32 The N.Z. Journal of Science and Technology. [Feb. 
deposits from which soft rocks have been almost completely eliminated 
by wave-action. . , . It is not intended to maintain that the whole 
of the Miocene beds are of lacustrine origin. . . . The upper layers of 
quartzose gravel seen in the Waikaka Valley below the township appear 
to be of fluviatile rather than lacustrine origin” (1914, p. 150; 2nd edition, 
1915, same paging). 
My recent examination of the splendid exposures of the quartz drifts 
at St. Bathan’s and Muddy Creek (to the eastward) lead me to believe 
more firmly than ever that McKay was essentially correct in his ex¬ 
planation of the origin of the quartz conglomerates and grits. It 
may be repeated that he does not state that the quartz drifts are 
wholly lacustrine ; on the contrary, he gives full consideration to the 
hypothesis of fluviatile origin, and considers portions of the drifts to have 
that origin. 
Dr. Cotton says that it is obviously impossible to explain a widely 
extending bed of fine quartz gravel or greywacke gravel laid down with 
horizontal bedding as a lacustrine deposit.” The greywacke gravels being 
admitted by McKay and myself to be fluviatile, discussion is narrowed to 
the quartz gravels and the associated beds. These do not, as a rule, exhibit 
original horizontal bedding in those localities where I have seen them. 
Current bedding is common, and the lensoid character of many of the minor 
layers is easily traced. The carbonaceous clays and lignites were apparently 
all formed under water. Some of the clays certainly.were, for they contain 
Diploclon impressions. The purity of the quartz conglomerates, as McKay 
pointed out, indicates wave-action on beaches. If, however, Dr. Cotton 
refers to the attitude of the quartz-gravel beds as a whole, then reference 
may be made to J. E. Marr’s exposition of the manner in which a nearly 
horizontal sheet of conglomerate may be built on an advancing or receding 
shore-line (1898, p. 117). The widespread nature of the quartz drift is, 
moreover, evidence of overlap, as Marr shows. Barrell (1912, p. 390) has 
demonstrated that important deltaic deposits may lack typical foreset (and 
bottomset) beds. Dr. Cotton’s statement, then, as I understand it, may be 
successfully challenged. 
The quartz of the quartz drifts is not, as generally supposed, all derived 
from areas of schist. The older rocks near St. Bathan’s are greywackes 
and argillites, such as those that form the Hawkdun Range. In places 
these rocks contain numerous irregular quartz veins— e.g., at Vinegar Hill, 
where quartz wash rests on their planed surface—and possibly a great 
part of the quartz gravel here and at St. Bathan’s comes from the grey¬ 
wacke series. 
Attention may be drawn to the fact that in the Westport district highly 
quartzose conglomerates and grits occur in Eocene coal-measures. In 
places, especially at Mount Rochfort, there is a great thickness of fine quartz 
conglomerate at or towards the base of the measures. This must be 
regarded as largely formed by wave-action on lake-beaches. The coarse 
grits and sandstones of higher horizons exhibit remarkable current bedding. 
I regard them as largely fluviatile, but deposition of portions in standing 
water is also clearly indicated. The ponds or lakes, however, in this case 
were small and short-lived. 
Owing to the auriferous character of the quartz drifts of Otago, the 
questions of their age and origin are of more than academic importance. 
It is much to be desired that the fossils they contain (lignitized and silicified 
