The shale was deposited in an oxygen-deficient lake where lethal gases sometimes bubbled up and killed animals.

页岩沉积在一个缺氧的湖泊里，那里有时会冒出致命的气体，杀死动物。

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The shale was deposited in an oxygen-deficient lake where lethal gases sometimes bubbled up and killed animals.

页岩沉积在一个缺氧的湖泊里，那里有时会冒出致命的气体，杀死动物。

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