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Unconformity identification and geology

A buried erosion surface or non-depositional surface separating two rock units of significantly different ages, representing a gap in the geological record. Three main types exist: angular unconformity tilted/folded strata below, horizontal above , disconformity parallel strata above and below, but with a time gap , and nonconformity sedimentary rocks overlying igneous or metamorphic basement . Unconformities record episodes of uplift, erosion, or non-deposition. Field: stratigraphy. Example: Hutton's Unconformity at Siccar Point, Scotland, where horizontal Devonian sandstone rests on vertical Silurian greywacke, was a key observation in James Hutton's 1788 recognition of deep geological time.. Related terms: Angular unconformity, Disconformity, Nonconformity, Hiatus.

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Sources, scope & corrections

These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.

Editorial owner
GeoMiner
Last updated
2026-03-30T15:19:42.096023+00:00
Review status
Published; not independently peer-reviewed
  • USGS Thesaurus — U.S. Geological Survey. Controlled earth-science terminology used to describe USGS information resources.
  • Glossary of Geologic Terms — U.S. National Park Service. Geologic definitions prepared by the NPS Geologic Resources Inventory.

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Common questions

What does Unconformity mean in geology?
A buried erosion surface or non-depositional surface separating two rock units of significantly different ages, representing a gap in the geological record. Three main types exist: angular unconformity tilted/folded strata below, horizontal above , disconformity parallel strata above and below, but with a time gap , and nonconformity sedimentary rocks overlying igneous or metamorphic basement . Unconformities record episodes of uplift, erosion, or non-deposition.
What is an example of Unconformity?
Hutton's Unconformity at Siccar Point, Scotland, where horizontal Devonian sandstone rests on vertical Silurian greywacke, was a key observation in James Hutton's 1788 recognition of deep geological time.
Which earth-science field uses the term Unconformity?
Unconformity is used in stratigraphy.
Which terms are related to Unconformity?
Related terms in this reference are Angular unconformity, Disconformity, Nonconformity, Hiatus.

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