NOTES ON THE PETRIE SERIES, SOUTH-EASTERN QUEENSLAND. 89 
shale can be traced along the strike in a north-westerly direction for 
several chains. Further exposures may also be found to the N.W. before 
the Brisbane Schist is finally reached, some one and a-half miles on in 
that direction. 
No outcrops in the Petrie Series could be located in a south-easterly 
direction from the fault on the Redcliffe road. 
From these observations, however, it seems that what is apparently 
the one reversed fault persists for a distance of at least six miles across 
the south-western portion of the Petrie Series. 
Furthermore, with reference to faulting, it is of interest to note that 
L. C. Ball (1932, p. 222) has suggested that the Brisbane Schists along 
the south-western margin of the Petrie Series may mark a faulted contact 
with the Tertiaries, the latter being either downfaulted on the N.E. or 
the former being overthrusted from the S.W. As he has stated, the 
alignment of the schist front here over a distance of 10 miles is strong 
presumptive evidence for this view. If this is so, it will be seen that 
it is roughly parallel with the fault which strikes N.N.W. to N.W. across 
the south-western portion of the Petrie Series and which has been 
described above. 
Some three-quarters of a mile to the south of the Redcliffe road 
outcrop we have evidence of lateral compression followed by tension. 
In, a quarry on portion 22, parish of Kedron, several chains to the S. of 
Graham road, can be seen a strong anticlinal fold at the crest of which 
a block has been let down to give a very spectacular trough fault. The 
excellent ripple marking of the sandstones in this small quarry also 
adds to its geological interest. Moreover, the folding and faulting seen 
in this quarry is probably genetically connected with the occurrence of 
a mud spring or “volcano” several chains to the E.N.E., in a depres- 
sion in the south-eastern corner of portion 152, parish of Nundah. This 
small mud volcano, from which cold mud may be seen slowly pouring 
forth usually some time after the cessation of rainfall in the area — pre- 
sumably the result of hydrostatic and not gaseous pressure — has 
attracted quite considerable interest since its appearance several years 
ago. It is pertinent to mention here that the Petrie Series is known to 
be water-bearing in many places, and that the subsoil generally is of a 
clayey nature. 
With reference to the age of these earth movements it can be said 
that, as palaeontological evidence suggests a probable Miocene age for 
the Petrie Series (see below), it seems that they are not of pre- 
Miocene age. It may be recalled that Jones (1927, p. 41) has stated 
that “The series is overlain at Bald Hills by upper division basalts.” 
As the upper basalts are considered to be of Pliocene age it appears 
likely that the folding and faulting have resulted from uplift and 
associated orogeny probably in Middle to Upper Miocene times. This 
was later followed by the extrusion of the basalt upon the tilted Petrie 
Series shales as seen in the road and railway cuttings at Bald Hills. 
Mention should also be made of the very slickensided decomposed 
basalt exposed in a quarry on the corner of Barfoot street and Bald 
Hills road, approximately two miles E.N.E. of Bald Hills, and very 
close to the eastern boundary of the Petrie Series as shown on Jones’ 
map. The intense weathering which has here preceded the slickensiding 
is rather puzzling, and hard to explain. However, as there seems little 
doubt that the basalt is of similar age to that which caps Bald Hills, the 
