QUANTITATIVE VARIABILITY of BURROW PERCENTAGE ESTIMATED from 2D VIEWS: EXAMPLE from THALASSINOIDES-BEARING STRATA, CENTRAL SAUDI ARABIA

This study examines computed tomography (CT) scans of a 15.24-cm diameter and 17.1-cm length core cut from Thalassinoides-bearing strata (Hanifa Formation, central Saudi Arabia) to explore the quantitative variability in burrow percentage when estimated using 2D views. A cropped quadrangular prism of this core allowed 202 2D slices in two vertical orientations and 165 horizontal 2D slices. Thalassinoides volume represents 20.0% (burrow percentage) of the total volume within this cropped quadrangular prism. The estimated burrow percentage by the 2D vertical slices varies from 11.8% to 30.3% with a mean value of 19.9% 6 3.3% and 19.6% 6 3.9%, and coefficients of variation of 17% and 20%, for the two vertical orientations. A wider range and slightly more variability are found when estimated burrow percentage using the horizontal slices (burrow percentage range from 6.1% to 33.1% with a mean value of 19.8% 6 6.5% and coefficient of variation of 33.1%). However, analysis of variance results indicated no statistically significant difference between the distribution of the burrow percentage among vertical and horizontal slices. A test of how randomly selected slices of the CT scan would represent the burrow percentage indicated that even five randomly selected slices could retain a mean comparable to the actual burrow percentage of the CT scan. Based on these results, we suggested a statistical way to quantify the uncertainty associated with estimating the burrow percentage from 2D views, an important step toward a complete understanding of variability in burrow percentage (and bioturbation intensity) when estimated from 2D views.