Fossilization
The rare sequence of processes that preserves remains or traces of ancient organisms in the rock record.
Fossils are the preserved remains or traces of ancient organisms, and fossilization is the set of processes that produce them. The term covers body fossils — shells, bones, teeth, wood — and trace fossils such as footprints, burrows, and coprolites. Fossilization is rare: most organisms decompose completely or are consumed by scavengers before any preservation can begin.
Taphonomy is the study of everything that happens between death and discovery. The typical pathway begins when an organism dies near a body of water and is buried rapidly by sediment, protecting its hard parts from scavengers and aerobic decay. Permineralization then occurs when mineral-rich groundwater precipitates minerals — commonly silica, calcite, or iron compounds — into the pores of bone or wood, preserving their structure in detail. Molds and casts form when remains dissolve away, leaving a cavity that later fills with sediment or minerals. Exceptional deposits such as amber, ice, and tar pits preserve soft tissues that are normally lost.
The fossil record is therefore systematically biased: organisms with hard shells or skeletons and environments with rapid burial are overrepresented, while soft-bodied organisms are rarely preserved. These gaps are part of the record itself, and paleontologists interpret abundance patterns with them in mind.
Despite the bias, fossils provide the empirical foundation of the geological time scale and of biostratigraphy — dating and correlating rock layers by their fossil content. The oldest widely accepted fossils are stromatolites, layered microbial structures over 3 billion years old, and the sequence of forms through younger strata documents how life changed across hundreds of millions of years.
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earth science fossils geology paleontology taphonomy
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