Fossils dating rock
The embedding of insects in amber (a process called resin fossilization) and the preservation of the carcasses of Pleistocene mammoths in ice are rare but striking examples of the fossil preservation of soft tissues.
Leaves, stems, and other vegetable matter may be preserved through the process of carbonization, where such parts are flattened between two layers of rock.
In such sequences of layers in different geographic locations, the same, or similar, fossil floras or faunas occur in the identical order.
By comparing overlapping sequences, it is possible to build up a continuous record of faunas and floras that have progressively more in common with present-day life forms as the top of the sequence is approached.fossil record has provided important information for at least four different purposes.
Unearthing the specimen from the rock is often painstaking work that includes labeling each part of the specimen and cataloging the location of each part within the rock.
By contrast, the soft parts of animals or plants are very rarely preserved.
Solutions may fill the interstices, or pores, of the shell or bone with calcium carbonate or other mineral salts and thus fossilize the remains, in a process known as permineralization.
In other cases there may be a total replacement of the original skeletal material by other mineral matter, a process known as mineralization, or replacement.
In recent years, geologists have been able to study the subsurface stratigraphy of oil and natural gas deposits by analyzing microfossils obtained from core samples of deep borings.
Fossil collection as performed by paleontologists, geologists, and other scientists typically involves a rigorous excavation and documentation process.
The progressive changes observed within an animal group are used to describe the evolution of that group.