USE OF MULTISTRIPE LASER TRIANGULATION (MLT) TECHNOLOGY FOR QUANTITATIVE, THREE-DIMENSIONAL ANALYSES OF TRACE FOSSILS

We used a relatively new, low-cost multistripe laser triangulation (MLT) scanner and three-dimensional (3D) editing software for a range of semiquantitative and quantitative analyses of ichnofossils and modern traces. Our goal is to improve on existing ichnological techniques and apply newly developed analytical methods. We scanned and created 3D digital models of modern and fossil tracks, cocoons, burrows, and coprolites. We also captured digital models of burrow casts made by arthropods and vertebrates in soil-filled aquaria in a laboratory setting.

We created stereo pairs and anaglyph images from screen captures of digital models rotated precisely about vertical axes. Digital models were also rotated to create animations showing 360° views of traces. Software was used to produce cross-sectional views of trace fossils without requiring cutting of actual specimens. We used multiple cross sections at regular intervals to create contour maps of traces.

Quantitative methods we applied included measuring distances, angles, and calculating tortuosity indices. Two of the most useful properties measurable with MLT technology were surface area (SA) and volume; these have been used rarely in ichnology because they are difficult to measure with traditional methods. We used SA to calculate area exploited and developed a method for quantifying surface roughness. We measured volumes of scanned traces, and calculated a new measure termed volume exploited. We hypothesize that different tracemakers make burrows with characteristic volume to SA ratios; this is partially supported by statistical tests of previously published data. We also use volume to SA ratios to determine relative compactness—a metric adapted from building physics.

Data collected from digital models of trace fossils can be used to improve morphological and statistical analyses of trace fossils for ichnotaxonomic, paleopedological, paleobiological, paleoenvironmental, and paleohydrological interpretations. Burrow volumes from neoichnological experiments are especially useful because they can be used to calculate bioturbation rates in unit volume per unit time. Because the MLT scanner digitizes only the surface topography of objects, we found that this technology shows the most promise for exogenic traces and casts of endogenic traces.