212 PROCEEDINGS OF SECTION C. 



microscopical fineness of grain. Such rocks as these approach 

 very closely to the definition of phyllite, and by that designation 

 I shall speak of them. Thus the phyllites illustrate the next 

 stage of structural alterations from the argillites to mica-schist. 



Such features as these are well shown in the valley of the Upper 

 Dargo River. In proceeding thence eastward towards Omeo, the 

 first change observable in the Silurian sediments is, that the 

 argillaceous beds become slightly corrugated, or show a wrinkled 

 surface on the glistening cleavage planes. Together with these 

 appearances there ai'e also numerous minute veins of quartz, which 

 either form partings or free fissures crossing the beds. At a still 

 further distance the beds have more or less the structure and 

 appearance of mica-schist ; then follows a wide band of gneiss- 

 ose beds, and finally there is reached a tract of holocrystalline 

 massive rocks which are usually of the chai-acter of the quartz 

 diorites. 



Crossing the area of the crystalline rocks of Omeo still further 

 to the eastward, the Silurian sediments are found much in their 

 normal condition in the valley of the Tambo River, near Tongeo. 

 They form the eastern side of the Bowen Mountains, which are 

 part of the Great Dividing Range between Bindi and Omeo. On 

 the falling ground from the Bowen Mountains towards Livingstone 

 Creek, argillites are increased either by phylites, or directly by 

 mica schist of fine grain. Somewhat further on, as for instance 

 in following the hills from Mount Cooke, towards the Hinnomunjie 

 morass, the beds are well marked varieties of nodular mica-schist, 

 either very micaceous or very quartzose, thus representing in their 

 alternations those of the argillites. 



A strong fault runs across this country from near the Tongeo 

 Gap towards the Mitta Mitta River, in a direction approximately 

 N. 30° W. It extends for many miles. On its south-western 

 side there are only intrusive plutonic rocks of the granite and 

 diorite groups. The mica-schists extend to the fault on its 

 north-eastern side, becoming more markedly micaceous when, at 

 the fault itself, they are brought into contact with the igneous 

 rocks. That this contact is not mei-ely proximity, due to faulting 

 becomes very evident when the district is examined. I have 

 elsewhere described this at length, and may refer to that description 

 for fuller particulars.* The line of contact is irregular by 

 reason of promontories of muscovite granite, which extend into 

 the mica-schists. Outlying masses of the same rock are to be 

 found at a distance of more than a mile within the schist area, 

 and dykes and dyke -like masses of igneous rock have penetrated 

 the schists, either passing between the beds, or in some cases 

 aci'oss them. The schists, for a considerable distance from the 

 fault are strongly filled with minute pale brown crystals of 



*Notea on certain Metamorphic and Plutonic rocks at Omeo. Trans. E. See, Victoria, 1887. 



