The Punctuated evolution of the Earth: geodynamic constraints and model predictions

The preserved Precambrian crustal record is strongly episodic, and observation that has been attributed to preservational effects or episodic crustal production. These age peaks are associated with juvenile crustal production, voluminous high-temperature volcanism, massive mantle depletion, widespread orogeny and mineralisation, large apparent polar wander velocity spikes, and subsequent paleointensity increases. The impact of these events impinged on the glaciation record, atmospheric and ocean chemistry, and on the rise of oxygen. Here we assess a variety of geodynamic models for Precambrian dynamics against the swath of observational constraints available. We find that episodic behaviour from non-linear slab-driven models - such as mantle avalanches or episodic subduction events - are best able to simultaneously satisfy the majority of geological constraints. In such models, rapid descent of subducted material into the mantle drives fast plate motions and convergence at the surface. This is accompanied by large-scale upwellings of deep hot mantle which contribute to voluminous volcanism. Currently, it is not possible to differentiate the ultimate cause of non-linear plate behaviour solely from the geological record, however, dynamic simulations under Earth-like conditions may be able to secern.