hoofdlagen

Hoofdlagen is a Dutch term used to refer to the principal layers within a natural or engineered system. In geology, hoofdlagen denote lithostratigraphic units that represent the main, distinct layers of rock within a formation. They are characterized by a coherent lithology, thickness, and fossil content, and are used to describe and map the vertical and lateral arrangement of rocks.

In practice, a hoofdlagen serves as a reference framework for correlation across a region. Boundaries between hoofdlagen are contacts, which can be conformable or unconformable, indicating continuous deposition or gaps in time. In sedimentary basins, hoofdlagen reflect changes in depositional environments (for example, marine to deltaic) and can be subdivided into sub-hoofdlagen to capture finer lithological variation. They are named after type sections, most characteristic exposures, or geographic localities.

In soil science, though less common, the term can describe the principal horizons of a soil profile, such as the organic-rich top layer and lower mineral layers, used for fertility and management assessments. Etymology: from Dutch hoofd meaning main, and laag meaning layer.

Relation to other concepts: lithostratigraphy studies hoofdlagen; sequence stratigraphy considers temporal relationships between them; in engineering, recognizing hoofdlagen helps in groundwater or construction planning.