A CHRONOSTRATIGRAPHIC FRAMEWORK FOR THE RISE OF THE EDIACARAN MACROBIOTA: NEW CONSTRAINTS FROM MISTAKEN POINT ECOLOGICAL RESERVE, NEWFOUNDLAND (Invited Presentation)

The Conception and St. John’s Groups of southeastern Newfoundland contain some of the oldest known fossils of the Ediacaran macrobiota. Mistaken Point Ecological Reserve (MPER) UNESCO World Heritage Site is an internationally recognised locality for such fossils, and hosts early evidence for both total-group metazoan body fossils, and metazoan-style locomotion. The MPER sedimentary succession includes ~1500m of fossil-bearing strata containing numerous dateable volcanogenic horizons, and therefore offers a crucial window into the rise and diversification of early animals. Here we present six stratigraphically-coherent radio-isotopic ages derived from zircons from volcanic tuffites of the Conception and St. John’s Groups at MPER. We use our new ages to construct an age-depth model for the sedimentary succession, constrain sedimentary accumulation rates, and convert stratigraphic fossil ranges into the time domain to facilitate integration with time calibrated data from other successions. Combining this age model with compiled stratigraphic ranges for all named macrofossils within the MPER succession, spanning 76 discrete fossil-bearing horizons, enables recognition and interrogation of potential evolutionary signals. Peak taxonomic diversity is recognised within the Mistaken Point and Trepassey Formations, and uniterminal rangeomorphs with undisplayed branching architecture appear several million years before multiterminal, displayed forms. Together, our combined stratigraphic, palaeontological, and geochronological approach offers a holistic time-calibrated record of evolution during the mid-late Ediacaran Period, and a framework within which to consider other geochemical, environmental, and evolutionary datasets.