Soil mark
Soil marks are differences in soil colour as a result of archaeological features
Feature (archaeology)
Feature in archaeology and especially excavation has several different but allied meanings. A feature is a collection of one or more contexts representing some human non-portable activity that generally has a vertical characteristic to it in relation to site stratigraphy. Examples of features are...

. They can be seen when a ploughed out earthwork
Earthworks (archaeology)
In archaeology, earthwork is a general term to describe artificial changes in land level. Earthworks are often known colloquially as 'lumps and bumps'. Earthworks can themselves be archaeological features or they can show features beneath the surface...

has left hard dry material of a former bank and damper wetter material from a former ditch. They can also occur when a feature has cut through the top soil to reveal underlying chalk.
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