body of rock identified by lithic characteristics and stratigraphic position; it is usually but not necessarily tabular and is mappable at the Earth's surface or traceable in the subsurface. Smaller than a subgroup
Figure 1. A geologic cross section of the Grand Canyon.
A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exposed in a geographical region (the stratigraphic column). It is the fundamental unit of lithostratigraphy, the study of strata or rock layers.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).