17 
worked out in detail, though from a brief inspection it may be not altogether unfavorable, some 
evidence of folding accompanied by faulting being observable in the underlying Mesozoic beds. 
Some slight evidence of oil and gas, though not seen by myself, were reported by the drillers from 
the carbonaceous beds passed through, and these are confirmed with caution by Mr. Saint Smith. 
Some of the oil may have percolated into the hole from, the drilling plant. For some time power 
was obtained from a motor tractor which is still standing near the borehole, the fuel being Texas 
fuel kerosene. I have proved conclusively, in more than one instance in working in oilfields, 
that oil which inevitably gets spilled and scattered around on the surface in such circumstances, 
and especially where the underlying beds are of a porous nature, will be carried to considerable 
distances both laterally and below the surface by percolating water. It would be surprising if 
some of this oil were not carried along to the walls of the borehole and, trickling down outside the 
casing, make its appearance in the sludge at the bottom. It would be interesting to discover, 
if possible, whether the percentage of oil noted in some of these borings increased after heavy 
rains, some time being allowed for migration to take place. However, there is no reason to suppose 
that some of these showings are not. due to the presence of small quantities of oil associated with 
carbonaceous strata. The carbon-ratios of the coals present in these beds in the neighbouring 
Ipswich coalfield average around 70, which is too high for the expectation of commercial supplies 
of oil. Moreover, this series has been well explored by borings and shafts for coal, and these have 
revealed no evidence of the existence of oil in the strata. Oil finding is not an easy business. 
Much time and care must be spent on the careful study of strata and structural conditions before 
a site for a hole is selected. I do not think that oil will be found in Queensland by picking a site 
more or less at haphazard and boring upon it. Better sites can be picked than that at Wolston, 
which, in my opinion, is not so located as to be likely to prove successful. 
While examining the shales in the Cement Company’s quarry it occurred to me that they 
might yield some oil on distillation. I suggested to the manager that they should be tested. 
Similar shales have proved on examination to be quite good oil shales. 
V. THE COUNTRY NORTH OF THE RAILWAY LINE BETWEEN MILES AND 
ROMA. 
A. Stratigraphical Geology. 
In dealing with this section of Queensland, we can include also the area between Longreach 
and Isisford, in which the Ruthven bore is situated, since it is underlain by the Walloon strata, 
which constitute the most promising ground so far as oil prospects are concerned. In a general 
way the geology of this region is fairly simple. West of the Bunya Mountains, which run in a 
northerly direction a few miles to the E. of Dalby, the Walloon series outcrop over a strip of country 
about 50 miles in width, striking slightly N. of W. In the neighbourhood of Mitchell the outcrop 
swings around and takes on a more northerly direction, passing to the eastward of Blackall and 
Tambo, and crossing the Central Railway of Queensland near Jericho. The southern edge of the 
Walloons runs almost parallel with the Western Railway from Miles to Mitchell, a few miles to the 
N. of the line. The beds dip gently in southerly or south-westerly directions, and are overlain 
to the S. and W., apparently conformably, by the Cretaceous Marine series, above which the 
Cretaceo-Tertiary lies with marked discordancy of junction. Below the Walloon series lies the 
Bundamba sandstones, the basal conglomerate of which again appears to rest conformably upon 
the Triassic coal measures of the Tpswich series. A basal conglomerate, however, is a suspicious 
feature. In comparatively flat lying strata an unconformity may be present, though hard to 
distinguish. The Bundamba sandstone series constitutes another belt of outcrops which runs 
round the inner side of the reentrant angle formed by the Walloons. The only geological series 
with which we need to interest ourselves is the Walloon series, for it is from this series that the best 
evidences of the existence of oil and gas have been obtained in Queensland. (See map.) Dr. 
Jensen spent eighteen months doing reconnaissance work in this area when on the staff of the 
Queensland Geological Survey, and prepared a report and geological maps (unpublished). At 
the time of writing I have not seen the report, but some notes have been published independently. 
He estimates the thickness of the Walloon series north of Roma at 5,000 feet, and gives the 
following subdivisions of the Strata'' : - 
"Upper . . Shales and sandstones with minor inferior coal seams. Fels- 
pathic shales and carbonaceous beds interlaminated. — Orallo 
coal measures. 
Middle . . Sandstone. 
Walloon Series . . \ Calcareous sandstone. 
Thick sandstone. 
Lower . . Highly calcareous fresh water formation consisting of limestones. 
shales, calcareous sandstones, coals, and kerosene shales. 
Basal . . Felspathic sandstone. 
* .Tensen, Dr. H. I. ” Some Notes on the Permo-Carboniferous nml Overlyimr Systems in Central Queensland.”— Proc. of the Linn. Soc. of NSW 
vol. XLVIf, pt.2, 1923,’ pp. 153-158.. 
