56 HORN EXPEDITION GENERAL GEOLOGY. 



from three to four lumdrod feet high. The dip of this .sandstone varies from 

 G° to 8° on the nortli and south faces of the range, while about its centre the 

 dip changes, within the distance of half a mile, from 4° S.S.W. to 4° N.N.E. On 

 the summit of the northern escarpment the sandstone exhibits well-marked false 

 or current bedding, and tlie surfaces of the strata are ripple-mai-ked. This sand- 

 stone, which as a rule is fairly indurated and often approaches a quartzite, in other 

 places is of a white friable felspathic nature, indurated in places by secondary 

 silica. No fossils were discovered in this sandstone. Underlying this is a 

 yellowish thinly-bedded indurated mudstone, with more or less perfect cubes on 

 the weathered surfaces, which may represent pseudomorphs after some mineral, 

 probably rock .salt. The cubes vaiy from about an eighth of an inch to over half 

 an inch in diameter, the faces being concave. Underlying this latter rock quite 

 conformably are the fossiliferous limestones, which have yielded a small number 

 of Ordovician fossils. This limestone varies much in character when traced in the 

 direction of its strike for any distance. It is, however, always very argillaceous, 

 and varies from a grey to a yelluw and very often red colour. 



On the north side of Levi Range it dips at an angle of 14° S.S.E., and appears 

 to be quite conformable to the sandstone of the range. It has yielded numerous 

 specimens of Orthoceras and Endoceras, besides many specimens of RapJiistoma 

 brownii. The same series of rocks are to be made out to the west of Levi Range. 

 In the George Gill Range the sandstone has most of the characters exhibited by 

 the same rock in Levi Range, with the addition of a finely-bedded structure, well 

 seen in Martin's Pass. 



The uppermost zone is very rich in Orthis leviensis, while below come beds 

 enormously rich in Trilobite fragments. Quartzites underlie these limestones on 

 the north, the uppermost strata being apparently unfossiliferous. They dip at 14° 

 (about) in a S.S.W. direction, and are succeeded a little further north by fossili- 

 ferous quartzites dipping 17° S.S.E. The total thickness of Ordovician strata 

 between Levi Range and the point to the north of it, where the dip becomes 

 reversed about three-and-three-quarter miles north of Camp 25 on the bank of 

 Petermann Creek, is 7000 feet. 



At the top of the series are 560 feet of red sandstone, exhibiting current- 

 bedding and ripple-marks. Levi and George Gill Ranges are composed entirely of 

 this rock. Below this come 440 feet of yellow and grey mudstones and earthly 

 limestones and yellow and red argillaceous limestones, in the lowest beds of which 

 the majority of the fossils have l)een found. Lastly, below the limestones there are 



