Discovering Fossils 10-30

Several months pass and all that remains of the buried fish is its skeleton.


                           Sediment accumulation and permineralisation
Over time the skeleton is gradually buried deeper by accumulating sediment. Slowly the weight of the sediment compacts the underlying areas, pressing the grains together, driving excess water out, and depositing minerals in the pores, and ultimately turning the soft sediment to hard rock - a process known as lithification.
As this process takes place, minerals contained within the waters-saturated sediment replace the original minerals in the skeleton and fill any voids formed as parts of the skeleton dissolve. The process of mineral replacement is known as permineralisation and results in a remineralised copy of the original skeleton.