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Trenches that could be evidence of a sea turtle stampede have been found on a cliff in Italy by rock climbers. . | Credit: Paolo Sandroni
Mountaineers in Italy have stumbled upon evidence of what appears to be a sea turtle exodus that occurred nearly 80 million years ago. Now, new research suggests these ancient marine reptiles were fleeing an earthquake.
The climbers recognized the significance of their discovery because the trenches in the rock on Monte Conero, overlooking the Adriatic Sea, reminded them of others that had headlines earlier that year. These burrows were found in another part of the same regional park and were attributed to a Cretaceous marine reptile that pressed its paddles into the seabed. They consulted with a fellow mountaineer and geologist, Paolo Sandroni, whom he contacted Alessandro Montanaridirector of the Coldigioco Geological Observatory (OGC).
After investigating what these grooves might be, the researchers revealed their findings in a study published Nov. 19 in the journal. Cretaceous research.
Sandroni and another team member climbed back into the area to collect rock samples and document the site using a drone.
Hundreds of these tracks are located on a layer of Scaglia Rossa limestone in the Cônero Regional Park, a formation that has been studied extensively for decades and preserves millions of years of deep sedimentation, study co-author Montanari told Live Science.
What is now part of a mountain was once a deep bedrock folded and pushed up by tectonic forces millions of years ago, he said. Rock samples collected immediately above the tracks and analyzed by the team reveal important clues about the location of the tracks and the story behind them. For example, they suggest that sea turtles lived about 79 million years ago during the Late Cretaceous period and indicate that the limestone was part of an underwater mudslide triggered by a earthquake.
Abundant seismic activity in this formation is also supported by decades by collective study. Thin slide sections of rock samples reveal microfossils of organisms living along the sea floor, suggesting a seafloor environment hundreds of meters deep.
Researchers say the trenches appear to be the result of turtles fleeing an earthquake that triggered an underwater avalanche. | Credit: Paolo Sandroni
Normally, any traces left by the animals would be washed away by currents on the sea floor and “worms, shells and [other] benthic organisms,” Montanari said. “Practically the seabed garden,” he noted. But an earthquake caused an underwater avalanche within minutes of making the tracks, preserving them, he said.
The only vertebrates large enough to make these tracks in the Late Cretaceous were marine reptiles such as sea turtles, plesiosaurs, and mosasaurs. The latter two are thought to have been mostly solitary, but if ancient sea turtle behavior mirrored that of some of today’s species, the researchers said, then they may have foraged near shore or left the water to lay their eggs. Whatever brought them together, an earthquake sent them all fleeing at once, the team in the study suggested, forcing some of the turtles to swim in the water above toward the open sea and others away. closer to the deeper sea floor. The impending underwater avalanche pushed them further out of the way.
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Michael Bentonprofessor of vertebrate paleontology at the University of Bristol in Britain, who was not involved in the research, said the study clearly shows the geological context, but questioned which animal made the tracks.
“The tracks are unusual because they appear to show underwater pathways where the two forelimbs enter the sediment together and the animal pushes forward,” he told Live Science. Most vertebrates tend to “limb or swim with their limbs out of sequence,” rather than putting two limbs down at the same time, he said. “Sea turtles generally have a very efficient way of swimming,” he said, “a bit like underwater flight, where the front flippers rotate” similar to a figure-eight pattern that doesn’t seem to match the tracks found. He also wonders why he wouldn’t just “leave the bottom of the sea and swim”.
Montanari said that while the footprints would benefit from further research, it is clear from a geological point of view that there was an underwater avalanche triggered by an earthquake. He said he hopes their work will prompt fossil experts to study the site further.