Page 2 – Oldest fossils – Paleozoic
The Paleozoic era occurred 542–251 million years ago, and marks the spread of life on earth. It takes in the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian periods.
Cambrian (542–490 million years ago)
During the Cambrian period there was no life on land but there were plenty of creatures, such as trilobites, in the oceans. Cambrian fossils are only known from the Cobb valley and Springs Junction (west Nelson). These, the oldest-known New Zealand fossils (508 million years ago [Ma]), include sponges, brachiopods, molluscs, conodonts and trilobites within limestone.
The youngest finds the oldest
In 1948 Malcolm Simpson, a 14-year-old schoolboy at Nelson College, joined an excursion to the Cobb valley. On Wednesday 14 January, he hammered off some fresh limestone containing indistinct fossils and passed it to Professor Noel Benson, who considered it ‘indistinguishable molluscan remains’. Benson kept the sample and later found that they were Cambrian fossils, which made the rocks the oldest yet found in New Zealand. In 1998, on the 50th anniversary of the find, Malcolm was awarded the Wellman Prize by the Geological Society of New Zealand for his contribution to paleontology.
Ordovician (490–443 million years ago)
During the Ordovician period, earth’s first fish appeared. New Zealand Ordovician fossils include sponges, corals, brachiopods, trilobites, crustaceans, conodonts, and abundant graptolites. No terrestrial fossils are known. New Zealand’s Ordovician record is particularly good – the succession of graptolites is one of the most complete worldwide.
Ordovician strata are found in north-west Nelson at the Aorangi mine, Mt Patriarch, and in the Cobb, Tākaka and Wangapeka valleys. Other localities are the Baton River, Cape Providence and Preservation Inlet.
Silurian (443–417 million years ago)
It was during the Silurian period that animal life first appeared on land. It also marked a major expansion of many marine invertebrate groups that had first appeared in the Cambrian and Ordovician periods.
Silurian fossils are rare. They have been found in the Pikikiruna Range and Wangapeka valley in north-west Nelson. Fossils include six species of brachiopod. Small amounts of coral, crinoid and bivalve fossils are also found.
Devonian (417–359 million years ago)
Often called the age of fishes, the Devonian period is marked by the rapid establishment of all types of marine and freshwater fish. Fossils, which include many early marine life forms, are found near Reefton, Baton River and Lake Haupiri. There is no New Zealand record of Devonian land-based plants and animals.
Carboniferous (359–299 million years ago)
In the Carboniferous period there were lush forests and warm temperatures around the world. It is called Carboniferous because a lot of coal (which is mainly carbon) was laid down at this time.
However, there is no New Zealand record of Carboniferous terrestrial plants and animals. Carboniferous fossils are extremely rare and are only known from north Otago (near Dunback) and South Canterbury (near Kākahu). The only fossils present at both localities are conodonts and fish-scale fragments.
Permian (299–251 million years ago)
The oldest-known North Island fossils are early Permian (about 270 Ma). They occur in Northland (Whangaroa Harbour, Bay of Islands) and near Wellington (Red Rocks and the Hutt Valley). The fossils are diverse but they are all marine. The most common are fossil plankton and in particular radiolarians.
Among the shelly fossils, brachiopods were especially diverse and abundant, molluscs less so. Distinctive mussel-like shells (atomodesmatinids) were so numerous in places that they have formed vast sheets of limestone. Rare vertebrate fossils have been collected (conodonts, fish scales and marine reptiles).
New Zealand’s oldest-known fossil pollen, spores and terrestrial plant fossils (265 Ma) are from Southland. In the Wairaki Hills, 10 specimens of Glossopteris leaf have been found in marine sedimentary rocks. No actual terrestrial rocks are known – these leaves washed down from Gondwana onto an ancient sea floor, which eventually turned into the sandstone of the Wairaki Hills.
The end of the Permian period marks earth’s largest ever extinction – two-thirds of plant and animal life died out. It may have been the result of a sudden climate change.