The Lava That Became a Fossil Quarry: Queensland's Cretaceous Dinosaur Trackways

Near the town of Winton, in central Queensland, the ground is stamped with the footsteps of animals that died 95 million years ago. Thousands of dinosaur tracks lie exposed across the Lark Quarry Conservation Park—a single slab of stone that holds the world's largest known concentration of dinosaur footprints. The rock that preserved them was not sandstone or mudstone, but volcanic ash.

The Ash That Fell on a Floodplain

In the mid-Cretaceous, around 95 million years ago, eastern Australia sat much closer to the South Pole than it does today. The continent was still attached to Antarctica and South America, and the climate was cool and wet. Central Queensland was a broad floodplain crossed by meandering rivers, dotted with conifers and ferns.

To the east, a chain of active volcanoes ran along the edge of the continent, similar to the modern Andes. These volcanoes erupted frequently, and huge clouds of fine volcanic ash drifted westward, settling onto the floodplains like snow. Each eruption deposited a thin layer of ash that mixed with the mud and sand of the river flats.

When dinosaurs walked across these wet ash-laden sediments, their feet sank deep, leaving impressions that filled with fresh ash and silt. Over time, layer upon layer of ash and sediment buried the footprints, sealing them from erosion. The ash itself acted as a preservative, smothering microbial activity and preventing scavengers from disturbing the tracks.

A Stampede Preserved in Stone

The most famous site, Lark Quarry, preserves a single extraordinary event. In 1977, a shearer named Glen Seymour noticed curious depressions on a rocky outcrop. When palaeontologists excavated the site, they found more than 3,300 individual footprints covering 250 square metres.

The tracks tell a story. A herd of small, two-legged omnivorous dinosaurs—likely Muttaburrasaurus or a similar ornithopod—was walking across the floodplain when something spooked them. The footprints shift from walking to running, the spacing between tracks widening as the animals broke into a sprint. Among their prints are the larger three-toed tracks of a theropod predator, possibly a relative of Australovenator, moving in pursuit.

One footprint shows the impression of a dinosaur slipping in the mud, its claw marks dragging sideways as it regained its footing.

The entire scene was buried within hours or days by a fresh ashfall, freezing a moment of Cretaceous panic into stone.

Reading the Rock Record

The volcanic ash did more than preserve footprints. It also carried chemical signatures that help geologists date the site precisely. The ash contains crystals of zircon, which can be radiometrically dated to 95 million years, placing the tracks in the Cenomanian stage of the Cretaceous.

The ash chemistry also reveals the composition of the parent magma. The Winton area ash deposits are rich in silica, typical of explosive rhyolitic eruptions from subduction zone volcanoes—the same volcanic system that created the Whitsunday Islands and the Great Dividing Range's volcanic roots.

Not all ash beds are the same. Some layers are coarse and gritty, deposited close to the volcanic vent. Others are fine as talcum powder, carried hundreds of kilometres by high-altitude winds. By mapping the thickness and grain size of ash layers across Queensland, geologists have traced the location of Cretaceous volcanoes that have since eroded away.

What the Footprints Reveal

The Lark Quarry tracks have reshaped our understanding of dinosaur behaviour. The running speeds have been calculated from stride length: the smaller dinosaurs moved at around 12 kilometres per hour, a brisk jog. The theropod was slower, around 8 kilometres per hour, suggesting it was stalking rather than sprinting.

The tracks also reveal social behaviour. The herd of ornithopods moved as a group, with smaller individuals at the edges and larger ones in the centre—a pattern seen in modern herd animals. This is some of the earliest evidence of complex social structure in dinosaurs.

Not all the tracks at Lark Quarry are from running animals. Some show dinosaurs standing still, their feet sinking deep into the mud as they paused. One set of tracks shows a dinosaur lying down, its body resting on the sediment, then standing up and walking away—the only known example of a resting dinosaur footprint in Australia.

The Living Record

The volcanic ash that fell on that Cretaceous floodplain has long since weathered to clay, but the footprints remain. Each year, rain and wind slowly erode the surface, revealing new tracks that were previously hidden. The site is now protected as a conservation park, and a building covers the main trackway to slow the weathering.

Across Queensland, similar ash deposits hold more tracks still buried. The volcanic eruptions that once terrified the dinosaurs are long silent, but the ash they left behind continues to speak—not of destruction, but of the ordinary moments of ancient lives: a herd crossing a floodplain, a predator following, and a slip in the mud that left a mark for 95 million years.