Data from: Decaying of Artemia salina in clay colloids: 14-month experimental formation of subfossils

The mechanism that guides the formation of exceptionally preserved fossils
with soft tissues variously displayed is a paramount challenge to
paleontology. The key question for exceptional preservation is the nature
of the slowdown of decay and acceleration of soft tissue mineralization.
Here we report the experimental formation of subfossils of the brine
shrimp Artemia salina (Crustacea, Branchiopoda), which were produced
during 14 months of aging in a kaolinite clay sediment. EDS/SEM elemental
analyses showed that the subfossils were preserved as thin clay-organic
replicas that displayed fine anatomical details. Decomposition in the
clay-colloidal solution established highly heterogeneous acidic
conditions, with the lowest pH typically found in the vicinity of the
buried organisms, and visually manifested in patchy coloration of the
sediment. Elevated acidity is likely what ultimately slowed the decay. An
acidic environment increases the rate of clay destruction and,
consequently, the diffusion rate decline. As a result, the acidic products
quickly accumulate around a buried body; this in turn inhibits bacterial
proliferation, accelerates the acidic hydrolysis of clay and, accordingly,
the release of tanning and mineralizing agents. The subfossils remained
stable under experimental high pressure and temperature. These model
subfossils exhibit features that are typical of some Lagerstätten fossils
preserved in fine-grained sediments.