264 N. M. Junner: 



3.— Upper Silurian Sediments. 



The basal beds of the Healesville area are a folded series of f airly 

 shallow water marine sediments, consisting chiefly of sandstones 

 and shales. Two fossiliferous conglomerates were found by the 

 Avriter near Narbethong, one on either side of the main road from 

 Healesville to Marysville. The western conglomerate was seen in 

 densely overgrown country, at a point about one and a-l^alf miles 

 east of the above-mentioned road, and about two miles from St. 

 Fillans. The conglomerate outcrops on a low ridge trending 

 approximately north and south, and is well jointed. It dips east 

 at about 70° and strikes about north and south, and contains 

 numerous poorly preserved fossils. The pebbles are mostly rounded 

 and sub-angular in shape, and consist almost entirely of sedi- 

 mentary rocks, vein quartz and quartzite being most common, and 

 chert and sandstone relatively uncommon. 



The eastern conglomerate is visible along the now disused road 

 from Narbethong to Marysville. It consists of exactly the same 

 types of pebbles as occur in the w^estern conglomerate, and contains 

 casts of fossils, chiefly corals and crinoid stems. The direction of 

 dip of the conglomerate was not determinate, but the sediment* 

 near by are west dipping, and presumably the conglomerate also 

 dips in this direction. It seems likely, from the structure of this 

 portion of the area and from the lithological similarity of the two 

 conglomerates, that they are on the same stratigraphical horizon. 

 The abundant pebbles of milky vein quartz are interesting, suggest- 

 ing the occurrence in Victoria of quartz veins, possibly auriferous, 

 pre-Upper Silurian in age. 



The Silurian sediments at, and to the east of Melbourne, strike 

 fairly consistently east of north. Near Healesville, however, the 

 beds swing round and the strike changes to the west of north, and 

 this direction is maintained as far east as Wood's Point. In 

 Healesville township the strata trends N. 20o W. approximately, 

 and dip about 70o to the west. In the northern portion of the area, 

 near Narbethong and Marysville,, the average strike is between 20<^ 

 and 30o west of north. No explanation is suggested for this change 

 of strike. Clearly the effect is regional and no explanation, involv- 

 ing local causes, e.g., the effect of the intrusion of the igneous rocks, 

 faulting or cross-folding can be valid. 



The precise age of these beds is doubtful. Fossils are very rare, 

 and with the exception of the poorly preserved fossils in the above- 

 mentioned conglomerates, and certain plant remains which the 



