PaleobiologyAustralia

850-Million-Year-Old Cells Dividing

Australian rocks containing fossils of cells frozen in the act of dividing 850 million years ago. These are the oldest known examples of complex cell division, capturing the moment when life figured out how to reproduce in the way that made multicellular organisms possible.

A Snapshot of Ancient Reproduction

In the arid landscapes of central Australia lies the Bitter Springs Formation, a geological deposit holding secrets from the deep past. The formation is a layer-cake of dolomite, limestone, and chert dating to the Neoproterozoic Era, roughly 850 million years ago. It is most famous for its microfossils, which are exceptionally preserved in the dark chert. These chert nodules effectively created natural microscope slides, trapping and preserving single-celled organisms in three-dimensional detail.

The initial discoveries were made in 1965, revealing a diverse community of what appeared to be bacteria, fungi, and different types of algae. Among the most significant finds are specimens of a green alga named Glenobotrydion. These microscopic spheres, only tens of micrometers in diameter, show clear evidence of cells in various stages of division. The fossils capture cell nuclei dividing in a process that is structurally consistent with meiosis, the method of cell division that produces gametes (sex cells) in modern plants and animals. This discovery provides some of the oldest direct fossil evidence for the complex cellular mechanics that underpin sexual reproduction. Before this, life largely replicated through simple cloning. The evolution of meiosis was a prerequisite for the genetic variation that allowed for the development of complex, multicellular life.

The World of Bitter Springs

The Bitter Springs Formation is part of the much larger Amadeus Basin, a 170,000-square-kilometer intracratonic sedimentary basin. During the Tonian Period (1,000 to 720 million years ago), this region was a shallow, saline sea on the supercontinent of Rodinia. The environment was likely a series of nonmarine saline lakes and ponds. The water was hypersaline, which "pickled" the microorganisms, preventing their immediate decay after death. This high-salt environment, saturated with silica, allowed for the formation of the chert that would entomb and preserve these ancient cells.

The ecosystem captured in the fossils was complex. Alongside the eukaryotes like Glenobotrydion, the formation preserves numerous stromatolites—layered structures built by colonies of cyanobacteria. Two notable species are Linella avis and Inzeria intia. The presence of these photosynthetic bacteria indicates that the shallow waters were a sunlit, productive environment. The Bitter Springs fossils, taken together, show a microbial world that was already ancient and diverse, led to for the later explosion of animal life in the Ediacaran and Cambrian periods.

💡Fun Facts

The Bitter Springs microfossil assemblage was first described in detail by paleontologist J. William Schopf in 1968.
The formation's rock layers are part of the Centralian Superbasin, a vast geological province that existed across much of Australia during the Neoproterozoic.
The Amadeus Basin, where the formation is located, today contains vast salt lakes, like Lake Amadeus, which holds an estimated 600 million tons of salt.
The rock is primarily dolomite, a carbonate rock, with lenses of black chert that contain the well-preserved microfossils.

References

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Practical Information

Opening Hours: This is a remote, unfenced geological area with no official hours.
Admission: Free.
Accessibility: The Bitter Springs Formation outcrops are in remote, rugged terrain within the Amadeus Basin. Access requires a 4x4 vehicle, and visitors must be entirely self-sufficient with water, fuel, and emergency supplies. Outcrops can be poor and heavily masked by calcrete.

The Bitter Springs FormationNorthern Territory, Australia

More in Australia Explore on the map →

PaleobiologyAustralia

850-Million-Year-Old Cells Dividing

A Snapshot of Ancient Reproduction

The World of Bitter Springs

💡Fun Facts

The Bitter Springs microfossil assemblage was first described in detail by paleontologist J. William Schopf in 1968.
The formation's rock layers are part of the Centralian Superbasin, a vast geological province that existed across much of Australia during the Neoproterozoic.
The Amadeus Basin, where the formation is located, today contains vast salt lakes, like Lake Amadeus, which holds an estimated 600 million tons of salt.
The rock is primarily dolomite, a carbonate rock, with lenses of black chert that contain the well-preserved microfossils.

References

There's more in the app

3000+ curious places on an interactive world map, free on Android.

Read offline — articles and maps work without a connection
Save places and build trip collections
Daily discovery — one fascinating place a day

Get it on Google Play

Practical Information

Opening Hours: This is a remote, unfenced geological area with no official hours.
Admission: Free.
Accessibility: The Bitter Springs Formation outcrops are in remote, rugged terrain within the Amadeus Basin. Access requires a 4x4 vehicle, and visitors must be entirely self-sufficient with water, fuel, and emergency supplies. Outcrops can be poor and heavily masked by calcrete.

The Bitter Springs FormationNorthern Territory, Australia

More in Australia Explore on the map →

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