这一次是碳同位素泄露了秘密。

This time, it is carbon isotopes that give the game away.

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经过了上千年，这两种碳同位素的比例一直是不变的。

For thousands of years, the ratio between the two has been the same.

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随之而来勃发的浮游生物吸走了12c，碳同位素比率转向相反方向。

The subsequent plankton bloom sucked up the 12c and the isotope ratio veered off in the opposite direction.

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