44 



hills are met with. They probably belong to the same forma- 

 tion. The low hills of Ordovician age are readily distinguished 

 from these. 



In travelling up the Finke River, from Horseshoe Bend, 

 the Finke River sandstones are continuous to a spot a little- 

 north of Idracowra Station. One mile north-west of the 

 homestead red sandstone flagstones form the north bank of 

 the River Finke for half a mile or so. These flags probably 

 represent an earlier rock formation. A few miles farther 

 north-west, again, similar flagstones are seen near the southern- 

 edge of the Ordovicians. It is here the Finke River sand- 

 stones, etc., as a continuous formation, find their northern 

 boundary on the Finke, but they occur as sporadic hills in the 

 valleys, in and about the ranges, for many miles further to 

 the north and north-west. These are of the same description 

 as those already mentioned as occurring along the Alice 

 Springs track. Near Henbury Station a nest of these 

 hills occurs. Between Horseshoe Bend and Idracowra the 

 purple-shale beds belonging to this formation are much in 

 evidence; their prominence is due to a low anticline having 

 elevated the purple beds, the hills in places showing only a 

 thin capping of white sandstone upon the purple shale, but 

 they sink again near Idracowra. These purple shales are the 

 lowest visible beds in this formation. White sandstone beds 

 follow in ascending order, then calcareous sandstone bands 

 and pebble-bearing sandstones and thin bands of ironstone; 

 then yellow and purple sandstones. These latter appear to 

 mark the line between the Cretaceous shales and the Finke 

 River sandstone series. About this horizon green glauconitic 

 sandstones and shale bands succeed, in which J. J. East found 

 Lingula subovalis. 



The included boulders and pebbles in the sandstone beds 

 are very numerous and well-rounded, and principally com- 

 posed of quartz and quartzite. They represent the harder 

 rocks in the ranges to the north. The post-Ordovician con- 

 glomerate beds, noted later, that flank the South MacDonnell 

 probably furnished a large proportion of the pebbles. At 

 Crown Point these pebbles and boulders form conglomerate 

 beds in the sandstone varying from a few inches to several 

 feet in thickness, and they occur on inclined planes and at 

 varying angles of dip. The sandstone shows false-bedding, 

 in a marked degree, also. The boulders occasionally are up 

 to a couple of tons in weight. All are well waterworn. A 

 good example of the way the conglomerate occurs in the sand- 

 stone may be seen in the cliff and banks of a small creek where- 

 the telegraph line drops on to Paddy's Well plain, six miles 

 north of Old. Crown Point Station. There the conglomerate- 



