Multi-storm events recorded on Panopea burrows (Pliocene, Spain): The importance of sequestered information inside burrows

The fossil record is essentially characterized by time-averaged assemblages as a consequence of the mixture of multiple generations of organisms into a single stratigraphic horizon. In order to investigate this issue a quantitative taphonomic analysis of fossil assemblages filling up Panopea burrows (ichnogenus Scalichnus) and those preserved in sediment without this trace fossil on of a Pliocene deposit of SW Spain were carried out. A combination of processes can be inferred from the analysis of the fossils infilling Scalichnus burrows. Passive concentration of shells within trace fossils were is interpreted to have been produced during event processes (most likely storm events) and active burrowing of bivalve trace-makers probably represented the background conditions. These shell concentrations inside Scalichnus burrows constitute a potential sedimentological implement to understand the multi-storm events recorded on the taphonomic signature of the biofabric that otherwise may be unnoticed. The studied examples can be used as proxies for sequencing a series of amalgamated storm events inside bivalve burrows, assessing the magnitude and frequency of erosional events, and analysing the positive taphonomic effect of these equilibrium trace fossils.