The 5th International Conference of Geobiology

The silicon cycle on the Earth’s surface is closely associated with the carbon cycle via the continental weathering, reverse weathering and the co-burial process of silica-rich and carbon-rich organisms. There is a global chert accumulation event during the Permian period - Permian Chert Event (~280 Ma to 251 Ma), indicating large perturbations in the marine silicon cycle. The Permian also witnessed termination of late Paleozoic ice age (~340 Ma to ~260 Ma), final assembly of the Pangea supercontinent and significant changes in biosphere. However, few studies have been focused on using these cherts to understand the marine silicon cycle during this major environmental and climatic transition period. Here, we study the petrology, mineralogy, oxygen and silicon isotopes of widespread cherts formed from ~280 to 253 Ma. Our results support that these studied Permian cherts are biogenic in origin. New and compiled silicon isotope data of biogenic cherts from South China exhibit relatively higher δ³⁰Si values during warm stages and low values during cold stage, indicating increased and decreased marine siliceous productivity during warm and cold stages, respectively. Our study provides a typical example of interpreting changes of silicon isotopes in biogenic cherts through major climatic transition period in terms of changes of oceanic siliceous biological productivity and provide insights into Permian marine silicon cycle during the termination process of late Paleozoic ice age.

 

Permian Chert Event, Late Paleozoic ice age, Silicon isotopes, Biogenic cherts, Marine siliceous productivity