Arkell.1956.Jurassic..

NEW ZEALAND 453
faulting and volcanicity. These movements raised the present mountains
and determined the existence and approximate shape of the country.
In the North Island tectonic events were more complex and there are
Aptian greywackes with considerable volcanic material.
Despite its great thickness, there is no reason to suppose that the
Jurassic system in New Zealand is complete. Numerous changes of
lithology, from greywackes and claystones to coarse conglomerates, and
even 'fossil forests', indicate repeated movements in the trough and its
surroundings. The faunas, though including Hettangian and Tithonian,
are far from complete. As yet no ammonites definitely assignable to the
Sinemurian, Bajocian, Bathonian or Oxfordian have been found. Disconformities
certainly and unconformities possibly occur, but their
detection will be difficult owing to complexity of structure, rarity of fossilhorizons,
and discontinuity of exposures. No red beds or salt deposits
occur in the Jurassic or any other system in New Zealand; which suggests
that the country has never formed part of a major continental landmass
(Fleming, 1949, p. 74).
As the most southerly and most remote in the old world, the Jurassic
rocks of New Zealand are of great palaeontological interest. Despite their
remoteness they have less endemic fossils than most isolated areas. The
ammonites, whether Hettangian, Toarcian, or Tithonian, nearly all
belong to ordinary cosmopolitan genera, with special affinity with species
found in Indonesia and New Guinea, but also Mexico and Japan. Some
pelecypods are astonishingly European. For instance, there occur Oxytoma
cf. cygnipes (Young & Bird), Meleagrinella cf. echinata (William Smith)
and Camptonectes cf. lens (Sowerby), all first described from the Lias and
Oolites of England. In the Lower Jurassic, as in the Trias, the common
pelecypods tend to be endemic. There is a striking abundance of Pteriidae,
Myalinidae and Buchiidae. The Upper Jurassic pelecypods are largely
identical with those of the Spiti Shales and are dominated by the genus
Buchia (= Aucella) (at one time believed to be boreal), which ranges from
Oxfordian to Tithonian and higher (Marwick, 1926, 1934, 1935). One
notable endemic Buchiid genus, Pseudaucella, is a rock-former on a large
scale in New Zealand as in New Caledonia.
The Jurassic rocks of the two islands are grouped as follows, with their
approximate thicknesses (Willett, 1948, p. 14; Marwick, 1950, 1953, and
subsequent information):—
KAWHIA, NORTH ISLAND SOUTH ISLAND
Upper Jurassic
JHSESS. } • >40om.(+ ?) Metaura series . . xo 5o m.
j Middle Jurassic
\ Temaikan series 600 m.? \
Lower Jurassic J- Putataka and Flag Hill
series . . . 500 m.
f Ururoan series \ J
\ Aratauran series / ' ^ " Bastion series . . 660 m.
Total 4500 m. Total . 2210 m.
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