peat -
Soil formed of dead but not fully decayedplants found in bog areas.
Wikipedia
Peat, or turf, is an accumulation of partially decayed vegetation matter or histosol. Peat forms in wetland bogs, moors, muskegs, pocosins, mires, and peat swamp forests. Peat is harvested as an important source of fuel in certain parts of the world.
OmegaWiki Dictionary
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peat Unconsolidated soil material consisting largely of undecomposed or slightly decomposed organic matter accumulated under conditions of excessive moisture.\n(Source: LANDY)