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BEnson.—Structural Features of the Margin of Australasia. 131 
north-westwards into Sumatra. 1% is, as yet, quite impossible to indicate 
the direction of superficial thrust of these crust-movements in New Zealand. 
The dips of the Tertiary rocks are generally moderate (30°-40°), and the 
strike is so variable in orientation that it is difficult to pronounce any 
direction as being that of the prevalent strike. Crust-movement appears 
to have continued intermittently throughout the Gisborne district (Hen- 
derson and Ongley, 1920) during the Cretaceous and Tertiary period, and 
recently Ongley and Macpherson, during their official geological survey of 
the East Cape district, have found that the Cretaceous rocks are very 
strongly folded with a north-west-south-east strike, and are invaded by a 
pre-Miocene dioritic complex, the source, perhaps, of the dioritic pebbles 
in the basal conglomerates of the Miocene beds of the iy sborne district. 
is Hawke’s Bay McKay (1877) suada the occurrence of strongly 
folded Cretaceous rocks gare th the gently undulating Pliocene beds, 
and this has been confirmed by Dr. Thomson, who (in a private com- 
munication) has compared the Cretaceous rocks lithologically with those of 
the Middle Cretaceous (Clarentian series) of the South Island. With them 
he would include the “ East Coast series” formerly referred tentatively 
to the Lower Cretaceous by Morgan (1915) and the writer (1921), and 
considered to be the latest of that great series of Mesozoic sediments 
laid down before the Cretaceous orogeny, though the relationship of this 
series to the characteristic, highly dislocated, and definitely pre-Cretaceous 
greywackes and argillites has not yet been critically examined. Again, 
in Palliser Bay, east of Wellington, McKay (1879) recorded the presence 
rmably beneath Tertiary marine beds, and Thomson observed pebbles 
of Cretaceous rocks in the Upper Tertiary sediments in the same region. 
In the South Island there is as yet no clear evidence of an early Tertiary 
vel on Bou on in and block-movements during the period seem 
used smal ar unconformities, disconformities, and over- 
laps in ` different ет ы not apparently confined to any опе period, 
T d 
RE i (1921) and the writer (Benson, 1921). A few examples of extremely 
localized overfolding of Tertiary rocks, as at Nelson and on Lake Wakatipu, 
may be local thrustings connected with the Plio-Pleistocene block-movements. 
In Pleistocene times this тикове and block-faulting with tilting 
were extremely important, and were the chief processes by which the 
present topography was анда. The nature of these movements 
has been elucidated by Professor Cotton in a succession of important 
papers (e.g., 1916, 1917, &c.). The chief system of longitudinal fractures 
and warpings is of those which run north-north-east to north- east, cutting 
obliquely across the strike of the a folds. They have in many 
regions blocked out the main features of the coast-lines, subsequently 
modified by the normal processes of marine erosion, so that the strike- 
ridges meet the coast en echelon. · In the south, however, where the trend- 
line of the Otago schists bends to the south-east, the coast truncates the 
in the origin of which is thus bound up with the structural development 
of New Zealand. Besides this main longitudinal direction of fracturing 
there are minor diagonal or transverse fractures and warpings in certain 
regions. 
5* 
