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What is relative dating of rocks and fossils

what is relative dating of rocks and fossils-40

The totality of fossils is known as the fossil record.

Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, hair, petrified wood, oil, coal, and DNA dinosaurs and trees, many meters long and weighing many tons.A fossil normally preserves only a portion of the deceased organism, usually that portion that was partially mineralized during life, such as the bones and teeth of vertebrates, or the chitinous or calcareous exoskeletons of invertebrates.Specimens are usually considered to be fossils if they are over 10,000 years old.The observation in the 19th century that certain fossils were associated with certain rock strata led to the recognition of a geological timescale and the relative ages of different fossils.This process can occur in very small spaces, such as within the cell wall of a plant cell.

Small scale permineralization can produce very detailed fossils.

A shell is said to be recrystallized when the original skeletal compounds are still present but in a different crystal form, as from aragonite to calcite.

Compression fossils, such as those of fossil ferns, are the result of chemical reduction of the complex organic molecules composing the organism's tissues.

Some fossils are biochemical and are called chemofossils or biosignatures.

Permineralization is a process of fossilization that occurs when an organism is buried.

The empty spaces within an organism (spaces filled with liquid or gas during life) become filled with mineral-rich groundwater.