THE TEMPORAL SIGNIFICANCE OF EQUILIBRICHNIA WITHIN THE BALDONNEL FORMATION, NORTHEAST BRITISH COLUMBIA

A detailed outcrop study of the Baldonnel Formation in northeastern British Columbia reveals a remarkable trace fossil assemblage. The trace fossil suite includes excellent examples of equilibrichnia that formed as a result of organisms vertically adjusting to aggradation or degradation of the sediment surface. Common equilibrichnia observed within the succession include Diplocraterion, Teichichnus. and bivalve adjusting traces. These ichnofossils lend insight into the temporal nature of the depositional environment (a seasonally storm-dominated shoreface). Detailed observations of the nature of burrow spreiten, the inferred direction of animal movement in the substrate, and the magnitude of animal adjustments in the sediment, can be related to the magnitude of storm erosion, and ensuing sediment deposition. Post-storm colonization patterns and the persistence of robust (2-3 yr old?) bivalves support the interpretation of deposition within a storm-dominated environment. Traces that persist upwards through amalgamated bedsets represent colonization of, and equilibration through, sediment that was deposited during a single storm event. Where ichnologic data are absent or ignored, however, one may interpret the amalgamated bedsets as representing multiple storm deposits. This analysis of equilibrichnia within shoreface deposits demonstrates further applications of ichnology in the reconstruction of temporal sedimentary events.