48 HORN EXPEDITION — GENERAL GEOLOGY. 



Ordovician conglomerate) as far north as the northern edge of the Finke River 

 Gorge as Ordovician. To what system the strata, that lie between this point and 

 Mount Sonder, belong we have no paheontological evidence to show. Owing to 

 the absence, however, of any signs of unconformability, we are of opinion that 

 they belong to the Ordovician System. There does not appear to be a great thick- 

 ness of strata on the south of Mount Sonder, as an inlier of gneissic granite 

 belonging to the Pre-Candjrian system is visible in the valley of the Davenport. 

 The rocks composing Mount Sonder and the low hills to the south consist of 

 quartzite, micaceous slates, and dolomitic limestone highly altered by the earth 

 movements, which seem to have been greatest here, and to have decreased in force 

 southwards. For this reason these rocks appear more altered than the typical 

 Ordovician rocks further south. We therefore cannot adopt Mr. Brown's classiti- 

 cation, because we have undeniable evidence of the Post-Ordovician age of one 

 part and of the Ordo\ician age of another, and lastly, because no reliable evidence 

 has been furnished of the Cambrian age of the remainder. Rocks of Cambrian 

 age constitute a large part of the Flinders Range, being certainly known to be 

 developed as far north as the Ajax Mine, between Beltana and Leigh's Creek, 

 where fossils similar to those found at Parachilna, Blinman, and other localities 

 in the Flinders Range, and described V)y Mr. R. Etheridge, Junr., have been 

 discovered. 



In 1894 Mr. Chewings (xv., p. 198) pointed out that annelid burrows are 

 present in the quartzites on the north side of Mereenie Bluff', and considers that 

 these rocks may be Cambrian. Similar annelid burrows were found by us in a 

 quartzite range, which appears to be an eastern extension of that spoken of by Mr. 

 Chewings. Some of the quartzite yielded to us other fossils, which fix its age as 

 Ordovician, and no doubt determine the age of the ridge referred to by Mr. 

 Chewings to be also Ordovician. In the atxme paper Mr. Chewings includes under 

 his heading Cambrian and Pre-Cambrian (1) the locks occuring in the valley of the 

 Davenport. Our reasons against such a view have just been given. 



In 1889 Mr. Brown (ix., p. 2) described the occurrence in the vicinity of 

 Mount Burrell of limestone with Hinty veins, quartzite, sandstone, and slates, 

 which he judged, basing his conclusions on lithological evidence, to be of the same 

 age as his so-called Silurian rocks of Anna Creek and Finnis Springs. These 

 latter bear every appearance of being northern inliers of the series of rocks, which 

 constitute a great portion of the Flinders Range, and which, at least as far north 

 as the Ajax Mine, have bet^n lately proved on palseontological evidence to be 

 Cambrian. There is no doubt that the Mount Burrell strata belong to the 



