What type of rock unit can a formation be classified as?

A formation is a fundamental unit of geologic mapping, and it can be classified not just by one type of rock but rather as a distinguishable body of rock with specific characteristics and boundaries. This classification allows geologists to identify and describe formations based on their lithology, composition, and other features that make them distinct within an area. Formations can be composed of various rock types, including igneous, sedimentary, and metamorphic rocks, or a combination thereof.

The key aspect of a formation is its ability to be recognized and differentiated from other rock units based on these characteristics, making the option of being distinguishable by type and boundaries accurate and comprehensive. This concept is crucial for geological mapping and understanding the geological history of a region, as it facilitates correlation and provides insights into the processes that formed the rocks.