dirt-bed

Above this bed lie those which have been called the Wealden, from their full development in the Weald of Sussex; and these as incontestably argue that the dry land forming the dirt-bed had next afterwards become the area of brackish estuaries, or lakes partially connected with the sea; for the Wealden strata contain exuviae of fresh-water tribes, besides those of the great saurians and chelonia.

Vestiges of the Natural History of Creation Robert Chambers 1836

The dirt-bed contains exuviae of tropical trees, accumulated through time, as the forest shed its honours on the spot where it grew, and became itself decayed.

Vestiges of the Natural History of Creation Robert Chambers 1836