Structural basin symbol

A closed trace with arrows pointing inward all round.

Also known as: Basin structure symbol, Structural low symbol

Maps & navigationScientificStandard profile

Meanings

On a geological map a structural basin is drawn as a closed axial trace with arrows pointing inward, marking strata dipping towards a centre from every direction.

Officially standardisedVerified fact
Marks strata dipping inward towards a central point from all directions.
Contexts: Maps
Common modern usageVerified fact
Is the closed equivalent of a syncline and holds the youngest rocks at its centre, completing the four-way set with the dome.
Contexts: Maps

Visual description

A roughly circular closed line with short arrows around it all pointing towards the enclosed centre.

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

Geologic map
Wikipedia · retrieved 2026-08-24
Tertiary reference. Used for how a structural symbol is read and for the plain-language name of a feature. Structural definitions follow the cartographic standard.
FGDC Digital Cartographic Standard for Geologic Map Symbolization
United States Geological Survey for the Federal Geographic Data Committee · retrieved 2026-08-24
An openly published national standard defining geologic map symbols, lithologic patterns and their colours. The definitive source for these records. It is a United States standard; other national surveys use related but not identical patterns, and records say so rather than presenting one national convention as universal.

Last reviewed 2026-08-24

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Meanings

On a geological map a structural basin is drawn as a closed axial trace with arrows pointing inward, marking strata dipping towards a centre from every direction.

Officially standardisedVerified fact

Marks strata dipping inward towards a central point from all directions.

Contexts: Maps

Common modern usageVerified fact

Is the closed equivalent of a syncline and holds the youngest rocks at its centre, completing the four-way set with the dome.

Contexts: 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

Geologic map
Wikipedia · retrieved 2026-08-24
Tertiary reference. Used for how a structural symbol is read and for the plain-language name of a feature. Structural definitions follow the cartographic standard.
FGDC Digital Cartographic Standard for Geologic Map Symbolization
United States Geological Survey for the Federal Geographic Data Committee · retrieved 2026-08-24
An openly published national standard defining geologic map symbols, lithologic patterns and their colours. The definitive source for these records. It is a United States standard; other national surveys use related but not identical patterns, and records say so rather than presenting one national convention as universal.

Last reviewed 2026-08-24