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remain where they are and will not “ peter out ” when most wanted, as oil wells sometimes do* 
Their profitable development will depend upon research and business methods and not so much 
on wild-cat speculation. I consider them to be one of the greatest assets that Australia possesses, 
and the day of their very great importance may yet come. 
SECTION III. 
Notes on a Supposed Oil Occurence at Walcha, New South Wales. 
The town of Walcha is situated on the New England tableland some 200 miles due north 
from Sydney. The average height of the district above sea level is in excess of 3,000 feet. The 
town stands on highly folded and metamorphosed schists, which are regarded as belonging to the 
older Palaeozoic period and possibly of Silurian age. To the west a large area of granitic rocks 
runs northward to and across the Queensland border. Patches of granite, varying largely in 
area, frequently break through the cover of metamorphic rocks, more frequently indeed than is 
i ndicated on the geological maps at present. 
Lying more or less horizontally on the metamorphic rocks in places, are sheets of basalt, 
sometimes 200 to 300 feet in thickness and often showing well marked columnar structure. These 
are flows due to volcanic eruptions which were particularly active in many parts of Australia 
during the tertiary period. The sheets of lava have sometimes covered old depressions which 
were previously occupied by fresh water lakes or marshes, and the deposits laid down under such 
conditions, which have been largely removed by denudation elsewhere, have been protected and 
preserved by the overlying basaltic cover. These deposits consist of dark carbonaceous shales 
and clays, sands, blackened with humus and other carbonaceous matter and some lignite 
containing fragments of brittle, lignitic wood, sometimes so altered as to show the shiny, black, 
cleavage faces characteristic of the true coals. Prospecting for oil has been carried out by 
local people, and by misuse of the term “ oil ” for the lignitic beds and “ seepage ” for the 
outcrops, a hopeful atmosphere has been created around the venture. 
The particular area examined by myself lies at the head of the Tia Valley, 26 miles to the 
south-east of Walcha. Cappings of basalt encircle the valley at this point, sometimes extensively 
decomposed into red ochreous material. The valley floor is almost level, being broken only 
by low rises where outlying remnants of basalt still exist ; elsewhere the low lying area is underlain 
entirely by the lignitic beds which cover a fairly extensive area. They have been traced for 
four miles to the east, and pass to the south under the basaltic cover, appearing again south of 
the watershed at the head-waters of Lignite Creek. 
Five shallow pits have been sunk at the south-west end of the valley and have proved a 
thickness of about 20 feet of lignitic material. Since at the time of my visit the pits were filled 
with water owing to recent heavy rains, I could not ascertain the nature of the beds exposed in 
the pits, but it is certain that the 20 feet cannot be taken as the thickness of a bed of true 
lignite. The carbonaceous shales weather to a fine sticky clay containing fragments of woody 
matter, and this forms a cover which varies from 18 inches to 5 feet in thickness. Immediately 
under the basalt in places is a layer of copper blue earth due to decomposition of the basalt itself. 
Along the line of junction are numerous springs of fresh water. These, together with the water 
filling the pits, were perfectly clear and fresh and showed no signs whatever of free oil on their 
surfaces. It can safely be said that there is no evidence of free oil in this vicinity nor of any oil 
seepage, nor are they likely to occur. No doubt a little oil can be extracted from the carbonaceous 
matter present in these deposits by destructive distillation as it can from other brown coals, as well 
as oil shales and kerosene shales, but in this case, it could not be done profitably on a commercial 
scale. The development of the much richer and better situated kerosene shales of New South 
Wales has languished in a manner which is regrettable during recent years, so it is quite certain 
that the deposits in the Tia Valley will be of no commercial importance for many years to come. 
June 30th, 1925. 
ARTHUR WADE. 
By Authority : IT. J. Green. Government Printer. Melbourne. 
