3.5 decays/gram/minute of carbon would be produced by a sample 11,460 years old. However, atmospheric testing of nuclear weapons in the late 1950's and early 1960's greatly increased the amount of radiocarbon in the atmosphere, so the decay rate of 14 decays per minute more than doubled.
Here we present a method that makes it possible to obtain both ancient DNA sequences and radiocarbon dates from the same sample material.
Nitrogen atoms high in the atmosphere can be converted to radiocarbon if they are struck by neutrons produced by cosmic ray bombardment.
The rate of bombardment is greatest near the poles, where the Earth's magnetic field is dipping into the Earth and therefore does not deflect incoming cosmic rays.
Once the radiocarbon atom is produced, it rapidly combines with oxygen (OC (7 neutrons) atoms.
Carbon atoms are incorporated into plant tissue (by photosynthesis) then into animal tissue (by ingestion) in nearly the same ratio as in the atmosphere. The Earth's magnetic field, its history, origin and planetary perspective.