Some corals can be carbon dated, and also dated by another radioactive material, Thorium-230.Pollen found in the Greenland icecap has been carbon dated, and also dated by counting ice layers. Trees grow a thick ring in a good year, and grow a thin ring in a bad year.On the Web, you could visit a dating laboratory, visit a dating service, read an encyclopedia entry or read a critique.The Lake Suigetsu varve calibration was reported by ABC News and was published: Atmospheric Radiocarbon Calibration to 45,000 yr B.When this was first done, it turned out that carbon dating had been giving too-young dates for early civilizations.Apparently, the production of C14 by the Sun has changed by several percent across the last 10,000 years.
However, carbon dating has done well on young material like the Dead Sea Scrolls, the Minoan ruins, and acacia wood from the tomb of the pharoah Zoser.For example, Stonehenge suddenly became older than the Pyramids, instead of younger.Since then, several other calibrations have been done, which confirm and extend the tree-ring one. It is produced in the upper atmosphere by radiation from the sun.(Specifically, neutrons hit nitrogen-14 atoms and transmute them to carbon.) Land plants, such as trees, get their carbon from carbon dioxide in the air. The same is true of any creature that gets its carbon by eating such plants. Suppose such a creature dies, and the body is preserved.