Most rock sequences that straddle the end of the permian are either incomplete or hard to date .
大部分跨越了二叠纪的岩序列不是不够完整就是很难确定日期。
The affinity of associated elements in permian coals from the huaibei coalfield .
淮北煤田二叠纪煤中伴生元素的亲和性研究。
Some 250 million years ago , at the end of the time known as the permian , life was all but wiped out during a sustained period of massive volcanic eruption and devastating global warming .
