stromatolites

The Archean World, Peter Sawyer, The Smithsonian Institution

In the Archean, life is at its purest. No courtship, no conflict, no sleep, no song, no fear, no lust—just organisms, simplified to abstraction, thriving in poison, water, and ash. Life is not a substance, but a process: consume and continue.

Thermophiliacs feast on hot spring chemicals, relishing the heavy stink of sulphur, and kaleidoscope the steaming pool’s edges. Elsewhere, stromatolites, shallow-water plateaus of sediment and biofilm, learn photosynthesis, change the atmosphere, and terraform the dawn planet. 

The microbes are oblivious to anything outside of their own homeostasis, yet assemble into communities, unknowingly nestling cell walls against each other. Millions of lives surround each bacteria, but they only know their own, like a man running through the streets of Prague, bumping elbows with a thousand other lives—each rich with hope and love and loss—but thinking only of catching the 207 bus on time.

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3.7 billion-year-old fossil found in Greenland may be the oldest sign of life

Fossils found on the coast of Greenland may be the oldest signs of life ever discovered, dating back 3.7 billion years. The stromatolites, fossils formed from ancient biomaterials called microbial mats, were found in Isua, a remote part of Greenland known for it’s absurdly old belt of rock formations. The finding may have implications out in the solar system too.

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Stromatolite layers

Since before the boring billion (as geologists jokingly call it, roughly 2-1 billion years ago), the main complex form of life consisted of microbial communities organised in mats that grew upwards, incorporating sediment from the surrounding sea. Made up of many kinds of bacteria and archaea, they form a layered community with aerobic bacteria at the surface and anaerobic ones feeding off their waste products below. Each layer of life ends up buried in the incorporated sediment, leading to a fresh one developing anew above. They still exist today in marginal brackish environments such as shark bay in Western Australia. In this stunning example (38,5x31x2,5 cm) found near Cochabamba in Bolivia, the layering that marks these communities has been beautifully picked out. We shared some time ago another example, replaced with red jasper (a mixture of silica and iron oxide rich mud) known as Mary Ellen jasper (see http://on.fb.me/1OCAiuq)

Loz

Image credit: Didier Descouens

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Bitter Springs Dolomites Jul14

Chert nodules cross bedding and stromatolites preserved in limestones of the Bitter Springs Formation, central Australia.

The hills in the foreground of the last photo display well developed formlines of outcropping Bitter Springs strata in Trephina Gorge National Park.

The Bitter Springs Formation is an 850 million year old sequence of Precambrian limestones and dolomites. 

Dissolution weathering makes for some very sharp outcrops (2/10 would not recommend falling over hands first, I still have the scar).

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First Life sees Attenborough tackle the subject of the origin of life on Earth. He investigates the evidence from the earliest fossils, which suggest that complex animals first appeared in the oceans around 500 million years ago, an event known as the Cambrian Explosion. Trace fossils of multicellular organisms from an even earlier period, the Ediacaran biota, are also examined. The naturalist travels to Canada, Morocco and Australia, using some of the latest fossil discoveries and their nearest equivalents amongst living species to reveal what life may have been like at that time. Visual effects and computer animation are used to reconstruct and animate the extinct life forms.

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Photos I took of the Stromatolites, Lake Thetis.

“Stromatolites provide some of the most ancient records of life on Earth by fossil remains which date from more than 3.5 billion years ago.”

Info board:

“The rock-like platforms and domes in front of you are both stromatolites but they are built by different types of cyanobacteria, hence their different shapes. As the cynobacteria grow upwards, their activities bind calcium carbonate onto the growing surface. Lake conditions are 1.5 times saltier than the ocean, supporting very few predators thus allowing the microbial communities to survive thousands of years. Dark areas on the platforms and domes indicate wet, active growth of cyanobacteria, which continue constructing the stromatolites.”