1920.] Morgan. — The Tertiary Beds of Central Otago. 
29 
THE TERTIARY BEDS OF CENTRAL OTAGO. 
By P. G. Morgan.* 
In the New Zealand Journal of Science and Technology , March, 1919, 
Dr. C. A. Cotton has an article entitled “ Problems presented by the 
Notocene Beds of Central Otago.” In 1914 I reported on deposits of the 
type discussed by Dr. Cotton at Waikaka and Waikaia, and recently I 
have carefully examined similar beds in the neighbourhood of St. Bathan’s, 
where sluicing operations have exposed magnificent sections of the “ older 
quartz drifts.” At St. Bathan’s the Tertiary or Notocene beds, named in 
upward order, consist of quartzose conglomerate and grit, lignite, car¬ 
bonaceous and light-coloured clays, and a thick fossiliferous clay stratum 
of a greenish colour, the whole series having a maximum thickness of nearly 
1,000 ft. To these beds I propose to give the name St. Bathan’s Series. 
Park’s name of Manuherikia Series would be applicable, but he included 
in that series* the ancient greywacke or “ sandstone ” gravels, known to 
the gold-miners as Maori Bottom (1906, p. 17 ; 1910, pp. 231, 359). These 
gravels are unconformable to the St. Bathan’s Series, but according to 
Dr. Cotton’s criterion must be included in the Notocene. They are certainly 
of fluviatile origin, whereas the most characteristic beds of the St. Bathan’s 
Series are, as McKay in my opinion has correctly stated, mainly of 
lacustrine and littoral origin. 
In discussing the age of the Notocene deposits Dr. Cotton suggests that 
in a portion of the Maniototo depression they are of Oamaruian age, but 
that “ it is quite possible that the Ngaparan terrestrial stage of the Oamaru 
district is overlapped inland by terrestrial facies of the higher stages of the 
Oamaruian and even of the Wanganuian.” The reason given for this 
tentative conclusion is that marine strata and interbedded basalt-flows are 
not found in the far-inland districts. Marine faunas of Middle or Older 
Tertiary age, however, occur south and west, as well as east, of north 
Central Otago. McKay writes, “ There is thus a central northern area of 
fresh-water deposits surrounded by a much larger area to the east, south, 
and west, which is undoubtedly, in the beds that immediately follow the 
quartz grit or drift, of marine origin ” (1897, p. 96). It is apparent that 
the transgression of the sea over Otago in Early and Middle Oamaruian 
times was tolerably widespread, and it is important to note that it reached 
the Lake Wakatipu district, thus lessening the probability of overlap 
being as great as Dr. Cotton suggests. The fact, if it is a fact,f that 
volcanic rocks are not found west of the eastern margin of the Maniototo 
depression, and therefore are not interbedded with the Notocene rocks, is, 
of course, purely negative evidence, of no weight where positive evidence 
is available. 
That there is overlap of the Notocene beds in Central Otago is practic¬ 
ally certain from our general knowledge of Tertiary conditions in New 
* This paper was written early in May, 1919. 
f McKay (1884, p. 81) speaks of feeble volcanic activity in the upper Manuherikia 
Valley. 
