246 Dr. C. A. Cotton—Later Geological 
A Perrrop or Erosion AND DeEposttion FOLLOWING THE Mxsozorc 
Orogenic Movements. 
Upon the eroded surface of the oldermass lies a series of covering 
strata, and there can be no doubt that the mountain ranges which 
resulted from the Mesozoic orogenic movements had been subjected 
to erosion throughout a long period and reduced to at least moderate 
relief before the deposition of the oldest (Cretaceous) beds of this 
cover. It remains uncertain, however, whether at this stage complete 
peneplanation had been effected over any considerable area. In 
North Canterbury, indeed, Speight! has noted changes of facies in 
the limestone horizon of the covering strata, and there is certainly 
overlap in the lower beds, indicating that the eroded surface of the 
oldermass was there still somewhat hilly when submergence began, 
and that some hills survived as islands during a portion of the period 
of deposition of the cover. The available evidence points, however, 
to practically complete submergence of a large part of the north- 
eastern district of the South Island in the period of deposition of the 
Amuri Limestone (perhaps Eocene), and in some parts much earlier. 
The open-water origin and wide original extension of the Amuri 
Limestone have been demonstrated by McKay * and Hector.* Hector’s 
brief statement may be quoted: ‘‘ All these formations enter into 
great flexures that have been eroded to form lofty mountains, and 
the evidence is complete that they at one time spread continuously 
over a wide area. ‘This view is therefore completely opposed to the 
suggestion that has been made that the upper calcareous members of 
the Waipara formation were deposited among islands and in land- 
locked inlets after the erosion of the present valley systems.” * 
In the Marlborough area there was a long period of uninterrupted 
deposition extending far into the Tertiary, though to what stage of 
the Tertiary is not yet satisfactorily established. At this juncture 
great but quite local uplift occurred in certain areas, probably by 
block faulting, leading to the deposition in the neighbouring un- 
disturbed areas of that remarkable formation the Great Marlborough 
Conglomerate.°® 
During the early part of the long period of deposition in Southern 
Marlborough the neighbouring Marlborough Sounds district to the 
north and the South-Western Wellington district to the north-east 
appear to have escaped submergence, for the basal portions of the 
few small remnants of covering strata, namely, a small area at 
-1 R. Speight, ‘‘ The Intermontane Basins of Canterbury’’: Trans. N.Z. 
Inst., vol. xlvii, p. 350, 1915. ° 
2 A. McKay, ‘‘ On the Geology of the East Part of Marlborough,’’ Col. Mus. 
and Geol. Surv. N.Z., Rep. Geol. Expl., 1885, pp. 27-136, 1886; ‘*On the 
Geology of Marlborough and the Amuri District of Nelson,’’ ibid., 1888-9, 
pp. 85-185, 1890; ‘‘ On the Geology of Marlborough and South-East Nelson,”’ 
pt. ii, ibid., 1890-1, pp. 1-28, 1892 (see pp. 5-7). 
3 J. Hector, Col. Mus. and Geol. Surv. N.Z., Progress Report for 1885, 
1886 ; Progress Report for 1888-9, 1890. 
4 Progress Report for 1885, p. xviii. 
5 GC. A. Cotton, ‘‘ On the Relations of the Great Marlborough Conglomerate 
... 7: Journ. Geol., vol. xxii, pp. 346-63, 1914. 
