A new study from McGill University is reshaping how scientists date dinosaur fossils in Alberta's Dinosaur Provincial Park (DPP). Using advanced drone-assisted 3D mapping, researchers have uncovered significant variations in a key geological marker, challenging long-standing methods of determining the ages of dinosaur fossils.
The researchers say their findings, published in Palaeontologia Electronica, could lead to more accurate reconstructions of ancient ecosystems, helping us better understand Earth's history and how past biodiversity changes inform present and future life.
"We've essentially shown that the dating method used for decades in Dinosaur Provincial Park may not be as reliable as previously thought," said Alexandre Demers-Potvin, a postdoctoral researcher who led the study as a PhD candidate at McGill's Redpath Museum.
Dinosaur Provincial Park is a UNESCO World Heritage Site since it preserves an unparalleled dinosaur fossil record from the Late Cretaceous period. For decades, paleontologists have relied on a distinct rock boundary - the contact between the Oldman and Dinosaur Park Formations - as a reference point to estimate the ages of fossil quarries in the park. To do this, they compare how high or low a fossil site is relative to that boundary. However, this method only gives a rough age estimate rather than a precise date, unlike absolute dating methods, which use radioactive elements in rocks to determine exact ages.
The new study reveals that this boundary fluctuates in elevation by as much as 12 metres over short distances, introducing a level of uncertainty that could alter interpretations of when different species lived.
"If the reference point itself varies significantly, then our estimates of individual fossil ages could be off by a considerable margin," said Demers-Potvin.
Building a more accurate timeline
To address these uncertainties, Demers-Potvin and co-author Professor Hans Larsson used drones to capture around a thousand high-resolution images of a key fossil site in the park. These images were processed through a technique called structure-from-motion photogrammetry, which allowed the team to construct a precise 3D model of the terrain which is geolocated with GPS coordinates measured in the field.
The results showed that it might be possible to estimate fossil ages by identifying their source sedimentary layers and tracing those over long distances wherever possible. The researchers say this dating method might be more dependable than referring to the boundary between the Oldman and Dinosaur Park Formations, since it would not require elevation measurements which are now shown to rise and fall by several metres in different areas of the park.
"This opens the door to a more refined approach for understanding how different dinosaur species succeeded one another over time," said Demers-Potvin. "By mapping these sedimentary layers over a broader area, we could develop a much clearer picture of biodiversity shifts in an ancient terrestrial ecosystem."
About the study
High local variability in elevation of the Oldman-Dinosaur Park Formation contact revealed by digital outcrop reconstruction, and implications for dinosaur biostratigraphy of the Late Cretaceous (Campanian) Belly River Group of Alberta, Canada by Alexandre V. Demers-Potvin and Hans C.E. Larsson was published in Palaeontologia Electronica
