The black unit including a biotic extinction was caused by oceanic anoxic event. Crisis that deepwater keeled foraminifera encountered represents a ferocious anoxia in deep marine environment .
黑层段是大洋缺氧造成的结果，生物大量灭绝，深层水具旋脊有孔虫的所遭受的危机反映出当时海洋深层水体严重缺氧的特征；
Marine transgression resulted in the forming of swamp and then the peat swamp. And the transgression later on put the peat formed in advance in deep water environment to form coal in the end.
海侵导致了陆表海盆地沼泽环境的形成，进而形成泥炭沼泽，而随后的海侵事件导致了先形成的泥炭迅速处于深水环境最终成煤。
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