Global accretionary orogenesis triggered the Cambrian Explosion of life

Abstract The Cambrian Explosion (541-515 Myr ago) is arguably the most significant evolutionary transition after the origin of life1-2. A variety of environmental perturbations have been correlated to this rapid animal species diversification1-3. Increased weathering fluxes from the continents to the oceans are hypothesized to cause these perturbations4-6, but why such enhanced weathering occurred is unknown. We document two newly discovered eclogite occurrences within the Central Asian Orogenic Belt (CAOB). These eclogites recorded Cambrian deep subduction of continental crust and consequent mountain building during arc-continent collisions concomitant to the Cambrian Explosion. Correlative metamorphic belts of the same age occur across the CAOB indicating a continental subduction front (>3,500 km) larger than that of the modern Himalaya. The CAOB, along with Gondwana’s peripheral orogens, provide a unique and unrecognized global accretionary orogen (>18,500 km) for the Cambrian Earth, larger than the so-far recognized Cambrian collisional orogen during Gondwana assembly4. Our biogeochemical modelling results suggest that the increased weathering of phosphorus from these accretionary orogenic belts would stimulate marine primary productivity, increase atmospheric O2, and promote the expansion of shallow-ocean oxygenation at a time coincident with the Cambrian Explosion.