The leaves of ferns, reeds, and other plants, are frequently found between layers of shale or slaty clay, beautifully perfect, but converted into coal.

我们通常能在页岩层和黏板岩层中发现蕨类植物，芦苇和其它植物的叶子，但是这些叶子都完全转变为了煤。

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But Dr Kharaka nevertheless suggests that the sequestration of carbon dioxide should be confined to deep aquifers, where overlying layers of shale would be likely to prevent leaks.

但是，Kharaka博士依然建议，二氧化碳的固存应该局限于深蓄水层，这些蓄水层上方有很多层页岩叠加在一起，可以防止泄漏。

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The geochemical characteristics of dark gray mudstone and shale in evaporite layers record the sedimentary environment of salt lake.

蒸发岩夹层中的深灰色泥岩和页岩的地球化学特征充分体现了盐湖沉积环境标志。

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The technique they developed, called hydraulic fracking, involves drilling 5, 000-9, 000 feet below ground (in the Marcellus shale), and then moving horizontally into the layers of shale rock where the hydrocarbons lie.

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Although methane itself is not regulated as a water pollutant, the study could lead to federal regulation of the heretofore largely unregulated practice of the hydraulic fracturing, or fracking, of deep layers of shale to tap vast reservoirs of natural gas in the United States.

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Advances in drilling technologies in the last decade have enabled energy companies to tap huge supplies of gas locked up in shale thin layers of rock a mile or more underground that reach for miles across the landscape.

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