100 PROCEEDINGS OF THE ROYAL SOCIETY OF QUEENSLAND. 
Although correlation on lithological grounds is generally insufficient, 
such a close chemical comparison between the two limestones suggests 
that the Petrie Series may be equivalent, at least in part, to the Silkstone 
Series. This fits in with all the palaeontological evidence and other 
lithological evidence from the Petrie Series, which points definitely to an 
age later than that of the Redbank Plains Series. 
The rock, itself, is a somewhat chalky, non-crystalline, dolomitic 
limestone, and, like that of the Silkstone Series, was presumably 
deposited in a time of little rainfall, when the waters of the basin were 
sufficiently charged with lime to precipitate calcium carbonate. It is 
undoubtedly the product of the earliest (? Middle Miocene) occasion 
upon which Tertiary limestones of non-marine origin were formed in 
Queensland (v. Whitehouse, 1940). Although this limestone may have 
quite a large areal extent in the Petrie Series, it outcrops nowhere in 
the series, and is never likely to be of economic importance. 
A tentative Miocene age for the Petrie Series is also supported 
somewhat by the presence of diatomaceous earth in the series (v. Jones, 
1927), as a study of the literature on the subject has revealed the fact 
that diatoms were most prolific in Miocene times. It might be mentioned 
that diatomaceous earth has not been found in the Redbank Plains Series. 
Moreover, from the state of consolidation of the sediments, an age 
much later than Miocene for the Petrie Series seems to be unlikely. 
Finally, it seems certain that the clays, in which the series is par- 
ticularly rich, and not the oil shales, will eventually prove to be of 
greatest economic importance in the Petrie Series. 
This work has been carried out by the writer in part while an honours 
student within the Department of Geology, University of Queensland, 
and in part during the tenure of a research fellowship within the 
University of Queensland, financed by Commonwealth funds through the 
Council for Scientific and Industrial Research. He would like to thank 
Mr. 0. A. Jones and Dr!. W. H. Bryan for their helpful advice, and 
Professor IT. C. Richards for his personal interest in enabling him to 
carry out this work. He is also indebted to Mr. N. J. de Jersey for the 
determinations of the several fossil woods, and to Messrs. C. T. White and 
S. T. Blake for examining the small collection of Tertiary fossil plants. 
VII.— REFERENCES. 
Abbott, R. C. (1943). Personal Communication. 
Ball, L. C. (1932a). “ Shale Oil near Strathpine. ” Queensl. Gov. Min. J. xxxiii., 
221 - 222 . • 
Ball, L. C. (1932b). “ Bentonite, near Brisbane. ” Queensl. Gov. Min. J. xxxiii., 
384. 
Blake, S. T. (1942). Personal Communication. 
Bryan, W. H. (1925). “Earth Movements in Queensland.” Proc. Roy. Soc. 
Queensl. xxxvii., p. 38. 
Bryan, W. H. (1927a). In Abstracts of Proceedings. Proc. Roy. Soc. Queensl. 
xxxix., p. vii. 
Bryan, W. H. (1927b). In Abstracts of Proceedings. Proc. Roy. Soc. Queensl. 
xxxix., |p. xi. 
Chapman, F. (1932). In Ball, L. C., 1932. Queensl. Gov. Min. J. xxxiii., 384. 
Chapman, F. (1935). “Report of Samples of Surface Tertiary Rocks and a Bore 
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Cri£, L. (1889). “Beitriige zur Kcnntniss der Fossilen Flora einiger Inseln des 
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