What defines a geological formation?

A geological formation is a fundamental unit of lithostratigraphy consisting of a body of rock with consistent physical characteristics. These rock layers must be large enough to be mapped at the surface or traced in the subsurface. The concept originated with Abraham Gottlob Werner in the late eighteenth and early nineteenth centuries.

What we know

• A geological formation is a body of rock having a consistent set of physical characteristics that distinguishes it from adjacent bodies of rock. [1, 2]
• Formations must be large enough to be mapped at the surface or traced in the subsurface. [1, 2]
• The term goes back to the beginnings of modern scientific geology, used by Abraham Gottlob Werner in his theory of the origin of the Earth between 1774 and 1817. [2]
• Geological formations are usually, but not universally, tabular in form and can consist of a single lithology or a heterogeneous mixture of lithologies. [1, 2]

Where to go next

• the bigger pictureHow are rock layers studied in stratigraphy?
• a case in pointHow do hoodoos form from rock layers?
• whoWhat role did Abraham Gottlob Werner play in geology?
• what followedHow do geological maps help predict mineral resources?
• compared withHow does a geological formation differ from a topographic rock formation?
• an unexpected connectionHow do rock layers record the history of ancient domes?Deformed rock layers reveal how circular parts of the Earth's surface were pushed upward into domes over time.

Sources

• [1]geological formation (Wikidata Q736917) · CC0 1.0
• [2]Geological formation · CC BY-SA 4.0
• [3]Hoodoo (geology) · CC BY-SA 4.0
• [4]List of rock formations · CC BY-SA 4.0
• [5]Dome (geology) · CC BY-SA 4.0