1883.] The Geology of Central Australia. 1125 
derlie them. What the thickness of the whole formation is, 
therefore, it is impossible to say. The thickness of the beds 
mentioned above is about 250 feet; in many places, however, 
some of the beds thin out and are wanting; this is notably the 
case with the fossiliferous limestone. 
Lake Eyre lies south of the center of this great zone of rocks. 
They extend westwards probably nearly 300 miles. Then they 
Sweep around the northern end of the lake and extend eastwards 
for about a hundred miles, as far as I have been able to ascertain. 
Circling around the northern boundary of the Jurassic beds and 
lying unconformably on them, where they overlap, is another 
series of rocks which varies greatly in character. In the north- 
west they consist principally of kaolin beds, sandstones and lime- 
stones. The kaolin beds are the best developed, and are un- 
doubtedly derived from the masses of eruptive felsites mentioned 
above. These beds flank the Musgrave and Everard ranges and 
extend north an unknown distance. 
The kaolin varies from a pure white, unctuous clay to gritty 
and indurated siliceous varieties of different colors. The finer 
inds are very abundant. One in particular, known colloquially 
as the “ Charlotte Waters’ meerschaum,” is a beautiful soft white 
variety. The Charlotte Waters telegraph station is built of it. 
Neither the kaolin nor the beds associated with them (sandstones 
and limestones) are fossiliferous, but eastwards they are continu- 
Ous with beds resembling the Jurassic lithologically, but contain- 
ing true Cretaceous fossils. So it is presumable that they belong 
to that age. To the north-east and east the Cretaceous beds ex- 
tend to the Gulf of Carpentaria and some distance into Queens- 
lan They consist here principally of sandstones and gypsifer- 
Ous marlites containing Ammonites, Belemnites, Trigonia and 
remains of Ichthyosaurus. 
outh-east of this great Mesozoic basin lies the immense basin 
of the Murray river, The latter is covered with Tertiary depos- 
its and is separated from the former by outcrops of the Cambrian 
rocks, The Mt. Poole and Mt. Browne range, about sixty miles 
South of Burke's grove at Innaminka, consists of these rocks and 
auriferous quartz veins are being worked there at present. Over the 
Cretaceous and Jurassic beds lie recent drifts and zolian deposits. 
fo y gr eater part of the continent, in fact, is covered with such 
“mations, and as they are so extensive and important, I will 
Write of them in detail. d 
