374 



mica developed in the mash as a consequence of dynamic crushing. Some 

 definite ilmenite is to be observed showing typical leucoxene change ; also traces 

 of hematite make their appearance sporadically. Small colourless zircons are 

 easily discernible. This rock has evidently been a zircon-syenite which has been 

 subjected to considerable dynamic force, and thereby sufifered crushing and 

 foliation. The ilmenite content is very distinct in the micro-slide, and as the 

 basal bed of the sedimentary formation unconformably overlying it is rich in 

 ilmenite grains, there appears to be every reason to couple the syenitic rock 

 with the Houghton magma described by Benson <^^^ and to regard the sedimentary 

 formation as the Adelaide Series. 



Whilst referring to this magma, it is interesting to note that a dioritic form 

 of the same was recently found by Mr. C. T. Madigan and myself to underlie 

 the ilmenitic conglomerate at the Grey Spur, which locality is adjacent to the 

 Innian Valley, about 20 miles to the south-west of the spot under present con- 

 sideration. Dr. Benson has reported it at Houghton, Aldgate, Normanville, and, 

 by inference, at Mount Compass. So that it is to be recognized as the dominant 

 feature of the "Barossian" Series and the back-bone of the Mount Lofty Ranges. 



THE ADELAIDE SERIES. 



The beds lying unconformably above the gneisses of Blackfellow's 

 Creek commence below as coarse arkose and pebble beds in which are 

 chunks two and three inches in diameter of solid ilmenite. The felspathic 

 ingredient has been much converted to sericite at the very base, but this 

 change is less and less marked above. The coarse material is found only 

 within 20 or 30 feet of the base, for it quickly passes upwards into a massive, 

 fine-grained, felspathic quartz rock, with just a little mica appearing now and 

 again and a faint ilmenite veining. In all, the beds of this character, exposed in this 

 area, must reach 200 feet in thickness. On Sections 90 and 289 of Kuitpo this 

 basal formation strikes N. 42° E. true and dips at 40° to the S.E. 



The overlying beds, which are fortunately fairly regularly disposed, were 

 examined along two lines of section as far as Bull's Creek. The bold ridge-line 

 of the Mount Magnificent Range is outlined by a strong and thick quartzite 

 horizon, the Mount Magnificent quartzite. Between the base of the series and this 

 horizon, slaty beds with at least one thin quartzite band were encountered, but the 

 outcrops were too poor for any connected description. In several places about 

 a mile south of Prospect Hill, hard resistant nodules of the underlying formation 

 of a sage-grey colour weathered out of the soil proved to be a tremolite rock. 

 A study of the microscope section suggests that they probably represent meta- 

 morphose dolomitic sediments. The quartzite of the Mount Magnificent Range 

 varies considerably in texture from bed to bed. Where most strongly developed 

 it was noted to be even-grained and moderately fine in texture but felspathic. 



On the down slopes to Bull's Creek, and overlying the above quartzite, 

 more shaly beds were met. These pass into calcareous types above. On the 

 line of section between Prospect Hill and Bull's Creek at its junction with 

 Hamilton Springs Creek, a calcareous bar is met at the lower end of Section 

 3281, Hundred of Kondoparinga. and again more definitely at the junction with 

 Hamilton Springs Creek. In that neighbourhood Bull's Creek evidently owes its 

 location to the existence of this easily eroded line of strata ; it is a consequent 

 stream following a line of easy erosion. At this point on Bull's Creek is met 

 a dove-grey marble composed almost entirely of calcite. There are also various 

 gradations to less pure forms, in some of which brown biotite enters. 



(5) Trans. Roy. Soc. S. Austr., xxxiii., 1909, p. 101. 



