Mechanism for Burgess Shale-type preservation

Burgess Shale-type preservation of soft-bodied fossils, a phenomenon providing critical insights into early animal diversification, is attributed to unique sedimentologic and geochemical conditions. Research reveals that the exceptional preservation of labile tissues in Cambrian deposits like Chengjiang and Burgess Shale was driven by early inhibition of microbial activity due to oxidant deprivation. This condition arose from low sulfate concentrations in the global ocean and low-oxygen bottom water during deposition, combined with rapid fossil entombment in fine-grained sediments and sealing by carbonate cements at bed tops. These cements, facilitated by unusually high Cambrian seawater alkalinity, created a permeability barrier that restricted oxidant flux, thereby preserving organic remains as carbonaceous compressions. This mechanism, shared across multiple Burgess Shale-type deposits, offers a unique window into the immediate aftermath of the 'Cambrian explosion.'

Gaines, R. R., Hammarlund, E. U., Hou, X., Qi, C., Gabbott, S. E., Zhao, Y., Peng, J., & Canfield, D. E. (2012). Mechanism for Burgess Shale-type preservation. Proceedings of the National Academy of Sciences, 109(14), 5180–5184. https://doi.org/10.1073/pnas.1111784109