In a stratigraphical context objects closer to the surface are more recent in time relative to items deeper in the ground.
A bottle of whiskey masquerading as an 1856 Macallan Rare Reserve, which could have sold for tens of thousands of dollars, had to be withdrawn from a Christie’s auction because its origin was determined as being sometime after 1950.
A surprising characteristic revealed the true age of the malt: radioactive particles.
Nuclear weapons testing brought about a reaction that simulated atmospheric production of carbon 14 in unnatural quantities.
The huge thermal neutron flux produced by nuclear bombs reacted with nitrogen atoms present in the atmosphere to form carbon 14.
The carbon 14 produced is what is known as bomb carbon or artificial radiocarbon.