251 



so inclined that they can be examined to great advantage, thanks, 

 to the quartzite cappings. 



It was underneath these bluff-shaped headlands of quartzite 

 that I noticed fragments of fossils amongst the talus, and on 

 climbing-up under one of the bluffs, I discovered some hundreds 

 of feet thick of fossiliferous limestone in thin beds, with inter- 

 calated dark-green shales. The limestone was almost wholly 

 composed of fossil shells. I believe they may be had underneath 

 any of the bluffs, and for a distance of 15 or 20 miles without a 

 break. I also found fossils of the same age at the head of both 

 the Walker and Petermann Creeks, which have their commence- 

 ment on the top of anticlinal folds. The quartzite has been 

 denuded sufficiently to expose the shales and limestones, which 

 have eroded faster than the quartzite sides, and thus a valley has 

 been formed. 



A few miles to the west of Mareena Bluff Pass a fault appears 

 on the south side of this range, and exposes a headland of quart- 

 zite 1,000 feet thick, horizontally bedded. Wherever this forma- 

 tion is met with the cleavage is most perfect, and where the 

 sandstone remains unaltered, flag-stones of any size may be had. 



It would appear that symmetry is the order throughout Central 

 Australian, if not Australian rocks generally. Generalising may 

 be more safely dealt in than in most parts of the world. How 

 regular are the Cretaceous clays and Tertiary rocks overlying 

 them. The Ooraminna (Devonian 1) Sandstone is recognisable 

 at a moment when once its characteristics are known. The anti- 

 clinal and synclinal foldings of the Silurian formation maintain 

 such good parallels, that when several sections across them are 

 taken, even a few insignificant outcrops appearing above the 

 recent wind-drift sand, connect without fail the lines of folding. 

 The chief upheaval in Central Australia occurred towards, if not 

 at, the close of the Silurian epoch. It was then that the 

 MacDonnell Ranges assumed their general present shape, and the 

 Upper Finke Basin took on much of its present form. In the 

 synclinal fold, in which Tempo Downs Station stands, was next 

 deposited a rock at least 2,000 feet thick, described as 



Devonian — (1) Mudstone and (2) Ooraminna Sandstone, 



on tlie top of which, and conforming to it, was laid at least 

 2,000 feet of sandstone — the middle stratum may be described 

 as a highly ferruginous fine-grained sandstone, and the present 

 uppermost formation a red friable coarse-grained sandstone ; 

 sometimes white and feldspathose. It does not conform to the 

 Silurian rocks, and has been only subjected to slight longitudinal 

 pressure in comparison with the Silurian. It has, however, taken 



