The flowers of Pakawau

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Liz Kennedy

Think of fossils and dinosaurs, trilobites and shells may spring to mind, but probably not flowers. Yet since 1992 more than 100 fossil flowers have been collected from 70-million­year-old rocks near Pakawau, on the western flank of Golden Bay. They are the first flowers of Cretaceous age to be reported from New Zealand, and no fossils quite like them are known anywhere else on earth.

Like many of New Zealand’s most important and spectacular fossils, they were discovered by a woman: Liz Kennedy, a paleobotanist with the Institute of Geo­logical and Nuclear Sciences, in Lower Hutt. She is in good company Think of Jean Gyles, who found a giant Jurassic ammonite, Joan Wiffen, who discovered New Zealand’s first dinosaur fossils, and Mary Ann Mansell, who found the very first fossil bone to be recognised as dinosaur (see New Zealand Geographic, No. 46).

The Pakawau flowers appear to be all the same type, as if produced by one kind of tree or shrub. The identity of that plant has yet to be determined.

The flowers are conspicu­ous, with long tapering perianth arms forming a star around a broad central disc, which bears the carpels containing the seeds. Delicate parts of the flowers (petals and stamens) have not been found, and the true nature of the perianth has yet to be determined. Researchers are hopeful that one day a fully intact specimen will be found.

The flowers are associ­ated with other plant fossils, including the leaves of flowering plants—dicots mainly (possibly members of the protea and laurel families), but also a few monocots, as well as conifers and ferns. Some seeds and/or fruits are also present.

The Pakawau fossils are preserved as impressions in greyish-white sandy quartz-rich siltstone, which prob­ably accumulated in a small lake or pond within a broad, bush-covered floodplain.

Some 70 million years ago, New Zealand was a sizeable continental land­mass with a subdued topography, not unlike that of Australia today, but well separated from Gondwana. It was slowly sinking beneath the sea—literally settling down after the harrowing thermal paroxysms that caused it to rift away from the mother continent about 85 million years ago.

The discovery of the Pakawau fossils has an unexpected connection to the New Zealand economy. The rocks they occur in, known as the Rakopi Formation, are widely considered to be the ultimate source of much of New Zealand’s oil and gas reserves, including the Kupe, Maui and recently proven Rimu fields.

Fossil plant beds and coals within the Rakopi rocks have been buried to great depths within the Taranaki sedimentary basin and literally cooked under the influence of sustained temperature and pressure over a long period of time, to produce oil and gas, which migrate, generally upwards, to become trapped at higher levels within suitable reservoir rocks. In the past 30 years, the discovery and extraction of these valuable resources have made us not only more economically self-sufficient, but more confident as a nation.

Little wonder, then, that there is an urgent need to conduct more research into these ancient sediments. Knowledge of the plants that forested New Zealand 70 million years ago may help us understand more about the characteristics of our oils and gases.

Perhaps the Pakawau flower could serve as a brand for New Zealand-based oil exploration companies operating in the Taranaki basin. Worth billions, the Rakopi Formation is a treasure to the New Zealand economy and our natural heritage.

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