132 THE VICTORIAN NATURALIST. 



intruded into the Silurian strata, altering these rocks considerably 

 along the contact. It is auriferous in parts, and from it has 

 probably been derived the gold that has been and is still being 

 found along Scotchman's Creek. At the present time a specially 

 interesting occurrence of gold can be seen in the Evans Reward 

 mine, on Backstairs Creek, a western branch of Scotchman's 

 Creek, where decomposed grano-diorite is being crushed from a 

 strip between 2 and 3 feet wide, yielding ^^ oz. of gold to the 

 ton of material. There is no trace of any vein or reef of quartz ; 

 the gold is simply distributed among the decomposed and dis- 

 integrating grains of felspar and quartz of the grano-diorite, 

 which lie between what appear to be two parallel fault planes or 

 master joints, and are partially bound together by infiltrated oxide 

 of iron, derived from the decomposition of the hornblende and 

 biotite (black mica) of the grano-diorite. 



The dacites join the grano-diorite close to the Warburton 

 railway station and stretch northwards across the Yarra, forming 

 the high mountain, Donna Buang, about 4,080 feet above sea 

 level, which overlooks Warburton from the N., as well as the 

 mass of ranges about the head waters of the Graceburn, Maroon- 

 dah (Watts), Acheron, Ligar and other streams. Beds of 

 volcanic ash occur at various places along the flanks of this great 

 volcanic mass, which has been referred to by Professor Gregory 

 — see "The Geology of Mt. Macedon, Victoria," Proc. Roy. Soc. 

 Vict., Vol. xiv. (N.S.), part ii., 1901 (1902) — as the stump of an 

 ancient volcano. The dacite shows well in railway and road 

 cuttings in the township of Warburton, and usually decomposes 

 into a red soil of good quality, supporting a splendid forest. 



The Lower Cainozoic (?) sediments can be best seen in some 

 old gold workings, now about 60 feet deep, on the southern slope 

 of Little Joe, a high point between Warburton and Warburton 

 West. Here the upper deposits are red and yellow clays, with 

 pebbles and angular fragments of indurated Silurian rocks ; the 

 lower ones are yellow and pink finely sandy clays. The latter 

 have probably been deposited in a shallow lake, while the former 

 appear to be of fluviatile origin, and to have been brought down 

 by a river into a rapidly shallowing lake, perhaps formed during 

 the dacite eruptions by the damming of some valley. They are 

 auriferous, and at this place have yielded a great deal of gold. 

 The upper beds are visible in railway cuttings between Warburton 

 and Warburton West. 



The old Yarra terraces can be seen in several places in the 

 valley, while the Recent alluvium forms the present flats of the 

 streams. 



There are many points of geological interest not mentioned 

 in these brief notes, but they could not be examined in the 

 very short time available during the excursion. 



