GEOLOGICAL NOTES ON THE PIONEER RIVER BASIN. 
73 
The S.E. fall, however, has a noteworthy effect. The Pioneer here 
receives many streams from the main scarp — the N. boundary — but not 
one from the South or East. 
The north branch of Sandy Creek, and Baker’s Creek draw water 
from within a stone’s throw of the very river bank and three sugar 
mills have happily utilised this peculiarity to dispose of their effluents 
without contaminating their water supply. The creeks themselves show 
the same peculiarity. Rocky Creek draws water from por. 104, Par. 
Greenmount, on the very brink of Baker’s Creek. 
GENERAL GEOLOGY. 
The sediments of the area under discussion belong to the Bowen 
Series, but igneous 'activity subsequent to their deposition has been so 
intense as to obscure all but small patches of this series, this igneous 
activity producing first an extensive series of diorites and later 
rhyolites, the two types covering the greater part of the area and 
obscuring the underlying rocks. In addition to these two main types, 
others with their hypabyssal equivalents occur in the area. 
As is well known, with a geological survey of this kind which 
involves igneous rocks an intensive survey of an area is required in 
order to produce a connected picture of the distribution of the various 
igneous types, but as this is in the nature of a reconnaissance survey 
it has been thought advisable to record localities of types rather than 
construct a pretty picture based on insufficient data, and it is to this 
end that the following types and their localities are discussed. 
Diorites. 
The diorites with, in places, andesitic tuffs form the largest and 
most marked part of the area. 
From Black Mountain, which dominates this igneous mass, outcrops 
of diorite radiate in every direction — to Seaview, Green Island, Habana, 
Eimeo, Black’s Beach, Slade Pt., Glenella, Mt. Oscar, Mt. Bassett, and 
as far as Brampton Islands. 
In addition to this large single area, diorite masses separate Goose- 
pond Creek from McCready’s Creek on the one hand and Fursden Creek 
on the other; Fursden Creek from the east branch of Nebia Creek 
and also the eastern and western branches of Nebia Creek. 
The interesting mass of Turner’s Sugarloaf (N.W. of por. 499, 
Par. Bassett), which is weathered felsitic material (probably a dyke), 
is surrounded by masses of diorite which occur on the hill to the S.E. f 
and four smaller spurs to the S.W. Two branches to the north are 
dioritic ; the more western of these drops considerably to form two yet 
smaller ridges at the head of Reliance Creek. 
