i 
4 
i 
1883.] The Geology of Central Australia. IIIQ 
deposits are Tertiary, and sweep around the eastern side from 
north to south, becoming more recent to the southward. Mt. 
Gambier and Mt. Schenck are volcanic cones which are situated 
near the southern limit of this disturbance. On the south side of 
the continent raised beaches are common, but are of limited ex- 
tent. The great central depression, is, like the Saharan desert, of 
Mesozoic age. Its limits are as yet not strictly defined. Meso- 
zoic fossils have been found on the east side all around the Gulf 
of Carpentaria, and I have found Jurassic fossils i» situ 300 miles 
west of the overland telegraph line. Covering the Mesozoic 
beds in the interior are eolian deposits and drifts. On the north 
coast the Palæozoic rocks outcrop again and are overlaid uncon- 
formably by Mesozoic rocks. Such is the general structure of 
the continent. 
The region which I intend to discuss especially is that lying 
between the south parallels 22° and 30°, and the meridians I 30° 
and 140°. 
The country contained within these limits comprises very 
nearly the known limits of the great central basin. How much 
farther it extends to the westward is a matter of doubt. If a ver- 
tical east and west section could be cut through this basin from 
the eastern cordillera across Lake Eyre and through the Peake 
Tange, the approximate position of the rocks would be as seen in 
the diagram 
ic. aa G, granite; A—A, Archæan schists; ad, Archzean and Silurian 
schist ya eyonian and Pa. C, Cretaceous; J, Jurassic; 4, me aay 
cordillera, ő, e range; c’, Lake Eyre basin. r, inao of springs. 
Now if a section were cut in a like manner through the Peake 
range on the east, in a north-westerly direction through the Mus- 
Stave range, we should have a section as seen in Fig. 2: 
Fic, 2. G-G, ‘granite; A-4, Archean, 17 Jurassic; C, Cretaceous; 4; age 
grave range; 6, Peake range; x, outcrop of springs. 
The Musgrave ranges at their base are about 3000 feet er 
the level of the sea; the Peake range 800 feet; Lake Eyre 3 
