Sedimentology
The whole sequence sits on an unconformity with the underlying Liantuo Formation, which is free of fossils, an unconformity usually being interpreted as a period of erosion. On that unconformity lie tillites of the Nantuo Formation - cemented glacial till formed of glacial deposits of cobbles and gravel laid down at the end of the Marinoan / Varangian glaciation (the third and last of a series of very extensive glaciations during a period called the Cryogenian -- ('Snowball Earth'). This latest Cryogenian glacial level is tentatively dated ca 654 (660 ± 5) — 635 Ma (million years ago).
The Doushantuo formation itself has three layers representing aquatic sediments that formed as sea levels rose with the melting of worldwide glaciation. Biomarkers indicate highly saline conditions, such as might be found in a lagoon, low oxygen levels, and very little sediment that had been washed off land surfaces.
The richest finds (the Lagerstätte itself) lie at the bottom of the middle stratum, with a date about 570 Ma, thus from some time after the great Gaskiers glaciation of .
Read more about this topic: Doushantuo Formation