Geochronological dating scryed dating quizzes
After showing the essential uniformity of carbon-14 in living material, Libby sought to answer the second question by measuring the radiocarbon level in organic samples dated historically—materials as old as 5,000 years from sources such as Egyptian tombs.With correction for radioactive decay during the intervening years, such old samples hopefully would show the same starting carbon-14 level as exists today. His conclusion was that over the past 5,000 years the carbon-14 level in living materials has remained constant within the 5 percent precision of measurement.Ages of geological formations or secondary events (i.e.
Natural contamination of chemical sediments with detrital material can also affect the results of dating of diagenesis.
There are some techniques and calculations which can "look through" the post formation event.
The occasional exceptions all involve nonatmospheric contributions of carbon-14-depleted carbon dioxide to organic synthesis.
Specifically, volcanic carbon dioxide is known to depress the carbon-14 level of nearby vegetation, and dissolved limestone carbonate occasionally has a similar effect on freshwater mollusks, as does upwelling of deep ocean water on marine mollusks.
In every case, the living material affected gives the appearance of built-in age.