1919.] 
Cotton.—Notocene Beds of Central Otago. 
69 
PROBLEMS PRESENTED BY THE NOTOCENE BEDS 
OF CENTRAL OTAGO. 
By C. A. Cotton, D.Sc., F.G-.S., Victoria University College, Wellington. 
The beds in Central Otago which I have found it convenient to term 
“ covering strata ” (1916, 1917), on account of their unconformable junc¬ 
tion with a deformed undermass, on the planed surface of which they lie, 
have long been recognized as a formation that is largely non-marine. By 
Hutton and by Park the non-marine beds were thought to have accumu¬ 
lated as lacustrine deposits in isolated basins. McKay, however, though 
he accepted the lacustrine theory, maintained their former continuity, and 
regarded them as older than the depressions in which they are now found. 
I have recently pointed out the relation between the attitude of the cover¬ 
ing beds still preserved in the depressions and the slopes of the stripped 
or fossil plains forming the back slopes of the tilted-block mountains that 
separate the depressions. This seems to prove that the beds were laid 
down prior to the Kaikoura deformation, to which the relief forms of 
Central Otago are due, and definitely assigns them to the Notocene period 
as defined by Thomson (1917, p. 408). 
The object of the present note is to call attention to two of the problems 
presented by these beds, namely : (1) With what stage of the marine Noto¬ 
cene are they to be correlated ? and (2) Under what conditions did they 
accumulate ? 
The Question of Correlation .—According to an interpretation of the 
structure in north-eastern Otago favoured by Hutton and Park, a period 
of folding and erosion intervened between the periods of deposition of the 
older Notocene (Cretaceous) and of the more widely distributed younger 
Notocene strata in this locality. Should this view be proved correct it 
may follow that the period of planation during which a level floor was 
prepared for the younger Notocene cover in Otago was within the Noto¬ 
cene (post-Cretaceous, approximately). Angular unconformity between the 
younger and older Notocene beds at Shag Point cannot, however, be 
regarded as demonstrated, and the structural relations of the latter to 
the great plain of erosion which truncates the schists and greywackes 
are unknown. The great denudation that followed the post-Hokonui 
deformation was unquestionably far advanced in earliest Oamaruian time, 
whether or not it was interrupted by movement within the Notocene. It 
was pre-Oamaruian, for the planed surface passes, in eastern Otago, directly 
under the Ngaparan or Lower Oamaruian. 
Inland, the marine fauna which, as McKay notes (1884), occurs in 
the Notocene beds of a portion of the Maniototo depression is probably 
Oamaruian, though little is definitely known about it as yet; while the 
development of a large area of basaltic lava sheets which but for their 
partial removal by erosion from uplifted areas would apparently be con¬ 
tinuous with the basalts in the Ototaran of the Oamaru district affords 
another means of tentative correlation. 
Farther inland both these criteria fail; and it is quite possible that the 
Ngaparan terrestrial stage of the Oamaru district is overlapped inland by 
