CRETACEOUS ROCKS OE STEW SOUTH WALES. 
347 
when struct, and breaks with a conchotclal fracture. The prolonged 
heat of the sun followed by rapid cooling— owing to sudden thunder- 
storms and the frosts of winter — causes the larger beds to break up 
rapidly, and consequently it is rare to see an outcrop of solid beds, 
the hilltops being covered with a more or less rounded shingle. 
Evidences of the agency of thermal springs in these Upper 
Cretaceous rocks are frequent. At the Peak (Mount Stuart Ranges) 
ancient springs have left mounds of curiously banded limomte ; 
showing that many of them contained ferruginous solutions— indeed, 
the Upper Cretaceous rocks of this district are characterised by the 
occurrence of considerable quantities of iron oxide. 
Near the top of the Desert Sandstone occurs a thin bed (about 
3 inches in thickness) of conglomerate, the pebbles of which are of 
every conceivable colour, and the weathering of this conglomerate has 
resulted, in places, in the hillsides being strewn with highly polished 
pebbles of white and pink quartz, banded agates and chalcedony, 
jasper, carnelian, &c. The highly polished surfaces of these pebbles 
are probably due to the action of the wind and sand. Considerable 
numbers of these pebbles were seen at Yandaminta, about twenty 
miles west of Mount Poole. From the northern end of the Waratta 
Ranges to the Queensland border, the country consists almost entirely 
of Upper Cretaceous rocks (Desert Sandstones), and, generally speaking, 
it may he said that the Lower Cretaceous or Rolling Downs formation 
does not show at the surface over this district, being covered by either 
Upper Cretaceous or Pleistocene deposits of greater or less extent. 
In the spoil heaps of the wells, however, which have been sunk by 
many of the squatters, are to be seen characteristic blue clays and 
sandy shales with Belemnites , Maccoyella reflect a , 31. corbiensis ; also a 
very large bivalve, which Mr. Robert Etheridge, Junr., believes to be 
new', and a univalve which, according to the same authority, belongs 
to the genus Bapana. I also obtained a portion of the stem of a tree- 
fern (not yet determined) from the Upper Cretaceous rocks of Mount 
Stuart. 
One of the most interesting features of this district is the occur- 
rence, at Mount Browne and at Tibooburra, of auriferous drifts of 
Cretaceous age. This occurrence was, I think, first noticed by the 
late Mr. C. S. Wilkinson.* At the western end of Mount Browne, a 
rounded quartz pebble drift which has proved to be highly auriferous, 
and has been extensively w r orked on a small rise known as Billygoat 
Hill, dips suddenly beneath the level of the Upper Cretaceous Sand- 
stones which surround the Mount Browne Range. This quartz pebble 
drift takes its rise in the Mount Browne Range (Upper Silurian) 
somewhere near the Eour-mile Diggings, and it trends, with a gradual 
fall, in a more or less south-westerly direction for about four miles to 
Billygoat Hill, on the top of which the drift is seen to be about 3 
or 4 feet in thickness, lying on rather decomposed slate rocks. 
Erorn here it is evident that the old Cretaceous creek or river fell over 
a slate cliff, for at a distance of little more than 100 yards west the 
drift has been followed to a depth of 240 feet in the Mount Browne 
Gold-Mining Company’s shaft, operations in which were discontinued 
owing chiefly to the strong body of water met with. 
* Ann. Eept. Dept, of Mines, 1884, p. 137 ; and Records Geol. Sur. N.S.W., vol. i., 
part i., 1889. 
