Geology of Warrandyte Gold field. 521 



ticularly at Fourth Hill, a long ridge forming the crown of the 

 main anticlinal fold of the district, along the axis of which 

 most of the principal quartz reefs occur. An erroneous impres- 

 sion is likely to be obtained that these coarse-grained rocks are 

 the predominant ones ; but a careful inspection of the country 

 and a glance at the mining dumps show that the shales and 

 sandstones are by far the most common. Dr. T. S. Hall (12, 

 p. 58) has referred to a somewhat similar instance at Castle- 

 niaine, although there is little accumulation of loose blocks in 

 the valleys at Warrandyte. The coarser-grained rocks how- 

 ever, where they form a moderate proportion of the strata, 

 largely determine the rate of denudation of the hills. 



The conglomerates and grits vary in thickness from a few 

 inches to about 12 feet. With one exception they cannot on 

 the surface be traced more than about 100 yards, and usually 

 less than that. In most cases they seem to pass rapidly into 

 sandstones and shales, both along their line of strike, and in 

 their vertical succession. Alternating sections are common. 

 The rocks vary from fine grits to conglomerates, containing 

 pebbles up to 3 or 4 inches in diameter. In the coarser rocks 

 the pebbles are w^ell rounded and water-worn. In the grits they 

 are angular, and appear to have travelled little distance. The 

 pebbles are of quartz, quartzite, sandstone, and flint or chert, 

 quartzites perhaps being as abundant as any rock. Most of 

 these rocks, as well as some sandstones and shales, are cal- 

 careous ; but much of the lime has been leached out. The 

 conglomerates are in places exceedingly tough ; and project 

 in boulders above the surface of the ground. Others are soft 

 and friable, and wotild not be noticeable except for artificial 

 sections. <.^uartz veins occur, but usually about ^ or ^ of an 

 inch thick, and in the hardest conglomerate are almost absent. 



The only conglomerate that can be traced any distance is one 

 seen in section in Whipstick Gully, near the Victory mine. It 

 is here abotit 12 feet thick, and is a tough, dense grey rock 

 when fresh. It differs from most conglomerates of the district 

 in having comparatively few, but always well-rounded, pebbles 

 set in a fine matrix. This, and its mode of weathering into 

 large boulders, enable it to be readily traced. It is found on 

 both sides of Whipstick Tiully and of Anderson's Creek. Its 



