A Great Southern Continent

THE earliest European navigators who visited New Zealand came here in search of a Great Southerern Continent. Tasman thought he had discovered it; Cook disproved its existence. But millions of years earlier, during a great part of the zoic Era, New Zealand did actually form the shore-line of a great continent, named Gondwana-which extended far to the west. The Tasman lid not then exist and New Zealand was joined to Tasmania and Australia.

During this time spoil from the eastern part of Gondwanaland was washed down and deposited on the present site of New Zealand. But, owing to fluctuations of the continental margin, sometimes it lay beneath the sea, sometimes it formed lying coastal land with widespread lakes or lagoons. As a result, there were built up coarse marine sandstones and pebble-beds of great thick­ness which alternated with fresh-water plant-bearing strata.

The marine fossils of  the Mesozoic Era reached New Zealand by the ancient sea-way which stretched northwards to New Caledonia, thence via the Malay Archipelago to the Himalayas (still unborn) and so to the Mediterranean. The characteristic fossils of this era are the spirally coiled ammonites, relatives of the octopus. With them are found extensive banks of mussel-like shells and representatives of some Paleozoic types, Marine Mesozoic rocks are best developed in the Ranges of Southland, but they are also found, often without fossils, in other mountainous parts of both islands.

The Mesozoic Era is known not only by fossil animals, but by fossil plants. At intervals during Upper Triassic and Jurassic Periods the New Zealand area was above sea-level long enough for forest to flourish. The oldest are found in Canterbury – at Mount Potts in the Rangitata Valley in the Clent Hills. Slightly younger are those in the Malvern Hills, at Mokoia, near Gore, and, most famous of all, at Curio Bay, near Waikawa, Southland. The Curio Bay beds, indeed, are a remarkable example of a petrified forest dating back to Jurassic times. Here the plant-beds are exposed to sea erosion, and the shore-line is thickly strewn fallen trunks and limbs of petrified trees, many of them over fifty feet in length and two feet across. Even well-preserved impressions of leaves may be found in abundance. Flowering plants had not yet made their appearance and these fossils are remains of fern-like plants, (a kind of palm), and conifers.