288 H. S. Summers: 



III. — The Geologicai. Sequence. 



Tho rocks of this area may be divided into four groups. (A) 

 A S;eries of sedimentary rocks showinc: considerable contact meta^ 

 niorphism and probably of Silurian age. (B) Igneous rocks of 

 acid to sub-acid composition intruded into the silurian series 

 and Devonian in age. (C) Conglomerates occupying portions of 

 the valleys of Wild Dog Creek, Back Creek, and the Broken 

 River, probably of glacial origin, and of uncertain age. (D) 

 Recent alluvial deposits along the course of the streams. 



(A). — 71ie Silurian Rocks. 



The sedimentary series consist of indurated mudstones, shales, 

 slates, qviartzites, hornfels, etc., the alteration being due to the 

 intrusion of the granites and porphyries. Tlie s^trike of the'rocks 

 is very irregular, but still seems to have a general northerly 

 direction. So far no fossils have been found in these beds, but 

 there is little doubt that they are silurian in age, as they occur 

 on the same line as the fossiliferous sandstorues of silurian age 

 occurring at the Reef Hills, Benalla., and the silurian limestones 

 of Loyola, near Mansfield. 



Acid apophyses from the granite are to be se^en intrusive into 

 the sediments near the contact. The strata are much jointed 

 and faulted, a.nd show considerable contact metamorphism, most 

 of the rocks showing the presence of mica and other secondary 

 minerals. In the bed of Back Creek, about two and a-half miles 

 above its junction with the Broken River, a sharp junction be- 

 tween the sedimentary and igneous rocks is seen, and sections 

 show that the contact rock is a typical hornfels consisting of 

 granular c[uartz, with a considerable amount of biotite. 



(B). — Tlie lijiieou'i Rocl-s. 



Three distinct types of acid igneous n)cks occur, which may ue 

 provisionally called granite, granite porph^Tv and quartz por- 

 phyry. 



Tho granite is only found at tlie lower levels along the river 

 bed at ?bout f^OOft. above sea level. On the eastern side 

 of tlio river silurian rocks containing acid veins are met with at 



