MindTheGap · Quantifying the completeness of the stratigraphic record and its role in reconstructing the tempo and mode of evolution

Darwin identified the incompleteness of the geological record as a major concern in our ability to reconstruct the evolutionary history from fossils. Geological strata are not, however, a random selection of the past, but are deposited and preserved in processes which can be modelled mathematically. This project employs numerical forward modelling, a technique from sedimentary basin analysis, to quantify how stratigraphic gaps affect evolutionary patterns in the fossil record. It focuses on tropical carbonate platforms, because they are the richest archive of biodiversity through the Phanerozoic and are directly formed by organisms, thus preserving a positive feedback loop between the environment, evolution, and sediment formation. Completeness of the record depends on the time scale of measurement. Previous work demonstrated that long gaps in the record, in the range of 106-107 years, are reflected in biodiversity reconstructions. Here we address shorter gaps (103-105 years), which are more frequent, but harder to detect. They can be predicted using models of stochastic sedimentation, astronomical forcing, and sedimentary and diagenetic self-organization. Forward modelling will be used to simulate the effect of gaps in the record produced by each of these processes on diversity and character evolution. This will allow us to answer the questions: What part of diversity do we miss owing to the missing rock record? Are the preserved intervals exceptional or representative? Is there a systematic part of biodiversity and environmental records which will always fall into gaps? By applying the findings of the forward modelling to fossil successions, we will be able to identify and correct for the missing parts of the record and formulate testable hypotheses on the original tempo and mode of evolution at the highest temporal resolution achievable in the geological record.