HORN EXPEDITION — GENERAL rJEOLOHV. 65 



of extinct niouiid-sprinf:fs, as at Dalhousip, may bo explainod by tlie circunistanep 

 of a (liiiiinisIuHl .sup]>ly, in otlier words tliat tlif level of saturation lias fallen below 

 the level of discharge as a consefiuence of the desiccation of the tliniate since 

 Pliocene times. 



VI. — Desert Sandstone (Supra-Cretaceous). 



Geiwral Charactfrs. — The greatest thickness presented Ijy this formation, as 

 observtnl at Crown Point, was estimated at fifty feet ; it consists of three distinct 

 beds of about ecjual thickness. The topmost ))and is a breccia of Desert Hand- 

 stone fraij;ments cemented by secondary hyth'ated quartz ; the .same phenomenoii 

 was noted at Henbuiy on the Finke River and on the hill-tops about .Storm Cii'ek. 

 The other bands present the prevailint;' characteristics of the Desert Sandstone, 

 which is composed of sharp gr-ains of glassy quai'tz, varying much in size, cemented 

 by opaque white highly siliceous matter and more or le.ss stained red by oxide of 

 iron. 



No evidence of unconformal)ility between Upper Cretaceous and Desert 

 Sandstone was observable betw(!en Oodnadatta and the northern conlines of the 

 Cri^taceous area, though there is some reason for the opinion the lattei- overlaps the 

 former. AVitli one single exception the Desert Sandstone reposes on the Upper 

 Cretaceous, but at Heidnn-y a few small knolls of Desert Sandstone repose on 

 Ordovician limestone. The Ijase of the Desert Sandstone is never conglomeratic, 

 though pebbles of (piartz ami angular pieces of indurated shale were found at a 

 de[)th of ten feet Ix'low the summit of i[()unt Daniel. 



Pa/({'Oiif(>/(\i^iraI Featincs and Correlation* — Hitherto no fossils have ))een 

 recognised in the Deseit Sandstone within the ai(\i traversed, if we expect obscure 

 impressions jii'obably of twigs oi- wood. lUit the topmost stratum of the table- 

 topped hills, to the south of Oodnadatta and extending into the basins of Lakes 

 Torrens and (lairdnei', which has the structural peculiarities of the Desert Sand- 

 stone, except that it is rudely fissile, contains plant-impressions. And in i\w- 

 south-east part of the Lake Eyre basin extending to Lake Frome a similar tlora 

 occurs in cailjonaceous strata, which ;it the latter locality is associated with marine 

 fossils of Cretaceous age. A more particular account of thes<» discov(U-ies is now 

 submitted : — 



•' The siil)st.'ince of this sulj-chapter, undei- the title of " Plant-Bcariiitc .Strata in Ofiitral Australia," was read 

 Ijy one of us before the Royal So<'iety, S.A., 2Md July, 1889, liut the puhlio.ation of it was deferred peiuliiis; the 

 result of the bores in the Lei;,'h's Creel; coalfield, whieh have however no conr.eetion with the siibjec't now to be 

 dealt with. 



