given to me which is said to have been taken from such a quartz vein in the Iguana-Creek beds of Maximilian Creek. If this can be satisfactorily substantiated great light will be thrown on the subject. I hope before long to be able to seriously attack this important question.

In the preceding pages I have attempted to give, as shortly and as clearly as I could, an account of the physical geography and geology of North Gippsland, so far as my inquiries have made me acquainted with the subject. I may briefly sum up the conclusions which it seems to me may be arrived at, and which I believe to be warranted by the facts stated.

In glancing backwards through the dim geologic ages the earliest record of the past which we can discern is the great Silurian series. Whatever formations of prior date there may have been, on which the "35,000 feet" of Silurian slates and sandstones reposed, no trace whatever, it would seem, now remains of them. The natural forces (dynamical, hydro-plutonic, whatever they may be termed) which compressed and folded the strata, which caused them to be metamorphosed, partially absorbed, or even invaded by the granites, no doubt also completely obliterated all those older rock masses on which the Silurian reposed, and from the wearing of which those Silurian strata were formed.