Deepwater rock wrinkles likely formed from chemosynthetic microbes, not just physical processes, reshaping assumptions about ancient ecosystems.
In 2016, geologist Rowan Martindale was hiking on a hillside in Morocco when she noticed something unusual: a slab of sedimentary rock marked by a wrinkled surface that resembled elephant skin.
“I looked at the wrinkles, and I was like, ‘These aren’t supposed to be in rocks like this. What the heck is going on?’” said Martindale, an associate professor at The University of Texas at Austin’s Jackson School of Geosciences.
Rock textures can reveal the processes that shaped them over time. To Martindale, the patterns looked like classic microbial mat fossils, preserving a dense community of bacteria that lived more than 180 million years ago during the Early Jurassic.
Microbial Fossils in an Unexpected Setting
During graduate school, she had seen many examples of similar textures through photos and samples, thanks to a colleague who studied Early Triassic microbial fossils.
But there was a major inconsistency: the surrounding geology did not match expectations.
The sediment containing the wrinkles came from a deep ocean environment, roughly 600 feet (about 183 meters) below the surface. However, scientists have generally believed that microbial wrinkle structures form only in shallow waters under stressful conditions or after extinction events, where sunlight is available, and grazing marine life is limited.
Challenging Landslide-Only Explanations for Wrinkled Textures
In deepwater environments, such textures are usually explained as marks left by underwater landslides that reshape sediment into ridges and grooves. Martindale was not convinced. The patterns she saw looked distinctly biological.
“It was one of those things, knowing what to look for and having that ‘search image’ of wrinkle structures in my head, that made me want to stop and dig into this,” she said.
In a study published in Geology, Martindale and her colleagues present a new explanation that links geological processes with biology. They argue that while a landslide did not directly create the wrinkles, it likely delivered nutrients to the seafloor, allowing microbes to grow.
New Theory: Landslides Enable Chemosynthetic Microbial Mats
The researchers propose that the wrinkles were formed by microbial mats that relied on nutrients carried to deep waters by the landslide instead of sunlight. This energy strategy, known as chemosynthesis, may also have allowed the microbes to release toxic sulfur compounds that discouraged other marine organisms.
Similar communities exist today in the deep ocean. For example, microbial mats often grow on whale carcasses that sink to the seafloor, creating nutrient-rich and short-lived “whale fall” ecosystems.
Deep-Ocean Microbes Reshape Understanding of Ancient Wrinkles
Jake Bailey, a professor at the University of Minnesota who studies how microbes influence Earth’s systems, said the findings challenge the idea that all ancient wrinkle structures come from a single type of microbial life.
“In the present, some of the largest microbial ecosystems on our planet are found in the dark ocean,” said Bailey, who was not involved with the research. “The research here shows that certain ancient sedimentary structures may record the presence of these chemolithotrophs rather than phototrophs (organisms that need sunlight to make energy). ”
New Fossil Insights and an Unexpected Scientific Journey
Martindale noted that the results suggest chemosynthetic microbial fossils may be more common than previously recognized. Interpreting wrinkle structures as purely physical features could lead scientists to overlook biological origins. This challenge is compounded by the lack of precise terminology for describing these textures.
“The terminology is pretty lax,” Martindale said. “Wrinkly can mean lots of things, so there’s a lack of diagnostic language.”
Martindale typically studies ancient coral reefs and mass extinctions, and she did not expect to shift her focus to deep-sea microbial mats. However, the discovery led her in a new direction.
“It’s really cool to have gone in this direction that I totally wasn’t expecting,” she said. “There was no hypothesis that I would find these microbial mats here. It was just being in the right place at the right time, with the right search image. And then being so stubborn as to not let go of it.”
Reference: “Chemosynthetic microbial communities formed wrinkle structures in ancient turbidites” by Rowan C. Martindale, Sinjini Sinha, Travis N. Stone, Tanner Fonville, Stéphane Bodin, François-Nicolas Krencker, Peter Girguis, Crispin T.S. Little and Lahcen Kabiri, 3 December 2025, Geology.
DOI: 10.1130/G53617.1
The research was funded by the National Science Foundation.
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