This exquisitely preserved fish was found—perfectly filleted—when scientists split a block of Foulden Maar diatomite in half. They named it Galaxias effusus, and it is the oldest known relative of the galaxiid freshwater fish that still swim in New Zealand creeks and rivers today. Credit: Kate Evans
Scientific American has a story about a fossil deposit in New Zealand. The deposit formed around a shallow-sided volcanic crater about 23 million years ago during the Miocene epoch. This site is about an hour's drive from the city of Dunedin in New Zealand. There are fossils of plants and animals and the preservation is stunning.
For at least 120,000 years, a rain forest grew around the lake. In its waters, tiny single-celled algae called diatoms bloomed each spring and summer and then died and sank to the bottom. “The diatoms are the most important fossils in a way, because without them, we wouldn't have the other things preserved,” says Daphne Lee, a geologist at the University of Otago in New Zealand, who has led scientific excavations at Foulden Maar for nearly two decades.
And those other fossil plants and animals are sensational. Lee and her colleagues unearthed an entire ecosystem, perfectly captured in the powdery diatomite rock: spiders, dragonflies, fruits, flowers complete with pollen grains resting on their petals, fish with scalloped scales, intricate termite wings, the hexagonal lattice of a fly’s compound eyes, and iridescent beetles still glistening in green, copper and bronze.
Most frequently of all, they found leaves—so delicately pressed that climate scientists could analyze their structure and chemical composition to discover that atmospheric carbon dioxide in the early Miocene reached 550 parts per million, levels similar to those predicted for Earth by 2050.
