Ichnofabric index

The Droser-Bottjer ichnofabric index is a method used to quantify the degree of bioturbation in a sedimentary rock. It involves grading the amount of trace fossil activity on a scale of 1–6; a value of 1 indicates that bioturbation is entirely absent, whereas the highest grade would involve a bedding plane containing over 60% trace fossil cover.^[1]

Trace fossils occupy a large proportion of this bedding plane.

Application

Ichnofabric index can be applied in either a vertical or horizontal aspect. The vertical component provides an indication of the interplay between physical and chemical aspects of the environment and the degree of biological activity.^[2] The vertical ichnofossil index is harder to measure; it involves quantifying the amount of disturbance to the original sedimentary fabric.^[3]