Arkell.1956.Jurassic..

KIMERIDGIAN-OXFORDIAN ?
NEW CALEDONIA 45 1
Sublittoral sandstones and green greywackes at Puen Island and Saint
Vincent Bay, with abundant fossil wood, and containing abundant belemnites
compared to Belemnopsis aucklandica (Hochst.). These beds also
yielded Holcophylloceras aff. polyolcum (Ben.) and a Lytoceratid (Avias,
i954> PP- 161-8).
Black shales near the centre of the island, on the upper Noumin and
upper Poya Rivers, yield forms of Inoceramus comparable with species
figured from the Oxfordian of Indonesia (Routhier, 1953, pp. 55-8;
Avias, 1954, pp. 168-70). A very poorly preserved Perisphinctid figured
by Routhier (1953, p. 57, pi. iii, fig. 1) from a limestone fossil-bed in the
shales was misidentified as Perisphinctes (Arisphinctes) schilli Oppel sp.
(holotype refigured Schneid, 1944, Palaeontographica, vol. xcvi A, p. 27),
which is an involute, Discosphinctes-Wke offshoot of Arisphinctes. Though
too poorly preserved for determination, the New Caledonian ammonite
(kindly sent me on loan) appears most likely to be a Kimeridgian Idoceras.
PLIENSBACHIAN ?
Beds with abundant Pseudaucella marshalli (Trechmann) as in New
Zealand, where they are pre-Toarcian and post-Hettangian and believed
to be Pliensbachian.
SINEMURIAN
The presence of Lower Sinemurian is indicated by an Arnioceras
found on Ducos Islet (Avias, 1954, p. 153, pi. xx, fig. 12).
HETTANGIAN
At Inaccessible Bay, close to Ducos Islet, have been found a number of
Psiloceratidae and Schlotheimiidae, including the genera Discamphiceras,
Laqueoceras, Waehneroceras (including 'Storthoceras' and 'Megastomoceras'),
Saxoceras and Schlotheimia; also a Paradasyceras. With the
Schlotheimiids occurs the pelecypod Otapiria marshalli (Trechmann),
described from the Hokonui Hills in New Zealand. This fauna has been
monographed by Avias (1954).
NEW ZEALAND
Although much still remains to be done in New Zealand geology, the
picture already built up is incomparably fuller and clearer than we can
yet obtain of any other part of the Papuan geosyncline.
Of the geosynclinal nature of the Jurassic sediments there can be no
doubt. The predominant rock-types are greywackes and mudstones,
with subordinate sandstones and conglomerates at several levels. The
total thickness near Kawhia Harbour, south of Auckland, on the North
Island, is about 4500 m. In the South Island the thickness diminishes,
being about 2200 m. at the south end. These measurements are hardly
comparable, however, owing to uncertainty about the upper boundary.
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