The ratio between the heavy and light isotopes of the element in their crystals is not quite right for stuff that has come out of the ground.

它们晶体里重轻同位素的比例并不像是从地底挖出来的东西那样。

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By analysing the isotopic composition of hydrocarbon molecules from plant waxes of the period, he found what looks like a spike in the amount of recently non-biological carbon (which has a distinctive ratio of light isotopes to heavy ones), lasting between 10, 000 and 20, 000 years.

ECONOMIST: A geological burp may have led to the dinosaurs�� domination