dirt-bed Geol.
A stratum consisting of ancient vegetable mould; spec. A bed of dark bituminous earth containing the stumps of trees, occurring in the lower Purbeck series of the Isle of Portland, and overlying the Portland oolite.
| 1824 T. Webster in Geol. Trans. (1829) II. 42 A bed about one foot thick, consisting of a dark-brown substance, and containing much earthy lignite; this bed is very remarkable and extends all through the north end of the Isle of Portland..It is called by the quarrymen the Dirtbed. 1836 Buckland Geol. xviii. §3. (1858) 457 A single stump rooted in the dirt-bed in the Isle of Portland. 1851 Richardson Geol. (1855) 397 A mass of bituminous earth, called the ‘dirt-bed’, which is an ancient vegatable soil, containing numerous trunks of fossil trees, standing erect at a height of from one to three feet, with their summits jagged. |