Radiocarbon dating of east america lake levels Web viedochat es
Spurious radiocarbon dates caused by volcanic emanations of radiocarbon-depleted CO2 probably also come under the category of reservoir corrections.Plants which grow in the vicinity of active volcanic fumeroles will yield a radiocarbon age which is too old. (1980) measured the radioactivity of modern plants growing near hot springs heated by volcanic rocks in western Germany and demonstrated a deficiency in radiocarbon of up to 1500 years through comparison with modern atmospheric radiocarbon levels.We think that the rapid burial of the plants within the shell-bearing sand provided a high p H, and that the tsunami deposit was subsequently sealed with marine silt preventing it from oxygen and light.The green-colored moss cannot have been re-deposited, but must have been alive when the tsunami struck the coast.
In such a case, it is very difficult to ascertain the precise reservoir difference and hence apply a correction to the measured radiocarbon age.Unexpectedly, we discovered plant material within the tsunami sand that is excellent for radiocarbon dating - these are green moss stems that we know were killed by the tsunami. Chlorophyll in dead plants degrades rapidly with exposure to light and oxygen.The reason to why the chlorophyll is still present in these 8000-year-old moss stems is surprising.The average difference between a radiocarbon date of a terrestrial sample such as a tree, and a shell from the marine environment is about 400 radiocarbon years (see Stuiver and Braziunas, 1993).This apparent age of oceanic water is caused both by the delay in exchange rates between atmospheric CO2 and ocean bicarbonate, and the dilution effect caused by the mixing of surface waters with upwelled deep waters which are very old (Mangerud 1972).