Bioturbation in deep-sea fine-grained sediments: influence of sediment texture, turbidite frequency and rates of environmental change

Summary In the deep sea, burrowing infauna can adapt to variation in sediment texture within < 100–300 years. When there is continuous sedimentation, a continuous bioturbation process also takes place and the biogenic trace association found in the fossil record may be dominated by deeply penetrating burrows. A low-diversity trace fossil association (Zoophycos ichnofacies) is typical. On the other hand, when turbidites interrupt the continuous bioturbation process, a highly diverse trace fossil association is often found in the fossil state that also contains highly organized near-surface traces (Nereites ichnofacies). This biotope is usually controlled by the non-turbiditic sedimentation rate and the recurrence time of turbidites. Biogenic trace assemblages are mainly controlled by the nature of sedimentation and other environmental conditions rather than by water depth. Therefore, the widely accepted use of trace fossils as palaeobathymetric indicators in the deep sea may be restricted.