Lidar used to track dinosaur prints in Arkansas quarry
Image credit: Russell Cothren
Scientists using laser-imaging technology have documented and digitally preserved the first known set of theropod dinosaur tracks in the state of Arkansas.
The tracks, first discovered in 2011 in a working gypsum quarry near Nashville, Arkansas, have since been destroyed by the commercial activity taking place in the quarry.
However, high-resolution digital scans captured over a two-week period in 2011 allowed a team of researchers to study the tracks and determine that they were made by Acrocanthosaurus, a large, carnivorous dinosaur. The findings extended the known range of Acrocanthosaurus 56 miles east to the western shore of an ancient inland sea.
“It actually confirms that the main genus of large theropods in North America was Acrocanthosaurus,” said Celina Suarez, an assistant professor in the Department of Geosciences who was part of the team that documented and studied the tracks. “It now has been found in Wyoming, Utah, Oklahoma, Arkansas and Maryland, a huge range.”
After the tracks were discovered, researchers received a $10,000 Rapid Grant from the National Science Foundation to document the site quickly. The University of Arkansas’ vice provost for research and economic development and the J William Fulbright College of Arts and Sciences provided matching grants, for a total of $30,000.
The mining company moved its operations to give the researchers a short window of time in which to document the find. Researchers mounted the lidar equipment on a lift to document the site, soon to be lost.
The team used lidar - which stands for light detection and ranging - because traditional methods would have taken too long. “From a technical standpoint, it’s important that the ability to rapidly scan such a large area is available to palaeontologists,” Suarez said. “It was invaluable for this project since we had such little time to work.”
The researchers also created a detailed, publicly accessible online map of the site and the tracks. Brian Platt, an assistant professor of geology from the University of Mississippi, led the study. Researchers from the University of Arkansas Center for Advanced Spatial Technology (Cast) provided the scanning equipment and expertise.
The site had two different-sized Acrocanthosaurus tracks, suggesting both adult and younger animals walked the ancient tidal flat about 100 million years ago during the Cretaceous Period. It also contained tracks made by sauropods - long-necked, plant-eating dinosaurs.
Lidar uses a pulsed laser to measure distances to the earth in tiny increments, generating a data ‘point cloud’ that is used to digitally recreate a physical space. In this case, the equipment was mounted on a lift over the site. By analysing carbon and oxygen isotopes of the rock at the track surface, researchers determined that the track surface was indeed the surface that the animals stepped on, rather than an underlying layer that remained when the original surface eroded.
The digital reconstruction of the dinosaur trackway site can be viewed at the Cast web site.
The team’s experiences were reported in scientific journal Plos One.
Archaeologists are increasingly able to use advanced radar and sonar techniques to find and document ancient sites. For example, British archaeologists created a map of a medieval settlement at the Old Sarum archaeological site near Salisbury, Wiltshire, using magnetometry, ground-penetrating radar and electric resistive scanning techniques - all without having to dig into the ground.