48 



beds reposed upon conglomeratic sandstone beds. They, and 

 others, have noted the occurrence of pebbles, sometimes in 

 layers, in the "upper" red sandstone beds of the Krichauff 

 and other similar ranges. The same beds, with included 

 pebbles, form the bed of Ellery Creek between the Krichauff 

 and MacDonnell Ranges. Tate and Watt failed to discover 

 unconformity between this red sandstone series and the 

 Ordovician sandstones, limestones, and quartzites on which 

 the red sandstone reposes. They discovered Ordovician fossils 

 in the boulders of the post-Ordovician conglomerate, and 

 rightly deduced that they must be younger than Ordovician, 

 but they included the upper red sandstone beds in their 

 Ordovician, as they also did the Cambrian. Mr. Brown's 

 former reading of the Ooraminna sandstone — which is litho- 

 logically very similar to Krichauff Range and Ellery Creek 

 sandstone — was "probably Devonian," but in 1897 he included 

 it in his Jurassic ( ?). The author's reasons for separating the 

 two are already stated. Where, then, are we to place the 

 Missionary red sandstone beds ? The post-Ordovician con- 

 glomerate reposes upon them and gradually merges into them 

 without any apparent unconformity. Probably they belong 

 to one and the same formation, and pending further informa- 

 tion the author suggests they be included in post-Ordovician. 

 The discovery of a supposed cast of Isoarca in the sandstone 

 from Deep Well by Tate and Watt lends some little weight 

 towards their classification, but the sandstones there do not 

 resemble the Ellery Creek sandstone in any marked degree; 

 its mode of weathering resembles the Ordovician sandstone. 

 The discovery of annelide burrows in the Deep Well sand- 

 stones, and also in the Ooraminna sandstones, by the author 

 proves little one way or the other. These worm tracks are 

 very common in the Ordovician quartzites. It is also possible 

 that either the Ooraminna or Deep Well (or both) sandstones 

 are older than the Missionary sandstones, notwithstanding 

 any lithological similarity they may possess. Good sections of 

 the Ordovician and Missionary (post-Ordovician) series are 

 seen between Parkes Pass and Hermannsburg, on the Finke. 

 The Ordovicians are there thrown into sharp folds; the post- 

 Ordovicians are more gently inclined. The upper series, 

 which lie within the folds of the lower, are unfortunately 

 worn back, and the actual contact is covered with sand and 

 loam. 



Ordovician. 



The Ordovician system is well represented, in the 

 MacDonnell and other ranges to the south. The rocks are 

 composed of quartzites, sandstones, shales, limestones, etc., 

 as seen in the South MacDonnell, in Gardiner Range, on the 



