Fossilization of Soft Tissue in the Laboratory

TLDR

Soft‑tissue fossils often preserve cellular details through calcium‑phosphate replacement, a process traditionally thought to require high phosphate concentrations in sediment pore waters, especially under anoxic, closed conditions. Decay experiments showed that modern shrimps mineralize in amorphous calcium phosphate within two weeks under anoxic conditions, preserving muscle cellular detail and halting normal soft‑tissue degradation.

Abstract

Some of the most remarkable fossils preserve cellular details of soft tissues. In many of these, the tissues have been replaced by calcium phosphate. This process has been assumed to require elevated concentrations of phosphate in sediment pore waters. In decay experiments modern shrimps became partially mineralized in amorphous calcium phosphate, preserving cellular details of muscle tissue, particularly in a system closed to oxygen. The source for the formation of calcium phosphate was the shrimp itself. Mineralization, which was accompanied by a drop in pH, commenced within 2 weeks and increased in extent for at least 4 to 8 weeks. This mechanism halts the normal loss of detail of soft-tissue morphology before fossilization. Similar closed conditions would prevail where organisms are rapidly overgrown by microbial mats.