1. Freezing, drying and wrapping, such as in tar or resin, can produce whole-body fossils that preserve body tissues.
When most creatures change in various other ways, they become fossils.
Heat and pressure buried in sediments sometimes cause biological tissues, including plant leaves and soft parts of fish, reptiles and marine invertebrates, to release hydrogen and oxygen, leaving carbon residues? .
This process, called carbonization or distillation, produces detailed carbon prints of dead organisms in sedimentary rocks.
The most common petrochemical method is called mineralization or petrochemical. After the soft tissues of organisms rot in sediments, the hard parts, especially the bones, are forgotten.
2. Water seeps into the debris, and minerals dissolved in the water seep into the space inside the debris to form crystals. These crystalline minerals harden the debris together with the surrounding sedimentary rocks? .
In another fossilization process called substitution, after water completely dissolves the original hard parts of living things, minerals in groundwater replace the minerals that make up the body remains.
Fossils also come from molds and castings. If organisms are completely dissolved in sedimentary rocks, they will leave external impressions on the rocks, which are called external molds. If that mold is filled with other minerals, it becomes a casting.
3. When sediments or minerals fill the internal cavities of organisms (such as shells or skulls), internal molds will be formed and the residues will be dissolved.
Organic residue
In recent years, researchers have found that some fossils are not just minerals. For example, fossil analysis shows that it is owned? The Cretaceous organic matter was from 65.5 million years to 654.38+45.5 million years, and the Jurassic organic matter was from 654.38+45.5 million years to 654.38+99.6 million years.
Tests show that these organic substances belong to dinosaurs because they match some protein of birds that evolved from dinosaurs.