1920.] Morgan.—The Tertiary Beds of Central Otago. 
31 
After discussing the conditions under which the Notocene beds of 
Central Otago accumulated, Dr. Cotton, in opposition to most former 
observers, comes to the conclusion that they are probably in great part 
of fluviatile origin. The upper greywacke gravels of the Manujierikia 
Series, though stated by Park to be lacustrine, are almost certainly fluvia¬ 
tile. As previously stated, they presumably form part of the Maori Bottom 
gravels, which are undoubtedly fluviatile. The green fossiliferous clay of 
the St. Bathan’s Series, with fresh-water “ mussels,” fish-remains, &c., 
is as certainly lacustrine. The lignite beds with their accompanying dark 
(carbonaceous) and light-coloured clays may perhaps be set down as pond 
or marsh deposits, or the question of their origin may be relegated to the 
general problem of the origin of coal. There remain for consideration 
the quartz conglomerates and grits which form the lowest beds of the 
St. Bathan’s Series. Dr. Cotton remarks that the question raised must 
remain open until the beds have been carefully re-examined with the hypo¬ 
thesis of fluviatile origin in mind. Further, he states that the lacustrine 
origin ascribed to the whole of the non-marine covering strata in Otago 
has not heretofore been questioned. These statements fail to do justice to 
McKay, who long ago pointed out that portions of the covering strata are 
of fluviatile origin, and came to the conclusion that the quartz drifts are 
lacustrine only after careful consideration of the fluviatile hypothesis, which 
he seems at one time to have entertained. In his report with the title 
“ On the Origin of the Old Lake-basins of Central Otago,” he writes, “ At 
this time a great river came from the west, having a course in an easterly 
direction, and to this we owe the auriferous drifts which are met with from 
the Bannockburn to the Upper Shag Valley ” (1884, p. 80). A few years 
later McKay’s views had changed somewhat. He mentions that, the Blue 
Spur gravels near Lawrence are fluviatile (1897, p. 92), whilst supposed 
younger quartz drifts at Criffel Face, Tinkers, and Devonshire Face 
appear to be the product of river-action (p. 114), but the auriferous 
parts of the older quartz drifts are not arranged like leads along an old 
river-bed, nor in fan-shaped deltaic deposits (p. 118). Such deposits, 
he thinks, have largely resulted from the pounding of material (fluviatile 
conglomerates, &c.) by wave-action, either on the sea-beach or on the 
shores of extensive inland lakes (p. 95). McKay specifically states that 
he considered the possibility of river-action producing a pure quartz 
gravel, and after carefully observing the gravels of the Molyneux, &c., 
came to the conclusion that seemingly no river in New Zealand at the 
present time does or can produce pure quartz gravel by current-action 
along its bed (p. 95). 
Some years ago, when at Waikaka, I gave careful attention to the 
question now raised again by Dr. Cotton, and formed the opinion that the 
quartz drifts in that locality were in the main formed with the aid of wave- 
action on beaches. The following passage may be quoted : “ It is of some 
importance to determine whether the quartzose gravels are river or beach 
deposits, and in the latter case whether they are marine or lacustrine. If 
they are of fluviatile origin, then they would mark the course of some 
ancient river and occur along a continuous but serpentine line. Beach 
deposits, on the other hand, would indicate the shore of the sea or of some 
ancient lake, and would lie not on a serpentine or meandering but on a 
straight or gently curving line or belt. Other differences will suggest 
themselves, but it is on the present occasion necessary merely to refer the 
reader to McKay, who has shown that the quartz drifts represent beach 
