Automated Precision Serial Grinding and Volumetric 3-D Reconstruction of Large Ichnological Specimens

To obtain deterministic three-dimensional reconstructions of large or complex trace fossils and to quantify the reconstructed models volumetrically, two stages are necessary: a laboratory stage, requiring precision serial grinding and high-resolution digital photography, and a computer analysis stage, where burrow volumes are visualized and analyzed. It is shown that the technique can be used successfully for bioturbated rocks that have little or no density contrast between the matrix and the burrows, upon which non-destructive techniques, such as CT scanning, are ineffective. To demonstrate the technique, several trace fossil samples (phycosiphoniform burrows, Nereites, Chondrites and Ophiomorpha) were reconstructed in 3 dimensions using the described serial grinding method. The method, employing automated, computer-controlled machinery followed by detailed computer analysis, enables volume calculations to be determined accurately for a single burrow, burrow networks and ichnofabrics.