Sediment cores are essentially a record of sediments that settled at the sea floor, layer by layer, and they record the conditions of the ocean system during the time they settled.

沉积物岩心主要记录的是沉淀在海底沉积物，一层又一层，记录它们沉淀时的海洋系统状况。

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So did a thick, solid layer of sheep dung covering the floor.

VOA: special.2010.08.03

Methane is the principal component of natural gas, and massive amounts of it are trapped in reservoirs beneath the sea floor and under a layer of the ice-like substance.

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The archaeologists put the shoe's remarkable preservation down to the stable, cool and dry conditions in the cave and the fact that the floor of the cave was covered by a thick layer of sheep dung.

BBC: 'Oldest leather shoe' discovered

The final layer is often panels of loose-weave or sheer fabric hanging in soft drapes to the floor.

WSJ: Sheer Curtains, Solar Shades Are Popular Window Treatments