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Fossils

by  Hamish Campbell

Fossils are glimpses into past life. They are a record, in the rocks, of long-gone plants or creatures, and environmental conditions. Next time you pick up a stone, have a closer look – perhaps it has a story to tell.


What are fossils?

Fossils are the preserved evidence of past life. They may include organic remains such as wood, shells, bones and teeth that have been buried, mineralised, and turned to stone. But the term fossil can also apply to anything dead and preserved. Fossils can be mummified, pickled, dried out or frozen. There are also trace fossils – records of animal behaviour such as burrowing, breathing, feeding, defecating, moving, resting, mating, nesting, growing, playing, exploring, fighting and hiding.

Most fossils are mineralised. To become a fossil a dead organism must be preserved, which requires eliminating the agents of decay and destruction – oxygen, bacteria, radiation and erosion. Fossil preservation varies greatly, and the optimum conditions for preservation rarely occur.

How fossils are preserved

When plants and animals die, they generally rot or are eaten. This happens quickly – in a matter of days or months. The hardest parts (wood, teeth and bone) are the last to decay. If they become buried in sediment such as gravel, sand, silt and especially mud, they are most likely to be fossilised. Fossilisation often involves shell, bone and wood being slowly replaced by minerals.

Measuring time

Sedimentary rocks and fossils are a history of past environmental conditions. Rock layers can be thought of as pages in a book and fossils as words. While the order of the pages is important, the words reveal the most.

Species are restricted to a certain geological time period; they evolve, live for a certain time and then become extinct. This makes fossils useful – finding a certain species, and knowing when it lived and died, enables geologists to date rocks.

Geologists use a chronology known as the geological timescale. It is divided into chunks of time called periods. The age scale of geological periods is measured in millions of years, and is denoted by the abbreviation Ma (Mega-annum in Latin). For example, 30 Ma means the rock formed 30 million years ago.

Geologists have relied on fossils to establish periods, and to tell them apart. A new period generally represents some abrupt change to life on earth. For example, the end of the Permian period is marked by a major extinction event. The following period, the Triassic, is characterised by very different fossils.

By international agreement, the major time periods have been subdivided into epochs. For example, the early Cenozoic period includes the Paleocene, Eocene and Oligocene epochs, and the Jurassic includes the early, middle and late Jurassic epochs. Epochs are further subdivided into stages, so the late Triassic epoch includes the Carnian, Norian and Rhaetian stages.

New Zealand has a very detailed local timescale with its own set of formal names. For example the late Miocene epoch includes the Tongaporutuan and Kapitean stages. These are named after places where rocks of this age are well exposed.

New Zealand’s fossils

New Zealand is rich in fossil-bearing sedimentary rocks. A huge diversity of past life is preserved, including trilobites, graptolites, brachiopods, belemnites (relatives of squid), ammonites, dinosaurs, marine reptiles, whales, turtles, crocodiles, fish, sharks, crabs, penguins and other aquatic birds. Many plants have lived on the ever-changing landmass of New Zealand, and these are seen as coal, fossil seeds, pollen, and up to full-size fossil tree parts. There are also large numbers of microfossils, which can only be seen clearly through a microscope.

While all geological periods from Cambrian (542–490 million years ago [Ma]) to Cenozoic (65–present day) are represented, New Zealand’s fossil record is not especially complete, and is poor for a few periods. For instance, very few Carboniferous (359–299 Ma) and Silurian (443–417 Ma) fossils have been found in New Zealand.

Curious beginnings

Joan Wiffen, the first fossil collector to extract dinosaur bones in New Zealand, explains the genesis of her interest:

‘As a child in the early 1930s, I roamed the bare brown hills of the Hawke’s Bay sheep country. There were shelly layers in the rough limestone outcrops, particularly where the weather and rubbing animal bodies wore ledges into the rockfaces along the tracks. I would run my fingers over the shells and wonder how they got there’. 1

The fossil record is dominated by the remains of marine life. The most readily visible fossils are late Cenozoic shells (less than 23.8 Ma). The most common fossils are of plankton – the skeletal remains of microscopic single-celled plants and animals.

There are also terrestrial or freshwater sedimentary rocks and fossils. The most widespread are coal deposits, which form from plant debris. These accumulated on land, mainly in lakes, rivers and swamps. Fossil pollen and spores are also abundant. Curiously, very few terrestrial animal fossils have been found, and the fossil record of modern birds (including moa and kiwi) and reptiles (tuatara, geckos, skinks) is surprisingly short – less than 2 million years.

Footnotes
  1. Joan Wiffen, Valley of the dragons: the story of New Zealand’s dinosaur woman. Auckland: Random Century, 1991, p. 11. › Back

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.


Age of the dinosaurs – Mesozoic

The Mesozoic is the age of dinosaurs. It occurred 251–65 million years ago, and includes the Triassic, Jurassic and Cretaceous periods. Most of the greywacke rocks dominant in the New Zealand mountains, including the Southern Alps and those in the central North Island, originally accumulated as sediment on the ancient Pacific Ocean floor during this time.

These rocks were uplifted and incorporated into the eastern margin of continental Gondwana. Then, about 85 million years ago the New Zealand continent, Zealandia, broke away, carrying with it a cargo of plants and animals, including dinosaurs.

Triassic (251–200 million years ago)

Worldwide, the Triassic period is noted for the emergence of marine molluscs and marine reptiles, while on land the earliest dinosaurs and mammals appeared. However, their fossils have not been found in New Zealand. The oldest terrestrial animal fossil is some 245 million years old. It is an amphibian like a large salamander (about 3 metres long), found in rocks near Mataura Island, Southland.

Fossil-bearing Triassic rocks are scattered around the country. Fossils include representatives of most marine invertebrate groups. Vertebrate fossils of conodonts, fish and marine reptiles are generally rare. Dinoflagellates (a type of marine plankton) first appear in younger Triassic rocks. Plant fossils (wood and leaves), fossil seeds, spores and pollen are also present.

Jurassic (200–145 million years ago)

During the Jurassic period, brachiopods (lamp shells) declined globally while molluscs such as ammonites and belemnites (relatives of squid) flourished. On land, dinosaurs and birds rose to prominence and flowering plants first appeared. Jurassic marine fossils include plankton, corals, many other marine invertebrates and rare sharks and bony fish.

Jurassic land fossils include well-preserved tree stumps (Curio Bay, Southland). Fossil wood, leaves, seeds, spores and pollen have been documented from numerous layers. The oldest New Zealand fossil insect (an ancestor of the wētā) is Jurassic. A single Jurassic dinosaur fossil has been found near the Waikato River mouth.

Cretaceous (145–65 million years ago)

The Cretaceous period is noted for the global rise of calcareous plankton (major contributors to chalk and limestone formation), marine reptiles (mosasaurs, elasmosaurs), and on land the spread of the flowering plants.

New Zealand’s oldest Cretaceous fossils are plankton. Younger Cretaceous marine fossils include plankton, invertebrates and vertebrates (fish and marine reptiles).

Terrestrial rocks include coal layers with wood, leaf, seed and pollen fossils. New Zealand’s oldest fossil flowers are of Cretaceous age – found near Pakawau, Golden Bay. Rare insect and vertebrate fossils are also known. A single fossil locality (inland Hawke’s Bay) has yielded dinosaur, turtle, pterosaur and perhaps bird fossils from sedimentary rocks which formed in a shallow sea about 75 million years ago. Late Cretaceous dinosaur fossils are known from one other locality on the Chatham Islands. Fragmentary theropod bones have been found in marine sedimentary rocks that are not older than 65 million years.

A turkey-sized dinosaur

In 1995 Brendan Hayes, a fossil collector, was walking along the coast near the Waikato River mouth when he found a small bone encased in rock. The rock revealed its secrets when he extracted the bone and had it examined. He had found New Zealand’s first Jurassic dinosaur bone – a finger bone from a small theropod dinosaur that was about the size of a turkey.

The dinosaurs’ demise

The most widespread explanation of the dinosaurs’ extinction 65 million years ago is a catastrophic meteorite impact. Estimated to have been 10 kilometres in diameter, the meteorite completely vaporised on impact. It gouged a 200-kilometre-wide crater on the northern Yucatan Peninsula in Mexico. From investigations of fossilised vegetation, scientists think it hit earth in July. The entire surface of the earth was plunged into darkness for at least three months because sunlight was not able to penetrate the resulting dust cloud. Paleontologists think all animals weighing more than about 20 kilograms perished. Smaller animals survived by hibernating, living underground, or living off reduced food supplies. Among the survivors were ancestors of modern mammals.


Age of mammals – Cenozoic

Zealandia, the New Zealand continent, broke away from Gondwana about 85 million years ago. As it did so, the floor of the Tasman Sea formed. Zealandia’s drift and the spreading of the Tasman Sea floor continued for some 20 million years.

Under water

As Zealandia drifted, it sank. This went on for 60 million years, until about 25 million years ago, it was almost totally underwater, and therefore almost all of New Zealand’s Cenozoic fossils are marine. The most commonly found New Zealand fossils, which people can stumble across in road cuttings, river beds, and along the sea shore, are fossil shells from marine molluscs.

Around 24 million years ago collisions began along the boundary of the Pacific and Australian plates. This process was responsible for the emergence of the New Zealand landmass and the modern land surface, and uplift is still happening.

The age of marine mammals

The last 65 million years, the Cenozoic, is referred to as the age of mammals – in the New Zealand context it is more accurately called the age of marine mammals.

New Zealand has a rich and diverse fossil record of marine mammals (mainly whales with some seals). Widespread limestone formations (32–22 million years ago [Ma]), especially in Canterbury and North Otago, have provided most whale fossils. Along with them are fossil penguin-like birds. So far no terrestrial mammal fossils have been found.

Cenozoic fossil-bearing sedimentary rocks drape the older Cretaceous land (145.5–65 Ma) like blankets on a bed. The oldest Cenozoic (65–23.8 Ma) fossils are shallow water shells, with deeper water forms appearing successively in younger rocks. Younger Cenozoic sediments are characterised by remarkably widespread limestone. So around 25 million years ago New Zealand was a huge underwater platform with perhaps a few small islands poking up above the waves.

Great, great white

The great white shark (Carcharodon carcharias) is the most feared predator in the sea, growing up to 7 metres long. Fossil teeth of a giant shark (Carcharodon megalodon), which lived from 1.6 to 25 million years ago, have been found in New Zealand. The largest fossil teeth are about the size of a person’s hand. Going by the size of its teeth, this shark would have been 13 metres in length.

Cenozoic fossils include many marine invertebrates. There are also cetaceans (whales), turtles, penguins, sharks and bony fish. New Zealand’s oldest whale fossils date from 40 million years ago. New Zealand has some of the oldest known early penguin-like bird fossils (55 Ma). The first fossil seals appear in the late Cenozoic period (23.8–0 Ma).

Swamps, coconuts and crocodiles

Coal deposits continued to form on land through the early Cenozoic period with associated wood, leaf, spore and pollen fossils. From about 24 million years ago as the land re-emerged, swamps established in low-lying areas (Southland, Waikato, and the King Country). When swamp deposits were buried they formed lignite (a poor-grade coal).

In other areas mountains were forming. Terrestrial plant fossils include wood, legumes, leaves, flowers, seeds, coconuts, pollen and spores. Miocene fossil-bearing sediments (23.8–5.3 Ma) are widespread. Fossils of freshwater crocodiles, birds, fish, crayfish and molluscs have also been unearthed from Miocene lake sediments in Central Otago. The climate was warmer at times during the early Miocene, with Eucalyptus and Casuarina appearing. Northland was almost tropical and a type of coconut palm (Cocos zeylandica) grew there.


Terrestrial fossils

Terrestrial fossils are the remains of plants and animals that lived on land. The best places to find them are in lake, swamp and river deposits. New Zealand has many terrestrial sedimentary rocks, but they are not as rich in fossils as marine sediments.

Coal deposits are widespread. These originate from wood and leaves that accumulated in swamps and forests between 70 and 45 million years ago (Ma). Younger lignite and lake sediments (20–10 Ma) also have fossils. Parts of fossil plants are well known from these rocks, especially wood, leaves, pollen and spores, along with rare fruits, seeds, flowers and resin (amber). Animal fossils other than freshwater and terrestrial molluscs are extremely rare.

New Zealand’s oldest terrestrial fossils

The oldest terrestrial animal fossil is Middle Triassic, about 245 million years old. This is a single fossil bone, from a large salamander-like amphibian collected from rocks in the Titirangi Stream, a tributary of Southland’s Mataura River.

The oldest leaf fossils are called Glossopteris. They are about 255 million years old. The oldest fossil pollen and spores, collected from the same rocks within Southland’s Wairaki Hills, are of similar age.

Fossils of insects, including beetles, are extremely rare, yet fragments attributed to insects are commonly found with fossil pollen and spores. New Zealand’s oldest beetle fossil is a 145-million-year-old wing case, collected near Port Waikato.

Dinosaurs

New Zealand dinosaur fossils are known from three localities, and are about 145, 75 and 65 million years old. Although dinosaurs lived exclusively on land, it is interesting to note that fossils have been unearthed from shallow sea sediments, not terrestrial (lake or river) sediments.

The 75-million-year-old dinosaurs are about 10 million years younger than the separation of Zealandia from Gondwana. Over 10 million years of isolation they must have evolved considerably from their original Gondwanan ancestors, making them distinctly Zealandian dinosaurs. Only fragmentary bone fossils have been found, so the detailed identity of these dinosaurs remains obscure.

Sauropods and theropods

New Zealand’s first dinosaur fossil was found by Joan Wiffen and her friends in the late 1970s. Identification of this first find, the tail vertebra of a theropod dinosaur, was confirmed in 1980 by Australian vertebrate paleontologist Ralph Molnar. After that, Joan Wiffen found other bones which showed that 75 million years ago a community of dinosaurs existed including sauropods, a theropod and armoured dinosaurs. At least six different species have been discovered in the Mangahouanga Stream, inland Hawke’s Bay.

Scientists know that dinosaurs and mammals lived alongside each other. If dinosaurs existed on Zealandia then it follows that other reptiles and mammals were also living there. However, so far no Mesozoic (251–65 Ma) mammal fossils have been found in New Zealand. It is probably only a matter of time before they are.

Other reptile fossils

Fragments of fossil crocodile bones and teeth have been found in at least one locality in Central Otago. These are 20–15 million years old. Turtle fossils are recorded from a number of localities, but so far there are no confirmed discoveries of fossil snakes. The fossil record of tuatara, lizards and frogs is surprisingly poor, with no fossils older than 2 million years.


Bird fossils

More than 30,000 years ago

The fossil record for birds for the past 30,000 years is exceptional, but before this date the record is patchy at best and non-existent at worst. Penguins aside, the oldest fossil bird found in New Zealand was an albatross, whose fossils have been found in Oligocene rocks, formed 33.7–23.8 million years ago. This extinct albatross, Manu antiquus, lived around our ancient coasts.

Birds such as false-toothed pelicans (pelicans with serrated beaks) appear rarely in Miocene siltstones (23.8–5.3 million years ago [Ma]) in North Canterbury, and bird footprints of Miocene age are also known from the northern South Island at Murchison and Manaroa, Pelorus Sound.

In Central Otago there are fossil records of water fowl, including ducks, geese and a host of other aquatic birds, preserved in Miocene lake sediments. Other fossils there include masses of freshwater fish bones.

Shearwaters and false-toothed pelicans have also been unearthed from Pliocene rocks (5.3–1.81 Ma). The Pleistocene epoch, the record of the past 1.8 million years, has a better bird fossil record than previous periods but is still poor. Only a few moa fossils up to 2 million years old have been found.

The last 30,000 years

Peat, swamp, dune and cave deposits mostly less than 30,000 years old have produced a wealth of bones from birds, many of which are now extinct. Included in this fossil record are moa, kiwi, various water birds, huge eagles, rails, shorebirds, parrots, passerines and oceanic birds that nested ashore. This record began to be unearthed from about 1850, when the scientific world was astounded by huge moa leg bones pulled out of swamps, dunes, caves and river gravels in New Zealand.

Moa

In England in 1839, naturalist Richard Owen identified a bone fragment brought to him from the North Island’s East Coast as belonging to a huge bird, the moa. Other Europeans such as Walter Mantell, who arrived in New Zealand in 1840, were also fascinated by the fossilised bones of this extinct bird and collected moa bones wherever they travelled. Mantell bemoaned the Māori custom of smashing the bones unearthed by erosion.

The founder of Canterbury Museum, Julius Haast, collected many moa bones and published papers on his discoveries. Most of these early finds came from dunes, swamps, Māori middens (rubbish heaps) and caves. In Central Otago, caves containing mummified moa with preserved soft tissue were found. Throughout the country caves revealed the fossil bones of many other extinct birds.

Research

New Zealand’s exceptional recent fossil record has allowed modern researchers such as Richard Holdaway and Trevor Worthy to show that a number of birds became extinct about the same time as humans arrived. Radiocarbon dates obtained from fossils from archaeological sites have estimated the timing of Polynesian arrival in New Zealand to 1250–1300 AD.

The fossil record has also allowed many bird species to be studied in detail. In many cases this has allowed evolutionary links to be made between many of New Zealand’s living and extinct bird species.


Microfossils

Microfossils are the remains of tiny animals and plants found in rocks and sediment. They are very small and can be measured in millimetres (most are smaller than a pinhead). Scientists use microscopes to study them. Most of the paleontologists (geologists who study fossils) working in New Zealand study microfossils. The reason for this is that they are the most common fossils in marine sediments. The organisms that grow these tiny skeletons evolve rapidly, are incredibly prolific, and are widespread. Scientists use these fossils to establish where oil and gas may be found, and for studying past environments and climates.

There are different groups of microfossils. Pollen and spores are examples of terrestrial microfossils. Common marine microfossils include foraminifera, dinoflagellates and radiolarians.

Foraminifera

Foraminifera are single-celled animals (protozoa) composed of a jelly-like mass encased in a calcareous shell. They live in diverse environments, from the sea floor to the surface waters. Those that live in surface waters are most abundant in the open ocean. As they and other tiny organisms die, their minute shells slowly rain down to the ocean floor. Near to land, sediment washing into the sea from the land mixes with the tiny shells. The resulting sandstones and mudstones contain microfossils. Far away from land, the sea-floor sediments are composed almost entirely of these tiny skeletons.

Foraminifera have evolved rapidly and can therefore be used to determine the relative age of rocks. Any core of rock drilled from the sea floor contains a sequential record. As they are small and numerous, microfossils can easily be extracted from rock cores and used to identify which sediment layer the drill is passing through. This makes them important for geologists mapping geological structures and identifying different layers of sedimentary rock, some of which may contain oil and gas. Changes in the types of microfossils found in sedimentary rocks indicate past changes in conditions.

More recent microfossils, such as modern foraminifera, deposited in sands and mud, are being used by researchers in Auckland’s Waitematā Harbour as indicators of changes in the coastal environment.

Radiolarians

Radiolarians are single-celled organisms with silica shells that float about in the world’s oceans. They have an evolutionary history dating back 500 million years. Scientists studying radiolarians look at when individual species first appear and then became extinct. They have used this information to date some of New Zealand’s oldest rocks. The evolution of radiolarians also helps scientists to understand changes in ocean conditions over millions of years.

Pollen and spores

Seed-bearing plants propagate themselves by releasing massive amounts of pollen, while lower plants such as ferns release spores. Pollen and spores are widely broadcast in the air and settle onto the earth everywhere. They are often well preserved in swamp deposits and lake sediments. Fossil pollen and spores are used to study past climates and vegetation patterns. This is possible as different plants have distinct types of pollen and spores. The relative abundance of different pollen and spores reveals what types of vegetation grew at a particular time and also what the climate was like.

By comparing the quantity of different pollen types preserved in swamp sediments scientists have concluded that widespread burning of forests first occurred in New Zealand around 1300 AD. This is one of the strands of evidence that points to Polynesian settlement of New Zealand occurring about 1250–1300 AD.


Uses and collections

For many people fossils are intriguing and beautiful objects. They are collected because of their shape, texture or colour.

Serving science and industry

To geologists fossils help solve problems about origins, age and relationships of sedimentary rock layers. To paleontologists they are a history of life, showing what previous organisms looked like and how they functioned and evolved. To geochemists, fossils are time capsules. Some fossils provide stable isotopes of oxygen, carbon and strontium, which provide insights into what past climates and environments were like, and how extinctions occurred.

Some rocks such as limestone are almost entirely made up of fossils. Limestone is a biogenic rock – it has formed from the skeletal remains of once-living creatures. Limestone is used to make cement, for building (such as Ōamaru stone), and is also crushed and applied to farmland as fertiliser.

Pollen, along with sand grains and organic debris found at crime scenes, in car mudguards or clothing is used by the police in forensic work, as different localities have unique pollen profiles due to the particular mix of plants that grow there.

Fossil fuels

Coal is another biogenic rock. Originally it accumulated as plant material in swamps and forests, before being buried. Oil and gas are derived from the slow pressure-cooking of organic matter buried at great depths (normally more than 5 kilometres).

Underground exploration for oil, gas, coal or water makes use of microfossils. As they provide information on the age, origins and relationships of rock layers they provide geologists with clues as to where coal, oil or gas is likely to be found – usually porous rocks that were once coastal sands.

Fossil hunters

Paleontologists are trained fossil hunters. Subtle features on rock surfaces, changes in texture or colour, or strange shapes attract their eye. Most collecting requires only keen eyes, a geological hammer and a cold chisel. Collectors rarely dig with spades, unless sediments are exceptionally soft. In New Zealand such sediments would usually be very young (formed less than 2 million years ago). Bigger fossils require more equipment – for large vertebrate fossils (dinosaurs and whales), power tools and heavy machinery are often needed.

Location and scientific discovery

In 1946 geologist Harold Wellman established the Fossil Record File – a New Zealand-wide register of fossil localities recorded by members of the geological community. The only national database of fossil localities in the world, it is now administered by the Geological Society of New Zealand.

Serious collectors carry notebooks to record new localities, preferably using a Global Positioning System (GPS) instrument. Very precise details are also required of the actual rock layer that holds the fossils. Each fossil is unique. Once collected, fossils are carefully wrapped in newspaper and placed in labelled bags. A small, sturdy backpack is used to carry fossils back to the car.

Collections

GNS Science, at Avalon in the Hutt Valley, holds the national paleontology collection, the country’s largest. Other major collections are held at universities, museums, and by private collectors. Otago Museum has the largest public exhibit of New Zealand fossils, and the University of Otago’s geology department museum the second largest.

Where to collect fossils

The best places to look for fossils are along shore platforms and coastal cliffs where there are outcrops of sedimentary rock. Most shorelines are publicly accessible and are open to collecting. Exceptions are beaches within National Parks, Department of Conservation reserves, land owned by Māori tribes, land designated as Geological Reserves and private land. It is essential to check the tides and watch out for waves when collecting on the coast.

Coastal and river valley exposures of fossil-bearing rock are constantly eroded by wind, sand and water. If visible fossils are not collected, then nature will slowly destroy them.

Acknowledgements to Richard Cook (GNS Science)


External links and sources

More suggestions and sources

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How to cite this page: Hamish Campbell, 'Fossils', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/en/fossils/print (accessed 28 June 2019)

Story by Hamish Campbell, published 12 Jun 2006