Soil horizon C designation

A letter marking little-altered parent material.

Also known as: Parent material designation, Unaltered substratum

Historical & archaeologicalScientificStandard profile

Meanings

The soil survey designation for a horizon of parent material little altered by soil-forming processes.

Officially standardisedVerified fact
Designates a horizon of parent material little altered by soil-forming processes.
Contexts: Technical drawing, Maps
Officially standardisedVerified fact
Closes the sequence at the point where soil stops and geology begins, so the letter marks a boundary between two disciplines as much as between two layers.
Contexts: Technical drawing, Maps

Visual description

A capital letter written against the lowest drawn layer of a soil profile.

Symmetry: none
Orientation: upright

Confidence

IdentityHigh confidence: High confidence because the identity is documented in encyclopedic references.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is documented in encyclopedic references.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references.

Sources

Standard and guidance for archaeological field evaluation and excavation
Chartered Institute for Archaeologists · retrieved 2026-08-25
The professional standard for archaeological field recording in the United Kingdom, cited for recording conventions and the structure of a site archive. Practice differs between countries and between units, and records say where a convention is not universal.
Soil Survey Manual, horizon designation and texture classification
United States Department of Agriculture · retrieved 2026-08-25
The manual defining soil horizon letter designations and the texture triangle. Cited for what a designation means. Other national systems use different letters and records say where a convention is not universal.

Last reviewed 2026-08-25

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Meanings

The soil survey designation for a horizon of parent material little altered by soil-forming processes.

Officially standardisedVerified fact

Designates a horizon of parent material little altered by soil-forming processes.

Contexts: Technical drawing, Maps

Officially standardisedVerified fact

Closes the sequence at the point where soil stops and geology begins, so the letter marks a boundary between two disciplines as much as between two layers.

Contexts: Technical drawing, Maps

Confidence

IdentityHigh confidence: High confidence because the identity is documented in encyclopedic references.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is documented in encyclopedic references.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references.

Sources

Standard and guidance for archaeological field evaluation and excavation
Chartered Institute for Archaeologists · retrieved 2026-08-25
The professional standard for archaeological field recording in the United Kingdom, cited for recording conventions and the structure of a site archive. Practice differs between countries and between units, and records say where a convention is not universal.
Soil Survey Manual, horizon designation and texture classification
United States Department of Agriculture · retrieved 2026-08-25
The manual defining soil horizon letter designations and the texture triangle. Cited for what a designation means. Other national systems use different letters and records say where a convention is not universal.

Last reviewed 2026-08-25