Quantifying Bioturbation in Ediacaran and Cambrian Rocks

Trace fossils, which record the activities of benthic metazoans, ­typically are bedding-parallel and are preserved along bedding planes in Ediacaran-Cambrian siliciclastic rocks. The quantity of bioturbation present within a bed can reflect a variety of ecological and environmental factors, including oxygenation, salinity, sediment accumulation rate, substrate consistency, and benthic community ­structure. Thus, quantitative data can augment qualitative descriptions of early bioturbation, in turn facilitating the detailed characterization of facies and the meaningful comparison of Ediacaran-Cambrian sedimentary data. In this chapter, we review and describe a number of new and established methods for estimating quantities of bioturbation, both from bedding plane surfaces and from vertical outcrops or core sections. These methods are designed to complement descriptive paleontological, ichnological, and sedimentological data-collection procedures, and many could be incorporated into a variety of early-life studies.