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Study questions carbon dating

This chemical change is an expression of diagenesis.Often what remains is a carbonaceous film known as a phytoleim, in which case the fossil is known as a compression.Minerals precipitate from the groundwater, occupying the empty spaces.This process can occur in very small spaces, such as within the cell wall of a plant cell.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.The development of radiometric dating techniques in the early 20th century allowed scientists to quantitatively measure the absolute ages of rocks and the fossils they host.For instance, when the rock is broken open, the phytoleim will often be attached to one part (compression), whereas the counterpart will just be an impression.For this reason, one term covers the two modes of preservation: adpression.

to dinosaurs and trees, many meters long and weighing many tons.Because of their antiquity, an unexpected exception to the alteration of an organism's tissues by chemical reduction of the complex organic molecules during fossilization has been the discovery of soft tissue in dinosaur fossils, including blood vessels, and the isolation of proteins and evidence for DNA fragments.In 2014, Mary Schweitzer and her colleagues reported the presence of iron particles (goethite-a Fe O(OH)) associated with soft tissues recovered from dinosaur fossils.Small scale permineralization can produce very detailed fossils.For permineralization to occur, the organism must become covered by sediment soon after death or soon after the initial decay process.Paleontology is the study of fossils: their age, method of formation, and evolutionary significance.Specimens are usually considered to be fossils if they are over 10,000 years old.An endocast or internal mold is formed when sediments or minerals fill the internal cavity of an organism, such as the inside of a bivalve or snail or the hollow of a skull. If the chemistry is right, the organism (or fragment of organism) can act as a nucleus for the precipitation of minerals such as siderite, resulting in a nodule forming around it.If this happens rapidly before significant decay to the organic tissue, very fine three-dimensional morphological detail can be preserved.Often, however, the phytoleim is lost and all that remains is an impression of the organism in the rock—an impression fossil.In many cases, however, compressions and impressions occur together.

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