| Sediment
Floodplain deposits near Novyi Ierusalim, Russia
Both geology and palaeontology are so preoccupied with the workings of the sea realm, that one might wonder, is nothing ever preserved of the familiar world, of the animals we associate the most with – is nothing left of firm ground?
Firm ground is recognised in geology as a surface of non-deposition. It is defined by a negative, because it is not a layer, but a plane.
The geological metaphor for time is thickness. Since firm ground is a surface of non-deposition, it has no thickness. Soils do not grow up, they do not grow much down – time is manifested in the density of biogenic structures, commonly, burrows (cf. Bromley 1975).
