38 



colour. The whole series is horizontally stratified, and covers the 

 primary rocks of the ranges to an altitude of about 400 feet above 

 the sea. From about three-fourths of the eastern side of the 

 range the country has been denuded deeply into the clay bed, 

 which constitutes the plain extending to Lake Eyre. A remnant 

 of the horizontal beds in places still clings to the face of the 

 range, and a few flat-topped hills in the j^lain attest the depth of 

 eroded strata. From Anna Creek to the Douglas the lower 

 rocks are occasionally exposed by the almost complete removal 

 of the sandstone and ironstone beds, but at Davenport Creek a 

 sudden uprising of the strata takes place and culminates in the 

 summit called Mount jNIargaret. This upraised ridge and the 

 mount itself rise clear above the horizontal beds which fringe 

 them. From Anna Creek to the Douglas the formation consisted 

 of quartzite (very dense), sandstones and slates, the whole 

 traversed by dykes of white felspar. Thin covering patches of 

 the flat bedded sandstone and ironstone occupy the hollows be- 

 tween the undulations. The ranges are almost bare of vegeta,tion, 

 and standing on one of the peaks nearly east of Mount Margaret 

 T could distinctly make out the strike and dip of the lower beds 

 and their relation to the horizontal ones of the tal)le lands. 

 Mount Margaret is near the centre of an area of great dislocation 

 and faulting. The southern ridge rises steeply from the eastward, 

 and up its face of 200 feet I counted thirteen beds of brown, 

 flne-grained, or compact quartzite intercalated with beds of 

 talcose or mica-slate. Tlie whole series dipping west at an angle 

 of about 50 deg. The creeks which originate north of Mount 

 Margaret run out eastward through gorges which give good 

 natural sections and show the lowest bed to be a thick bed of 

 conglomerate, formed of boulders of hornblendic, chloritic and 

 micaceous schist cemented together by lime. In the cliff" sec- 

 tions numerous caverns are seen, some large enough to contain 

 three or four horsemen. They seemed caused by the dislodg- 

 ing of a nest of boulders by water Altering out from the 

 sides of the gorge. Chloritic and talcose schists lie above this 

 bed, and are succeeded in turn by the brown quartzites and tal- 

 cose slates as disjDlayed in the southern spur. Numerous dykes 

 of granite containing very dittle mica or quartz seem to have 

 been the flrst disturber of the strata, while a second disturbiance 

 was afterwards caused by extensive eruptions of syenite 

 frequently so quartzose as to be termed a quartz-syenite. This, 

 quartz-syenite forms low hills about seven miles out on the 

 plain north-east of Mount Margaret, at the base of which are 

 some springs rising through the clay, whence the hill is termed 

 Spring Hill. North of Mount Margaret the swelling, of 

 which it is the culminating summit, again sinks down to the 



