Life in maars: why it’s worth protecting this spectacular fossil site
What are the next steps in the Foulden Maa r saga?
This article has been republished from The Conversation under Creative Commons licence CC BY-ND 4.0 and is written by John G Conran (Senior Lecturer in Evolutionary Biolo gy, University of Adelaide), Daphne Lee, (Honorary Associate Professor in Geology/Paleontology, University of Otago) and Uwe Kaulfuss, (Geologist (PhD ), Georg-August-Universität Göttingen). It was originally published under the title ‘Life in maars: why it’s worth protecting a spectacular fossil site NZ almost lost to commercial mining interests’.
Well preserved fossil
Folden Maar and Hindon Maar fossils include an unusual depth of detail – as shown by the gaping mouth and large eye of this whitebait specimen.
One of New Zealand’s most exceptional fossil sites may soon be open to scientists again following a land purchase that saved it from commercial mining.
Foulden Maar is a small, deep lake that formed 23 million years ago in Otago, at the start of the Miocene epoch when New Zealand’s climate was much warmer and wetter. A rainforest thrived around the lake’s fringes, and algae known as diatoms bloomed each summer.
As the algal blooms died off and sank to the lake bed, they formed sedimentary layers of diatomite and preserved the most exquisite and delicate fossils of flowers, insects and fish as well as a climate record covering 100,000 years.
But the diatomite was also of interest to mining company Plaman Resources – until, following long negotiations, the Dunedin City Council bought most of the land earlier this year.
Fossil sites are relatively common, but examples representing entire ecosystems are extremely rare. Foulden Maa r is one of only two such sites in New Zealand that preserve ecological interactions and features such as eyes, skin, stomach contents and original colour patterns.
A galaxiid fish fossil
The diatomite at Foulden Maar preserved fossils, such as this galaxiid fish, in delicate detail.
Such sites yield remarkable information about the history of life, which is impossible to obtain from other sources.
The other site is the nearby Hindon Maa r complex, which is 15 million years old. Both sites preserve ecosystems of small crater lakes and the animals and plants of surrounding rainforests. Recent discoveries at these sites are transforming our understanding of New Zealand’s past biodiversity and climate.
Lake ecosystems: freshwater galaxiids and eels
All fossils of the iconic southern-hemisphere family Galaxiidae derive from Otago Miocene lake deposits, with the entire life cycle from larvae (whitebait) to juveniles and fully grown adults present at Foulden Maar .
Remarkable preservation of numerous articulated skeletons includes eyes, gaping mouths and skin, the last including the star-like patterning that gave galaxiids their name.
Colourful fossils
Some galaxiid fossils still show the colour and patterning of skin.
Gut contents and an abundance of fossilised poo (coprolites) provide evidence of a changing diet. Larvae dined on diatoms while adults were lake-margin ambush predators feeding on terrestrial and aquatic insects. Fish debris in other less common coprolites show the galaxiids were themselves prey.
Slender, elongated articulated fish skeletons with rows of curved conical teeth provide the only southern-hemisphere records of the freshwater eel, Anguilla. This was likely the top predator in these lakes.
Freshwater eel fossil
A fossil from Hindon Maar shows skeletal details of the freshwater eel Anguilla.
Trapped in these small, closed lakes, the eels would have been unable to return to the sea to breed and were effectively “living dead”, unlike the galaxiids which could reproduce in the maars.
Weevil fossil
Otago’s maar lakes are a treasure trove of insect fossils, such as this weevil.
Forest ecosystems: insects, spiders, leaves, flowers
These ancient maar lakes also contain a treasure trove of spiders and insects. When our research programme began in 2003, only six fossil insects more than two million years old were known from New Zealand. We now have more than 600, almost all different.
Foulden Maar has yielded 270 insects from 17 genera in 15 families and nine orders.
Fossilised spider
It is rare to find fossilised spiders because they lack hard parts.
Spiders are commonly the top terrestrial invertebrate predators in modern New Zealand forests, but rarely fossilise because they lack hard parts. But in Foulden Maar, we found several specimens, including a juvenile trapdoor spider.
Early studies at Hindon Maar have already added 240 more insects in five orders and 20 families.
Insects are often completely preserved with details of antennae, fragile wings and compound eyes visible.
Fossils from the Foulden and Hindon maars include ancient lineages of termites, armoured scale insects in life position along leaf veins , bark bugs and a lace bug that probably lived on Astelia (kakaha, bush lily) as its close living relative does today.
Others include leaf beetles with structural colour, weevils, rove beetles, numerous ants and wasps, caddis flies with larvae still in their cases, crane flies with well preserved compound eyes and a hairy cicada whose closest relative today is found in Tasmania.
Fossilised cicada wing
Delicate detail of a fossilised cicada wing.
These taxa are only the tip of the taxonomic iceberg. Hundreds more terrestrial arthropods are also being revealed in our research on inclusions in New Zealand amber – 90 specimens in one block of layered amber alone.
Rainforest leaves and flowers
Myriad leaves with excellent preservation show that both maars were surrounded by subtropical to warm, temperate rainforests, dominated by members of the laurel and cinnamon plant families at Foulden Maar and a southern beech forest at Hindon.
Fossilised leaves
Fossilised leaves show that both maars were surrounded by rainforests.
To date we have recorded at least 100 species from 35 plant families between the sites, including many taxa now extinct locally, but with relatives still living in New Caledonia, Australia and South America.
Of particular importance are diverse fossil flowers with reproductive structures such as petals, stamens and anthers with pollen still present, as well as abundant fossilised fruits and seeds.
These reproductive structures are treasures of a different kind – fragile, seasonal and fleeting. But they provide critical information about the ecology of the parent plants and their possible pollination and dispersal mechanisms.
A fossil flower
Fossil flowers provide information about ancient plants’ pollination and dispersal.
Close comparisons to the biology of living plants also suggest the fossil species reproduced in a similar manner to their living relatives. This implies that reproductive mechanisms were conserved for 23 million years in the New Zealand flora.
Currently, the Dunedin City Council is exploring management options for the site, which will once again allow public and scientific access to this remarkable fossil-rich, ancient lake deposit well into the future.
Related content
Learn more about the ancient fossils of Foulden Maar and the fight to protect the site from mining. There are also lots of useful links at the bottom of this article.
The Connected article Foulden Maar: fossils or food? prompts critical thinking and ends with a call to social action.
Learn about the formation of maars in Auckland’s volcanoes.
Find out about some of the different ways scientists date fossils in Dating the past – introduction and Date a dinosaur.
To follow media articles and reports on Foulden Maar, go to our Pinterest board.
Paleoclimatology
Foulden Maar has been used in research around past climates. Learn more about this field – paleoclimatology – in Clues to the past, Carbon dioxide and climate and the video Fossil plants as paleoclimate proxies.
Students can take part in a citizen science project, Fossil Atmospheres. The project is comparing some features of fossilised plants with the same features of plants living today to learn more about the effect of changing carbon dioxide (CO2) levels in our atmosphere.
Activity idea
Useful links
Find out more about some of the research mentioned in this article:
In January 2023 Dunedin City Council announced that it had reached an agreement to buy the Foulden Maar mining site. Read this RadioNZ news story.
Read about how Exquisite fossils show an entire rainforest ecosystem on the Scientific American website.
This The Conversation article looks at how New Zealand’s fossil record suggests more species lived in warmer waters. But the current rate of warming may break this pattern.
In this The Conversation article, explore whether New Zealand should celebrate its remarkable prehistoric past with national fossil emblems – have your say!
Find out more about the Astelia fragrans (Kakaha, Bush Lily) on the Goughs Nurseries website.
Kaulfuss U, Lee DE, Robinson JH, Wallis GP, Schwarzhans WW. A Review of Galaxias (Galaxiidae) Fossils from the Southern Hemisphere. Diversity. 2020; 12(5):208. https://doi.org/10.3390/d12050208.
Lee, D E., Kaulfuss, U., Conran, J G., Bannister J M., Lindqvist, J K. Biodiversity and palaeoecology of Foulden Maar: an early Miocene Konservat-Lagerstätte deposit in southern New Zealand. Alcheringa: An Australasian Journal of Palaeontology, 40, 2016 - Issue 4. https://doi.org/10.1080/03115518.2016.1206321.
Kaulfuss, U., Lee, D E., Wartho J., et al. Gy and palaeontology of the Hindon Maar Complex: A Miocene terrestrial fossil Lagerstätte in southern New Zealand, Palaeogeography, Palaeoclimatology, Palaeoecology, e 500, 2018, https://doi.org/10.1016/j.palaeo.2018.03.022.
Kaulfuss U., Bannister J M., Conran, J G., et al. Review of flowers and inflorescences with in situ pollen from the Miocene Foulden and Hindon Konservat-Lagerstätten, southern New Zealand. Review of Palaeobotany and Palynology, e 311, April 2023, https://doi.org/10.1016/j.revpalbo.2022.104830.
Additional links
See the Building Science Concepts, Book 41: Fossils: Digging up the Past to extend your students’ understanding about fossilisation and the insights we can gain from fossils.
Acknowledgements
The Conversation
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