The atmosphere in the ancient world was different, most likely, as some scientists have indicated. (this thread may go in coffee house, or the science or faith, etc, because I would make reference to a pre flood atmosphere). I would propose that maybe there was a lot of argon in that atmosphere. The evidence for which is the amount of the gas in ancient rock, particualily old lava. These days, when lava say, forms an island, or formation, we can see it has less argon. The gas is assumed (?) to have formed from a long process, however, because we know it does break down eventually to this very gas. But if it was deposited by a pre flood atmosphere rich in argon, or, if a quick atmosphere change at the flood time resulted in a lot being introduced quickly, would this not account for it!?
Therefore, rather than age, it is only an indicator of post, or pre (or mid) flood gas entering things like lava.
Here is a few quotes on the topic
"(Ar), chemical element, inert gas of Group 0 (noble gases) of the periodic table, terrestrially the most abundant and industrially the most frequently used of the noble gases. Colourless, odourless, and tasteless, argon gas was isolated (1894) from air by the British scientists Lord Rayleigh and Sir William Ramsay. Henry Cavendish, while investigating atmospheric nitrogen ("phlogisticated air"), had concluded in 1785 that not more than 1/120 part of air might be some inert constituent. His work was forgotten until Lord Rayleigh, more than a century later, found that nitrogen prepared by removing oxygen from air is always about 0.5 percent more dense than nitrogen derived from chemical sources such as ammonia. The heavier gas remaining after both oxygen and nitrogen had been removed from air was the first of the noble gases to be discovered on Earth and was named argon because of its chemical inertness. (Helium had been spectroscopically detected in the Sun in 1868.)
Argon constitutes 1.3 percent of the atmosphere by weight and 0.94 percent by volume and is found occluded in rocks. A major portion of terrestrial argon has been produced, since the Earth's formation, in potassium-containing minerals by decay of the rare, naturally radioactive isotope potassium-40. The gas slowly leaks into the atmosphere from the rocks in which it is still
being formed. The production of argon-40 from potassium-40 decay is utilized as a means of determining the Earth's age (potassium-argon dating). "
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So many ideas, so little time!