While exploring ancient seabeds in Morocco's Dadès Valley, researchers discovered wrinkle structures in deep-water sediments that suggest chemosynthetic microbes thrived there 180 million years ago. These formations, typically linked to shallow, sunlit environments, appeared in rocks formed far below the ocean's surface. The find challenges assumptions about where and how early life signatures are preserved.
Dr. Rowan Martindale, a paleoecologist and geobiologist at the University of Texas at Austin, noticed the unusual wrinkle structures during a hike through the Dadès Valley in Morocco's Central High Atlas Mountains. She was part of a team, including Stéphane Bodin from Aarhus University, studying the ecology of ancient reef systems that existed when the area was underwater. The group had to cross layers of turbidites—sediments deposited by dense underwater debris flows—to reach the reefs.
"As we're walking up these turbidites, I'm looking around and this beautifully rippled bedding plane caught my eye," Martindale recalled. "I said, 'Stéphane, you need to get back here. These are wrinkle structures!'"
Wrinkle structures consist of tiny ridges and pits, millimeters to centimeters in size, formed by microbial mats on seafloors. They are usually created by photosynthetic algae in shallow, sunlit tidal zones and are rarely preserved in rocks younger than 540 million years old, as animal activity tends to disturb them. The discovered structures, however, lay in 180-million-year-old turbidites deposited at depths of at least 180 meters, beyond sunlight's reach and during a period of widespread seafloor disturbance by animals.
To verify the find, the team examined the rock layers and conducted chemical tests, revealing elevated carbon levels beneath the wrinkles that indicate a biological origin. Comparisons with modern deep-sea footage showed chemosynthetic bacteria—powered by chemical reactions rather than light—forming similar mats in dark ocean environments.
Turbidite flows likely supplied nutrients and reduced oxygen, fostering these bacteria during calm intervals between flows. Occasionally, the mats were buried and preserved before the next flow could erase them.
"Let's go through every single piece of evidence that we can find to be sure that these are wrinkle structures in turbidites," Martindale said, noting their unexpected presence in deep water.
The discovery, detailed in the journal Geology, prompts a reevaluation of wrinkle structures as potential evidence of ancient microbial life in overlooked deep-sea settings. "Wrinkle structures are really important pieces of evidence in the early evolution of life," Martindale explained. "By ignoring their possible presence in turbidites, we might be missing out on a key piece of history of microbial life."