The preservational mode of the Doushantuo formation involves very early phosphatisation on a cellular level - with cells being replaced by phosphate before they degrade.^[1]

Occurrence

The mode of preservation is typically found in shallow, high energy waters, as lenses of phosphate in carbonate rocks.^[1] Its occurrence is assisted by high concentrations of phosphate, which are presumably led to precipitate around the degradation products of cells and cell walls.^[1]

What is preserved

Cells are preserved at a cellular level, with arguments that sub-cellular structures may even represent cell nuclei.

Bias

Although the preservational window is open pretty continually from about 580 million years ago^{[verification needed]} through most of the Cambrian, it tends to preserve microscopic things, such as embryos and bacteria.^[1]