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The discovery in Morocco drew attention because the wrinkled structures were preserved in deep-water sediments, without sunlight, where delicate marks made by microbes would not normally be expected. The finding may expand the search for clues of ancient microbial ecosystems on Earth.
The discovery of ancient life marks in Moroccan rocks drew attention for appearing in an unlikely environment: deep-water sediments, where sunlight does not reach and where delicate structures are usually destroyed.
Dr. Rowan Martindale, from the University of Texas at Austin, was exploring the region, in the local landscape, with researchers, including Stéphane Bodin, from Aarhus University.
The team was investigating ancient reef ecosystems of an ocean that covered that area. To reach them, they crossed turbidites, rocks formed by underwater avalanches of mud, sand, and debris.
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Wrinkled structures raised the alarm
Ripple marks are common in turbidites. What surprised Martindale was the unusual appearance of a wavy plane. Upon closer observation, she identified wrinkled structures preserved in the rock.
These wrinkles are ridges and depressions formed when microbial communities grow over sandy sediments. The mats bind the sediment and leave distinct textures, useful for studying traces of ancient microbial life.
These structures are usually fragile. When animals began to burrow into seafloor sediments, many delicate marks were erased before preservation.
Therefore, wrinkled structures are uncommon in rocks less than 540 million years old and appear more associated with shallow coastal environments.
Why ancient life appeared in an unlikely place
The analyzed rocks posed a puzzle. The turbidites with the wrinkles were formed in deep waters, at least 180 meters below the ocean surface. At this depth, sunlight does not penetrate.
If photosynthesis-dependent algae could not have produced the structures, another explanation was needed. The mystery deepened because the sediments were approximately 180 million years old.
The activity of these animals would normally churn the sediment and destroy fragile textures. Everything in that context indicated that the wrinkles should not have been preserved there.
Martindale highlighted the need to gather evidence to confirm that these were wrinkled structures in turbidites. The team analyzed the layers and looked for chemical signs linked to the action of living organisms.
Carbon and microbes help explain the wrinkles
The investigation found high concentrations of carbon in the layers below the wrinkles. This enrichment is usually associated with biological activity and strengthened the hypothesis of microbial involvement.
The researchers compared the case with modern oceans. Images obtained by remotely operated submersibles show that microbial mats can exist below the photic zone, the illuminated layer where photosynthesis occurs.
In these dark regions, microbial communities can be sustained by chemosynthetic bacteria. These organisms obtain energy through chemical reactions, using hydrogen sulfide or methane, instead of sunlight.
By combining geological, chemical data, and modern observations, the researchers concluded that the structures could be chemosynthetic wrinkles preserved in the rock record.
Discovery may expand the search for microbial signs
The proposed explanation indicates that turbidite flows brought nutrients and organic matter to the seabed. With the decomposition of this material, oxygen in the sediment decreased, creating favorable conditions for chemosynthetic microbes.
In the intervals between new debris flows, bacterial mats could spread over the surface. In specific situations, these textures would have been quickly buried and preserved for millions of years.
The discovery suggests that deep waters, previously seen as unlikely for this type of evidence, may hold clues about ancient microbial ecosystems. Martindale hopes that laboratory experiments will help understand this process.
What do you think about this discovery in Morocco and the possibility that signs of ancient life are hidden in deep, dark, and previously considered unlikely environments? Share your opinion and say if this type of research changes your way of imagining where science should look for clues about Earth’s past.
The study is available at geoscienceworld.
