Contact Relationships

Understanding contact relationships is critical for interpreting geological history. Contact Types Sharp Contacts - Intrusive contacts: igneous rock cuts host - Faulted contacts: displacement evident - Unconformities: erosional surface Gradational Contacts - Metamorphic grade changes - Facies transitions - Alteration halos Age Relationships Cross-Cutting Principle Feature that cuts another is younger. Inclusions Inclusions are older than host rock. Documentation Describe contacts by: - Type sharp, gradational - Orientation strike/dip - Width of transition zone - Associated features alteration, veining

All lessons in Field Mapping — Return to the complete Field Mapping course outline.
Previous lesson: Outcrop Description — Systematic outcrop description ensures consistent, complete documentation. Description Sequence Follow a consistent order: 1. Rock type and name 2.
Next lesson: Structural Measurements — Structural geology measurements document the orientation and character of deformation features. Planar Features Bedding Primary sedimentary layering.

Verification resources

Cross-check terminology, classification, methods, and safety with these authoritative external resources.

Geoscience maps — Natural Resources Canada. Government bedrock, surficial, geochemical, glacial, and hazard map resources.
National Geologic Map Database — U.S. Geological Survey. Geologic maps, reports, standards, and mapping resources from geological surveys.

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Contact Relationships

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Verification resources