CAT-scans were taken of the recovered 96% of the 25.5 m core at 5 cm increments, revealing a series of ichnofabric "snapshots" spaced at <300 year intervals. Digital image analysis was used to quantify ellipticity and size trends in the bedding parallel ichnofabrics. Our model proposes that as porewater oxygenation increases, mean burrow orientations shift to become increasingly vertical. Alternately, as dissolved O (sub 2) levels decline, the habitable zone of oxygenation is compressed toward the sediment-water interface; organisms are restricted to less vertical burrow orientations on average, resulting in higher ellipticities in cross-section.