September, 1939 
The Queensland Naturalist 
series, the Petrie Series, is a Tertiary deposit of compara- 
tively small extent, but which covers a large part of the 
area under consideration. The distinction between these 
formations is important, primarily from a topographical 
viewpoint. The area is almost entirely below the 200ft. 
contour line, the highest ground is in the north and north- 
west and becomes gradually lower to the east and south- 
east, where it falls almost to sea level. The Schists are 
confined to the higher north and north-west and are much 
folded, giving a series of frequently rather steep and nar- 
row ridges with usually narrow valleys between. The sides 
of the ridges are washed out by numerous waterways, so 
that this part of the area presents a very broken, though 
by no means rugged, topography. The result of this is 
that there is a large surface run-off, and except in the 
lower parts of the valleys the soil is shallow. In the Bunya 
Phyllites part of the area, except in the valleys, the ground 
surface usually consists of a layer of white quartz pebbles 
of various sizes. 
The Petrie Series on the other hand is characterised 
by gently sloping or undulating country with little surface 
run-off, deeper, generally sandy soil, which in depressions 
is frequently waterlogged during the wetter parts of the 
year. Local variations of soil-type however, are common. 
The Petrie Series is anything but homogeneous petrologic- 
ally, varying from pale-coloured fine-grained sandstone to 
conglomerates. These conglomerates are frequently ferru- 
gineous, and the pebbles derived from them often cover the 
surface of the ground. The ferrugineous types are chiefly 
developed in the south-west. Small patches of red loams 
occur sporadically in the east. One very important feature 
of the area is the presence of the North Pine River and its 
two tributaries, Sidling Creek and One Mile Creek. The 
presence of these streams is responsible for profound local 
variations in the soil and the accompanying flora. The 
river is bordered by alluvial flats, sometimes rather wide, 
sometimes almost obliterated by the proximity of the 
bordering < ‘flood-banks. ’ ’ Many of these flats are more or 
less covered with gravel, often very coarse (“Gravel 
Pits”). This gravel is deposited by the periodic floods to 
which the river is subject. An especially severe flood, 
such as occurred in February, 1931, may alter the position 
of these beds, sometimes scouring the pits almost complete- 
ly and depositing the gravel elsewhere. During the above- 
mentioned flood many farms were completely ruined by 
such a deposition of gravel. In the lower part of its course 
