Sometimes big discoveries begin with a moment of surprise. For Dr. Rowan Martindale, a paleoecologist and geobiologist at the University of Texas at Austin, that moment came during a walk through Morocco’s Dadès Valley in the Central High Atlas Mountains.
As she crossed layers of ancient rock, something unusual on the ground made her stop in her tracks.
Martindale and her colleagues, including Stéphane Bodin from Aarhus University, were studying ancient reef systems that once lay beneath the ocean.
To reach those reefs, they had to walk across thick layers of rock known as turbidites—sediments formed when underwater landslides sent clouds of mud and debris cascading down the seafloor. These deposits often show ripple marks, shaped by flowing water.
But Martindale noticed something else layered on top of the ripples: delicate, wrinkled textures that didn’t seem to belong there.
These features, known as wrinkle structures, are tiny ridges and pits that usually form when microbial or algal mats grow across sandy surfaces.
Today, such structures are typically found in shallow coastal areas where sunlight allows algae to thrive.
They are also rare in rocks younger than about 540 million years, because animals began burrowing through sediments and destroying these fragile textures around that time.
The rocks in Morocco posed two big problems. First, they were deposited deep underwater—at least 180 meters below the surface—far beyond the reach of sunlight.
Second, they were only about 180 million years old, a time when animals were already widespread and actively disturbing the seafloor.
By all conventional understanding, wrinkle structures should not have survived, or even formed, in this setting.
Rather than dismissing the odd textures, Martindale decided to investigate carefully. The team confirmed that the rocks were indeed turbidites, ruling out the possibility that the sediments formed in shallow water.
Next, they tested whether the wrinkles truly had a biological origin. Chemical analysis showed higher levels of carbon just beneath the wrinkled layers, a strong hint of past biological activity.
To explain how life could form these structures without sunlight, the researchers turned to modern deep-sea observations.
Videos from remotely operated vehicles have shown that microbial mats can grow on today’s deep seafloor using chemosynthesis—drawing energy from chemical reactions rather than sunlight. These bacteria thrive in low-oxygen environments rich in nutrients.
The team concluded that ancient turbidites likely carried organic material and nutrients downslope, creating conditions ideal for chemosynthetic microbes. During quiet periods between debris flows, these microbes formed mats on the seafloor. Over time, the mats developed wrinkled textures.
Most were later destroyed by new sediment flows, but occasionally they were preserved, leaving behind the rare structures seen in Morocco.
The findings, published in the journal Geology, suggest that scientists may have been overlooking important signs of ancient life. Wrinkle structures have long been seen as evidence of photosynthetic organisms in shallow water. This study shows they can also form deep in the ocean, expanding where researchers might search for traces of early microbial life.
By broadening this perspective, Martindale hopes geologists will revisit environments once considered unlikely to preserve signs of life—and uncover more hidden chapters in Earth’s biological history.
Source: KSR.
