Those faint lines, etched into a near-vertical face on Monte Cònero in central Italy, turned out to be much more than an oddity. New research argues they record a frantic rush of ancient marine reptiles, likely sea turtles, fleeing an earthquake-triggered underwater avalanche almost 80 million years ago.
Ancient drama on a modern climbing route
The story began when climbers at Cònero Regional Park noticed long, parallel furrows and arc-shaped marks in the pinkish Scaglia Rossa limestone. The patterns looked uncannily similar to trackways that had made headlines earlier that year from another site in the same park.
Those earlier grooves had been tentatively linked to a Cretaceous marine reptile pushing its paddles into soft seafloor mud. Recognising a possible repeat, the climbers contacted fellow climber and geologist Paolo Sandroni, who in turn reached out to Alessandro Montanari, director of the Coldigioco Geological Observatory.
What looked to climbers like odd, weathered ruts may instead be frozen moments from a chaotic underwater escape 79 million years ago.
Sandroni returned to the cliff with another team member, scaling the wall again, this time not for sport but for science. They documented the surface with detailed photographs and a drone survey and collected rock samples from just above the track-bearing layer.
A seabed turned mountain, and a mystery locked inside
Today, Monte Cònero is a scenic headland overlooking the Adriatic. During the Late Cretaceous, the same area lay hundreds of metres underwater, part of a deep-sea basin slowly filling with fine mud and microscopic shells.
Over tens of millions of years, tectonic forces folded and uplifted these sediments, turning ancient seafloor into a mountain. The Scaglia Rossa limestone that now forms cliffs and climbing routes once formed a calm, muddy seabed.
Analysis of the samples collected above the tracks points to a specific moment in that long history. The rock shows signs of a massive underwater slide of mud and sediment, known as a submarine mass-transport deposit. The team links this to strong seismic activity in the region during the Late Cretaceous.
Evidence in the rock suggests an earthquake shook the ancient seabed, triggering an underwater avalanche that both panicked the animals and preserved their tracks.
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Thin sections of the limestone, examined under a microscope, contain microfossils of organisms that usually live on or near the seafloor. Their presence supports the idea of a relatively deep, quiet marine environment before the sudden disturbance.
Was it really a sea turtle stampede?
The trackways consist of repeated grooves and depressions that look like strokes from strong forelimbs pushing against soft sediment. Hundreds of these marks appear on a single bedding surface, all preserved within the same layer.
During the Late Cretaceous, the only vertebrates large enough to carve such tracks into the seabed were marine reptiles: sea turtles, plesiosaurs and mosasaurs. Plesiosaurs and mosasaurs are generally thought to have been more solitary animals. Sea turtles, by contrast, can congregate in large numbers for feeding or nesting.
Researchers speculate that, as in some coastal areas today, multiple turtles may have gathered near a Cretaceous shoreline to forage or lay eggs. When the seabed began to shake, these animals reacted fast.
- Some likely pushed off the seafloor and headed upward into the water column.
- Others may have scrambled along the bottom toward deeper, presumably safer, water.
- The sudden downslope movement of sediment – an underwater avalanche – then swept across the area.
Because that slurry of mud buried the seafloor almost immediately, the tracks escaped the usual fate of being churned up by worms, clams and other burrowing creatures. Under normal conditions, benthic animals “garden” the seabed, erasing tracks within days or weeks.
Not everyone agrees on the track maker
While the geological setting points strongly to a seismic event and rapid burial, the exact identity of the track makers remains debated.
Michael Benton, a vertebrate palaeontologist at the University of Bristol who was not involved in the study, has raised questions about the interpretation. He notes that the pattern of the tracks appears unusual for typical swimming motions.
The grooves suggest both forelimbs driving into the sediment together, a kind of underwater “punting” that doesn’t neatly match modern turtle swimming.
Modern sea turtles usually move with a more fluid, “underwater flying” motion, their front paddles tracing a figure-eight rather than pushing down in unison. Benton also points out that many marine vertebrates would simply leave the seafloor and swim away from danger rather than moving along the bottom.
Montanari and colleagues acknowledge that further work is needed to pin down the track maker. What they argue with more confidence is the sequence of events: a calm deep seafloor, a sudden earthquake, frightened animals moving in haste, and an avalanche that quickly sealed the surface.
Reading earthquakes in stone and footprints
The Cònero site adds to a growing set of cases where ancient earthquakes have left not only shattered rocks and slumped sediments, but behavioural traces of animals that lived through the shaking.
Submarine landslides linked to “megaquakes” have been documented elsewhere, such as along the Cascadia subduction zone off North America. In those settings, scientists infer seismic events mainly from disrupted layers and deep-sea deposits. At Monte Cònero, the potential turtle tracks provide a more direct, almost cinematic glimpse of how animals responded.
| Clue in the rock | What it suggests |
|---|---|
| Parallel grooves in limestone | Repeated limb strokes by large marine reptiles |
| Massive, chaotic mud layer above tracks | Submarine avalanche triggered shortly after track formation |
| Deep-sea microfossils | Seafloor hundreds of metres below the surface |
| Known seismic activity in the formation | Likely earthquake causing shaking and slope failure |
How seafloor tracks manage to survive for 79 million years
Preserving any footprint is tricky. Preserving footprints on the deep seabed is especially rare. Currents, chemical changes and burrowing organisms constantly rework marine sediments.
For a trackway to last long enough to turn into rock, several conditions need to line up:
- The sediment must be soft enough to hold an impression, but cohesive enough not to collapse immediately.
- The animal needs to move across the surface during that brief window.
- A rapid blanket of new sediment has to arrive soon after, sealing the tracks away.
In the Cònero case, the earthquake likely shook unstable mud on a submarine slope. The same disturbance that frightened the turtles (or other reptiles) also sent a slurry of sediment rushing downslope. As that avalanche spread out and settled, it entombed the still-fresh impressions.
What an ancient “stampede” tells us about modern seas
Although the scene played out in the Late Cretaceous, the processes involved are still active on today’s seafloor. Strong earthquakes continue to trigger submarine landslides that can damage cables, alter habitats and even generate tsunamis.
Modern turtles and other marine animals also respond to seismic events and sudden slope failures, though direct observations are rare. Sites like Monte Cònero offer a long-term record of how life has coped with violent geological episodes through deep time.
The idea of a “stampede” under water might sound strange, yet it captures a useful concept: multiple individuals reacting at once to a sudden threat, leaving a dense cluster of overlapping tracks. Even if future work shows a mixture of reptiles rather than only turtles, the site still records a collective, rapid response to environmental stress.
Key terms behind the headlines
Two technical ideas sit at the heart of this story: the Late Cretaceous and submarine avalanches.
The Late Cretaceous was the final stretch of the age of dinosaurs, running from about 100 to 66 million years ago. Sea levels were high, climates were generally warm, and many modern groups of marine animals were already established. Large sea turtles, early relatives of modern forms, swam alongside mosasaurs and plesiosaurs.
A submarine avalanche, or mass-transport deposit, is a large downslope movement of sediment under water. These events can be triggered by earthquakes, rapid sediment loading, gas release or slope oversteepening. They can reshape seafloor landscapes in minutes, carving channels and burying ecosystems under metres of mud.
Imagining the moment
Picture a quiet Late Cretaceous seabed, hundreds of metres down. Fine mud drifts down like underwater snow. A group of large turtles forages, their bodies half-buoyant but still pressing against the soft bottom as they move.
Then the seafloor trembles. A distant fault slips. Sediment on a slope nearby begins to fail. The turtles push hard against the mud, either launching themselves upward or racing along the bottom downslope or away from it. Their strokes gouge deep grooves.
Within minutes, a dense, muddy flow surges through, blanketing the area. The grooves vanish from view but not from history. Only when tectonic forces lift and tilt the basin, and humans start climbing the new cliffs, do those frantic moments reappear in daylight.
For climbers at Monte Cònero today, the story adds a new dimension to a familiar route. Every time a hand or foothold seeks purchase on the limestone, it rests on former seafloor that once shook, slid and briefly hosted what may have been a turtle stampede in the dark of an ancient sea.
