Arkell.1956.Jurassic..

CHAPTER 18
NEW GUINEA, NEW CALEDONIA, NEW ZEALAND
AND AUSTRALIA
NEW GUINEA, NEW CALEDONIA, NEW ZEALAND
It is not altogether imagination to link these three distant countries
geologically as relics of an orogenic belt, most of which has foundered
beneath the sea. The trend-lines of the great central range of New
Guinea, called in its south-eastern part the Owen Stanley Range, are
continued by the elongated island of New Caledonia, although separated
by 1200 miles of ocean; and after another gap of iooo miles the same trend
is picked up again at North Cape, New Zealand, and continued, after a
virgation in North Island with the Kermadec-Samoa ridge, through the
Southern Alps of the South Island. This reconstruction forms an arc
5000 miles long, which Suess called the '3N arc' (New Guinea, New
Caledonia, New Zealand). The south-easterly turn taken by the trendslines
at the south end of the South Island, New Zealand, suggests that
the orogen links up under the sea with the fold-ranges of West Antarctica
and the Andes, to complete the circum-Pacific orogenic ring.
Geological exploration of New Guinea and New Caledonia is still
in infancy, but enough is known to indicate essential parallelism in the
Jurassic system in all three countries. In fundamental contrast with
Australia, a continental area in the Jurassic, the '3N arc' was a regon of
geosynclinal marine deposition. New Zealand has about 4500 m. of
Jurassic, most of it greywackes and mudstones, interspersed with grits
and conglomerates, such as are more usually associated with the Lower
Palaeozoic systems in Europe. The Upper Jurassics of both New Zealand
and New Guinea show strong resemblances, lithologically and palaeontologically,
to the Spiti Shales of Indonesia and the Himalayas. In
both New Zealand and New Caledonia there are indications of a land area
to the west, which supplied the sediments to the trough. This land must
have lain on the site of the Tasman and Coral Seas. Geophysical and
geological lines of evidence converge to the conclusion that these seas
are a foundered land area, quite different from the Pacific Ocean.
It is therefore a hypothesis less shaky than many in geology, that the
'3N arc' coincides with a Jurassic sinking mobile belt, the Papuan Geosyncline,
which was folded and upraised in the manner of an active orogen
during the Cretaceous and Tertiary orogenies; furthermore, that this
orogen separated greater-Australia (inclusive of the Tasman and Coral
Seas) on the west from the Pacific Ocean on the east; and that between
the geosyncline and the ocean to the east there may have risen a chain or
445
http://jurassic.ru/