Geochemical and mineralogical insight into the environmental conditions for preservation of the Chengjiang biota

摘要

The Chengjiang biota is unique in the geological record because of their position after the Precambrian-Cambrian transition and before the earliest evidence of land-dwelling organisms. The deposit represents one of the few fossiliferous deposits exhibiting extraordinarily well-preserved examples of biota including soft-bodied animals and soft body parts of animals. The major element chemical composition of horizons containing soft-bodied fossils is typical of marine shales. Minor element concentration ratios suggest the sediments were deposited in suboxic conditions. The occurrence of nontronite in the sediments restricts the thermal environment following deposition to below 70°C. These restrictions could be met by rapid deposition of fine-grained sediments of volcanic origin at slightly elevated temperatures.