Igneous Rocks. 205 



writer found in reddish-coloured sandstones and mudstoues in tJio 

 north of the area, no other fossils have been seen or recorded. Mr. 

 Chapman has kindly examined these plant remains for me. and 

 has referred them to Haliserites Dechenianus, (Toppei-t, a fossil 

 ■characteristic of his Tangilian division of Ihc Silui'ian, and which 

 is very abundant in the Tangilian beds at Wood's Point. The 

 presence of Haliserites, the occurrence of fossiliferous conglomerates 

 and the general lithology of these beds, all point to a close similarity 

 with the shallow water marine or estuarine beds near Wood's Point. 

 Tangilian mai-ine fossiliferous strata occur at Starvation creek and 

 McMahon's which are approximately on the continuation of the 

 same line of strike as the beds near Narbethong and Marysville. 

 The evidence at hand, therefore, although not conclusive, supports 

 the belief that the sediments to the north of the volcanics near 

 Narbethong are Tangilian, i.e.. Upper Silurian, in age. In the 

 Al>sence of fossils from the beds near Healesville nothing definite can 

 be said respecting their age. 



Locally, near the intrusions of granodiorite, the sediments have 

 been metamorphosed and changed to hornfels. Such alteration, 

 however, is never very extensive. 



Auriferous quartz veins traverse the sediments in places in this 

 Area, but none of them have been economically important. 



4. — Petrology. 

 A. Granodioritt. 



Granodiorite and granodiorite porphyry occur as small intru- 

 sions at several points around the periphery of the extrusive rocks. 

 The most important localities in which these rocks outcrop are 

 Malory's falls; the Maroondah aqueduct, north of Healesville; west 

 of the road from Healesville to Toolangi, near Meyers' falls; Nyoia 

 and in the ranges west of Narbethong. 



Malory's falls. — At Malory's falls at a height of about 2000 feet 

 above sea level, is found a rather coarse grained, occasionally 

 porphyritic, rock composed of quartz, felspar, biotite and garnet. 

 Numerous pits are developed on the weathered surface of the rock 

 due to the removal of the felspar. Biotite occurs in fine six-sided 

 lustrous plates. Euhedral crystals of pink garnet (almandine) are 

 fairly common. Examined microscopically, the rock is seen to Ije 

 rery similar to the granodiorite described from the Macedon area. 

 by Professor Skeats and Dr. Summers.^ It is a holocrystalline 



