2,7Z 



Section 6?), and elsewhere to the north and south, there appears a considerable 

 thickness of a coarse felspathic sandstone of a rather crumbly nature. This 

 resembles very closely the felspathic sandstone constituting the basal beds at 

 Aldgate, though ilmenite is not a feature of it. Unfortunately its relation with 

 the "Barossian" rocks forming the elevated block between the Meadows Creek 

 and Blackfellow's Creek is obscured by a belt half a mile wide of old valley 

 deposits, presumably in part a residual of Permo-Carboniferous glacio-fluvial 

 sedimentation. 



The "Barossian" rocks of the elevated block to which reference has just 

 been made are mainly gneisses. On the eastern side, more or less along the line 

 of Blackfellow's Creek itself, they are overlain unconformably by coarse ilmenite- 

 bearing pebble beds and arkose which constitute the base of a thick series of 

 slaty and calcareous beds and quartzite extending across the Mount Magnificent 

 Range towards Strathalbyn. There seems to be no doubt that these beds are the 

 lower members of the Adelaide Series. They were examined in detail as far as 

 available outcrops would allow across the range to Bull's Creek. 



The outcrop of the central "Barossian" massive opens out to the south and 

 contracts to the north. No definite outcrop was observed north of Section 253 

 (Kuitpo), where it is well exposed in the creek bed near an old ruined home- 

 stead. The ilmenitic basal bed is seen on Section 3412. What features of the 

 underlying strata are to be noted on Sections 246, 245, 251, 247, and 248 are 

 indicative of the close proximity to the surface of the gneissic rocks over the area. 



THE BAROSSIAN SERIES. 



These oldest rocks have been referred to by Dr. E. O. Teale.^^^ Where 

 he noted fresh exposures of them they were observed to "consist mainly of 

 siliceous schists, varying from quartz-schists to sericitic- and chloritic-quartz- 

 schists, with some phyllitic-schist. They appear to be pegmatised in places, but 

 fresh exposures are rare." 



A more extended examination on the Blackfellow's Creek side has now 

 revealed extensive areas of gneiss. On Section 90, they outcrop in a fresh 

 enough state for microscopical examination. There the foliation planes strike 

 N. 30° E. true and dip at 65° to the E.S.E. A very similar strike was noted 

 to be a general feature of the formation over a wide area. Three specimens 

 of gneiss collected at this locality have the following features : — 



A coarse Felspar-Quarts-Gneiss. This is an aplitic type without mica and of 

 coarse irregular texture. It consists principally of orthoclase, though quartz 

 is also abundant. Scattered grains of plagioclase are present amongst the smaller 

 material. 



Even-grained, aplitic and perthitic, Felspar-Quartz-Gneiss from the creek 

 bank near the mine shaft on Section 90. This is composed principally of an 

 orthoclase-microcline perthite. Plagioclase, answering to oligoclase, is present 

 in comparatively small amount, partly intergrown as perthite and partly free. The 

 quartzes are mostly small and rounded, embedded in allotriomorphic felspars and 

 present only in comparatively small quantity. The quartz shows strain features. A 

 few grains of zircon and a little leucoxene are present. 



Grey Zircon-Syenite-Gneiss from the main north-west to north-east trend- 

 ing tributary joining Blackfellow's Creek on Section 90. This is foliated in 

 fine-grained bands, occasionally giving place to strings of a coarse texture in 

 which felspar is prominent. Under the microscope the rock is seen to contain 

 very abundant orthoclase, a little oligoclase and quartz in small quantity only. 

 Biotite is distributed in very small fragments, and rarely distinct flakes of 

 muscovite appear. There is, however, a considerable amount of fine sericitic 



W Bull. No. 6, Dept. of Forestry, University of Adelaide, p. 7. 



