11 
1918.] The N.Z. Journal of Science and Technology. 
must break away in blocks. In this manner the edge of the fall retains its 
clear-cut form as it retreats up-stream. 
Basaltic lava-flows are commonly columnar within but massive at the 
upper surface ; and, as many of the valleys of North Auckland have been 
Fig. 3.— The gorge below the falls. 
blocked by lava-flows, it is reasonable to expect that there should be many 
other falls similar to those of the Wairua. Examples of such are the 
Whangarei Falls and the Waitangi Falls at the Bay of Islands. 
Notes on the Geology and Mineral Occurrences of the 
Wakamarina Valley. 
By J. Henderson, D.Sc., Mining Geologist, Geological Survey 
Department. 
(A locality map and plans illustrating this paper appear in the Eleventh Annual Report 
of the New Zealand Geological Survey, 1917.) 
Topography. 
The Wakamarina River, one of the chief tributaries of the Pelorus, flows 
in a north-easterly direction through a deep, narrow valley and joins the 
main river at Canvastown, six miles from Havelock. The last-mentioned 
township lies near the head of Pelorus Sound, a feature produced by the 
drowning of the lower valley of the ancient Pelorus River. Probably at 
one time the sea extended beyond Canvastown, and the small flats in the 
lower valleys of the Pelorus and Wakamarina Rivers are gravel-filled arms 
of the Sound. Near Deep Creek, which enters the Wakamarina five miles 
from Canvastown, miners in search of alluvial gold have sunk through 
80 ft. of gravel in the stream-bed before reaching solid rock. In addition] 
