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Center for Advanced Spatial Technologies

University of Arkansas

Salvaging a Newly Discovered Dinosaur Trackway from Southwest Arkansas

Home » Research » Archaeology/Historic Preservation » Archaeological Geomatics » Archaeological Laser Scanning » Documenting Dinosaur Trackways using LiDAR

Explore the data on your own at http://trackways.cast.uark.edu

In June 2011, a new dinosaur trackway site was exposed on private property in southwest Arkansas. Among the numerous sauropod tracks and trackways was the first reported occurrence of theropod trackways in The Natural State.

The dinosaur trackways were exposed over an area of approximately 6000 m² on a thin (ca. 0.5 - 0.7 m thick) limestone layer within the De Queen Limestone member of the Trinity Group (early Cretaceous Periods, approximately 120 - 115 million years old).

A salvage survey of the site acquired high-resolution (0.006 m resolution) LiDAR of the entire exposed trackway limestone, very high resolution LiDAR (0.001 m resolution) of selected theropod tracks, a photo mosaic of ca. 1700 m2 (1-m2 photo grid) of the limestone surface exposing the greatest concentration of tracks, 36 plaster casts of individual theropod tracks (possibly representing two different theropod types), several thousand oblique photos of tracks and trackways, high-definition professional video, and rock samples of sedimentary strata above, below, and within the trackway limestone for isotopic and paleoenvironmental analysis.

The Z+F Imager 5006i, a phase-based scanner that emits a constant beam of laser light, was mounted on the boom lift and was used to sweep across the landscape to measure and record up to 500,000 points per second (shown in image above).

The Leica ScanStation C10 was used to record an overview of the site from a ridge above the site. This time-of-flight scanner incorporates discrete pulses of laser light at a rate of 50,000 per second, each recording a point in space. Depending on the path of a given laser pulse, up to four return pulses are recorded by the instrument's receiver. The location where each LiDAR return pulse originated is computed, allowing the researchers to study a three-dimensional “point cloud” representing the tracks.

The largest theropod tracks (apparent foot length ca. 0.7 m long and apparent foot width ca. 0.6 m wide) occur in two 30-m long trackways that are parallel but opposing directions. Individual tracks along each trackway show significant inward rotation with left and right pes (hind foot) impressions nearly in-line. Several other theropod trackways in excess of 100 m are also present. Individual tracks within these longer trackways are somewhat smaller (approximately half the size of the largest theropod tracks), show less inward rotation, and display greater interpedal distance with distinct claw, digit and foot pad impressions. These tracks may represent a different theropod species than the largest tracks. The trackways and exposure surface have important implications for early Cretaceous paleogeography and paleoclimate, theropod biomechanics and biogeography.

This web site (http://trackways.cast.uark.edu) presents an interactive visualization of the main portion of the trackway site (approximately 4200 m2) derived from the high-resolution LiDAR data. Viewers can zoom and pan to investigate tracks and trackways. The apparent illumination and shading can be altered using the check boxes in the legend to better highlight tracks and trackways; depending on their orientation, visibility of tracks and trackways can be enhanced by changing the apparent azimuth of illumination.

Research on trackways and development of this experimental web site were supported by a grant from the National Science Foundation, Award No. 1143968 with additional support from the University of Arkansas Fulbright College of Arts & Sciences and University of Arkansas Office of Research and Economic Development. LIDAR data acquisition, processing, and production of the web site were completed by the University of Arkansas Center for Advanced Spatial Technologies (CAST). Site research was led and managed by the University of Arkansas Department of Geosciences.