The fossils
By adriana
Mold fossil
.
form when sediments bury anorganism and
the sediments change into rock the organism decays leaving a cavity in the shape of the organism.
Cast fossil
-forms when a mold is filled with sand or mud that hardens into the shapeof the organism.
Petrified fossil
Forms when minerals soak into the buried remains, replacing the remains and changing the minto rock (mineralization)
Preserved fossil -Forms when entire organism or parts
of organism are prevented from decaying by being trapped in rock ,ice,tar,or amber.
Carbonized fossil
Forms when organism or parts like leaves ,stems ,flowers,fish ,are pressed between layers of setf mud or clay that hardens savesing almost all the decaying organism away teaving the carbon imprint in the rock.
Trace fossil
-Forms when the mud or sand hardens to stone when a footprint ,trail ,or burrow of an organism was left behind
Index fossil
Index fossil, any animal or plant preserved in the Earth's rocky record that is characteristic of a particular period of geologic time or environment. A useful index fossil should be distinctive or easily recognizable, abundant, and have a wide geographic distribution and short range through time. Index fossils are the basis for defining boundaries on the geologic time scale and for strata correlation. In marine strata, commonly used index fossils include the single-celled Protists with hard body parts and larger forms such as ammonoids. In terrestrial sediments from the Cenozoic Era, which began about 65.5 million years ago, mammals are widely used to date deposits. All of these animal forms have hard body parts, such as shells, bones, and teeth, and they evolved rapidly