122 PROCEEDINGS OF THE ROYAL SOCIETY OF QUEENSLAND. 
Petrie Series are considered as being most probably Miocene in age, and 
the Baffle Creek Tertiaries and the Redbank Plains Series as probably 
Oligocene. This has confirmed Hills’ conclusion (1943), from a study of 
the fish fauna of two of these basins (Redbank Plains and The Narrows), 
that the Tertiary deposits of Eastern Queensland are not all 
contemporaneous. 
The environmental conditions of deposition for these ostracod- 
bearing shales indicate that the lakes were largely shallow but probably 
of a permanent nature, that their floors were covered in part with mud, 
decayed vegetable matter and algae, that the temperature of the water 
was probably very close to that found in similarly situated lakes today, 
and that the lakes were all freshwater ones. Slow subsidence during 
deposition, also, is indicated by the thicknesses of ostracod-bearing shales 
that contain a shallow-water fauna. 
The absence of ostracods from some of the oil shales and their 
presence in non-bituminous shales show that they are not the principal 
contributor to the kerogen of the oil shales in these basins. Their common 
occurrence in them, however, is natural, since they favoured an 
environment rich in algal material such as that in which these oil shales 
were formed and, in most cases, they were apparently buried in situ. By 
partial decomposition of the soft parts of the animal, however, the 
ostracods may have contributed in some small measure to the formation 
of the oil shales. A partial animal origin has, in fact, been suggested by 
Ball (1914b, p. 74) for some of The Narrows and Baffle Creek oil shales, 
and by the present writer (1944, p. 98) for some of the Petrie Series 
oil shale. 
It is probable that the ostracods contained in the shales of some of the 
Tertiary basins, other than The Narrows, will also prove of value for zonal 
correlation purposes in the future. Since drilling operations will be 
necessary for the adequate study of all these basins, more sets of bore- 
cores should eventually become available and so enable attempts at 
zonation and correlation of the strata to be made. 
In conclusion, it may be said that, although the ostracods have not 
yet proved of very great value for the determination of the precise age 
of the various deposits, they have already given some indication of their 
probable ages. When more work has been carried out on Tertiary and 
Recent freshwater ostracods, and the geological ranges of the various 
genera and species have been accurately determined, more precise age 
determinations for some of these basins may be possible. 
Acknowledgments. 
This work was financed by the Commonwealth Government 
Grant through the Council for Scientific and Industrial Research 
to the University of Queensland. The writer would like to thank 
Mr. 0. A. Jones and Dr. W. H. Bryan for their helpful advice, and 
Professor H. C. Richards for his personal interest in enabling him to 
carry out this work. The material from The Narrows was submitted 
for examination by the Chief Government Geologist, Mr. L. C. Ball. The 
drawings are the work of Mr. R. Gra dwell. 
