Those faint, crinkled patterns, stamped into slabs of ancient sandstone and siltstone, have turned out to be the remains of deep-sea microbial communities that should, by all accounts, have been impossible where they formed.
Ancient wrinkles in the wrong place
The odd fossil textures were found in the Central High Atlas, in Morocco’s Dadès Valley, inside rock layers known as the Tagoudite Formation. They date back around 180 million years, to the Jurassic period.
Lead researcher Rowan Martindale, a geobiologist at the University of Texas at Austin, was there to study old reef systems. While walking across the outcrop, she noticed the ground under her boots looked subtly corrugated, almost like a frozen fabric of ripples and folds.
These “wrinkle structures” are typically linked to microbial mats in shallow, sunlit water — not the dark depths of the ancient seafloor.
That mismatch is what makes the find so surprising. The rocks that host the wrinkles are turbidites. These are deposits left behind by underwater landslides, rapid slurries of mud and sand that race down the continental slope.
Geological analysis shows these sediments were laid down at least 180 metres (about 590 feet) below the sea surface. At that depth, very little light would have reached the seafloor.
What are wrinkle structures, and why do they matter?
Wrinkle structures are subtle, wavy patterns on the surfaces of ancient sediments. They usually form when sticky microbial mats drape across soft mud or sand and interact with currents, waves or settling particles.
These mats are made of layered communities of microbes that trap and bind grains. Over time, the mats and the textures they create can be buried and turned into stone.
Wrinkle structures are widely viewed as one of the key clues for tracking very early life on Earth, especially before animals became abundant.
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Most well-known wrinkle structures come from rocks older than 540 million years, before burrowing animals were common. Once worms, crustaceans and other creatures began churning up seafloor sediment, the delicate microbial textures were often erased.
Finding such clear structures in Jurassic-age rocks is already unusual. Finding them in deep-water turbidites is stranger still.
Too dark for sunlight, so life turned to chemicals
The first question for the team: if there was no meaningful sunlight, how did these microbial communities get their energy? The shapes in the rock looked similar to mats made by photosynthetic microbes, but the setting did not fit that picture.
Chemical tests brought the answer into focus. The wrinkle-bearing layers contained elevated carbon, a signal strongly associated with biological activity. Yet there was no sign that sunlight had been a major energy source.
The researchers concluded the ancient microbes were chemosynthetic, living off chemical reactions rather than light.
Chemosynthetic organisms harness energy by oxidising chemicals such as hydrogen sulfide, methane or reduced iron. Today, such communities thrive around hydrothermal vents, cold seeps and certain parts of continental margins.
In this Jurassic setting, the likely fuel came from the landslides themselves. Each underwater avalanche would have dragged organic material from the shallower shelf into deeper water. As that organic matter decayed, it would have released compounds that chemosynthetic microbes could use.
How underwater landslides fed the mats
The study proposes a repeating cycle on the ancient seafloor:
- Landslides swept sediment and organic debris down the slope, forming fresh turbidite beds.
- Organic material in those beds broke down, generating methane and hydrogen sulfide.
- Chemosynthetic microbial mats colonised the surface, feeding on those chemicals.
- Later landslides sometimes buried or ripped up the mats, preserving wrinkle textures in the process.
Not every event would have left fossils. Many mats were likely destroyed without trace. The ones preserved as wrinkle structures are snapshots of a much longer-lived deep-sea ecosystem.
Rethinking where early life might be preserved
The presence of chemosynthetic wrinkle structures in deep-water turbidites challenges long-standing assumptions about where scientists should look for early traces of life.
The work suggests that geologists have been overly focused on shallow, calm settings, ignoring vast areas of the ancient seafloor where life may also have flourished.
If microbial mats could colonise chemically rich turbidites in the Jurassic, similar communities may have existed much earlier in Earth’s history. Those older deep-water rocks have not always been searched carefully for such subtle structures.
By extending the hunt into deeper, more unstable environments, researchers might uncover wrinkle structures that push back the record of complex microbial communities, especially those powered by chemistry rather than light.
Why chemosynthesis matters for life’s story
Chemosynthesis is central to debates about how life began. Many origin-of-life scenarios place the first ecosystems in environments rich in chemical energy but poor in light, such as hydrothermal vent systems.
The Moroccan wrinkles don’t mark the beginning of life, but they show that chemosynthetic communities were thriving in deep marine settings long after photosynthesis had transformed the planet. That raises a key point: multiple energy strategies can coexist for vast stretches of time.
| Energy source | Typical modern setting | Relevance to the Moroccan find |
|---|---|---|
| Sunlight (photosynthesis) | Shallow seas, lakes, land plants | Unlikely at 180 m depth, given weak light |
| Chemicals (chemosynthesis) | Vents, seeps, some continental margins | Best explanation for the deep-water microbial mats |
| Organic decay (heterotrophy) | Most ecosystems | Decomposed material provided chemical fuel for chemosynthetic microbes |
What this means for Mars and other worlds
Findings like these also shape how scientists think about life beyond Earth. Many planetary bodies, including Mars and icy moons like Europa and Enceladus, may have or once had dark, subsurface or underwater environments with chemical energy but little or no sunlight.
The Moroccan deep-water mats show that life can organise itself into stable, layered communities in such conditions, leaving fine-scale textures behind. That raises the possibility that rocky records on Mars, especially in ancient basins where sediment slumped downslope, could host wrinkle-like imprints formed without any need for sunlight.
Key terms and how to picture them
Some of the jargon in this research sounds abstract, but the concepts are easier to grasp with simple comparisons:
- Microbial mat – imagine a thin, living carpet on the seafloor, made of billions of tiny microbes glued together with slime.
- Turbidite – think of a muddy avalanche racing down a submarine canyon, then settling out to form a layered blanket of sand and silt.
- Chemosynthesis – instead of plants using light to make sugars, microbes use chemicals like hydrogen sulfide as their power source.
On a modern continental shelf, if you could scrape away the overlying water, you might see dark, patchy mats clinging to oxygen-poor spots where decaying matter releases chemicals. The Jurassic seafloor in Morocco likely looked similar at times, only to be periodically buried by fresh submarine landslides.
Where scientists might look next
Geologists are now likely to revisit deep-marine rock formations that were once written off as too disturbed or too dark for preserving subtle biosignatures. Steep continental margins, ancient slope basins and older turbidite systems are all candidates.
Future work may pair high-resolution imaging with geochemical tests to separate truly biological wrinkle textures from purely physical ripples and scrapes. If more examples appear in older rocks, they could reshape timelines for when chemosynthetic ecosystems became widespread.
For students or readers keen to spot these features on field trips, the key is restraint. Wrinkle structures are often delicate, low-relief and only obvious when the light hits at a shallow angle. Many have probably been walked across for decades without anyone realising they recorded ancient microbial life quietly thriving in the dark.