CHAPTER XXXI. 
THE EOLLING- DOWNS FOEMATION (LO'WEE CEETACEOUS). 
AETESIAN WELLS. 
As will be seen by tbe Geological Map, the “ Soiling Dowias Formation” covers 
an area which may be roughly stated at three-fourths of the total extent of the Colony. 
It extends westwards from the Palffiozoic ranges on the east coast, from near the heads 
of the MacIntyre in the south to the Palmer in the north. West of this line it occupies 
the whole of the Colony, save where it is unconformably overlaid by the Desert 
Sandstone, and where the Palaeozoic rocks of the Cloncurry, and of De Little, Cairn, 
and the Grey Eanges rise from beneath it like islands. Westward and southward it 
extends across South Australia into Western Australia and New South Wales. Except 
in Queensland, however, it appears to be covered to a considerable extent by Tertiary 
rocks. It marks the position of a sea which in Cretaceous times divided the Australian 
Continent into two islands. 
The Ipswich Coal Field seems to pass upward into the Foiling Downs Formation, 
although the junction has not yet been satisfactorily traced. To draw a definite lino 
between the Ipswich and the Bolling Downs Formations is quite impracticable, but the 
appearance of Belemnites and Ammonites, with other marine forms, in the latter, suffi- 
ciently marks the change from the plant-bearing beds of the former. 
' Everywhere in the North the Bolling Downs Formation lies directly, and of 
course unconformably, on schists and slates of undetermined ago, or on granite or 
gueiss,the Ipswich Formation being unrepresented. Tlie “ EollingDowns” is bj^ nomeans 
a mountain-forming formation. Generally, its decomposition forms a rich soil which is 
taken possession of by the nutritious “ Mitchell” and “ Blue” grasses, so Mghly favour- 
able to the rearing of sheep and cattle. The surface rises into a series of gentle undulations, 
not, however, of sufficient importance to disturb the idea of a dead level. Travelling 
over the “ Downs” becomes monotonous after a few days, the sun rising in the east and 
setting in the west on the horizon of an ocean-like idain. The watercourses which intersect 
It are dry for the greater part of the year, except for a few waterholes, and are so iU- 
defined that it is hard to tell in dry weather which way the water flows in wet. 
Each watercourse is marked by a straggling fringe of timber, while the rest of the plains 
are treeless. As the streams are of this character, it results naturally that they 
rarely cut through the soil, and consequently sections of the strata occur only at wide 
intervals. 
The monotony of ttie scenery is the direct result of a sameness of composition 
throughout the whole series. 
In announcing the discovery, in 1867, of a suite of fossils by Mr. W. P. Gordon, in 
Wollumbilla Creek,* the late Bev. W. B. Clarke t referred to the “ pale sandstones of 
the creek, and hard red conglomerates and quartzites from between Wollumbilla and the 
Biver Amby.” [The latter probably Desert Sandstone.] Subsequently Mr. Clarke + 
stated that the Wollumbilla fossils occurred in rounded, nodular, or concretionary 
boulders, imbedded in a brittle marl in the creeks, and on the downs, which ate covered 
* Wollumbilla Creek is crossed by the Western Railway, 294 miles from Brisbane, 
t Quart. Journ. Geol. Soc., xviii. (18()2), p. 245. 
t Recent Discoveries in Australia, p. 52. 
