lithologies

Lithology is the science concerned with describing the physical characteristics and composition of rocks. It emphasizes macroscopic properties such as rock type, mineral content, texture, grain size, color, porosity, cementation, and hardness. Lithology provides a practical framework for describing and mapping rocks in the field and in subsurface databases. It is distinct from petrography, which focuses on microscopic textures and mineralogy, and from pure mineralogy, which centers on mineral species.

In geology, lithology underpins lithostratigraphy, the branch that defines and correlates rock units primarily by their lithologic characteristics rather than age. Descriptions of a rock sequence often rely on identifying predominant lithologies (for example, sandstone, mudstone, limestone) and any transitions or interbedded lithologies that record changes in provenance, sediment supply, or diagenetic history. Lithologic information can reveal depositional environments, diagenetic processes, weathering intensity, and tectonic influences.

Common lithologies include siliciclastic rocks such as sandstone, siltstone, and shale; carbonate rocks like limestone and dolostone; chemical or evaporite rocks such as gypsum, anhydrite, and halite; and igneous or metamorphic rocks when appropriate to the region. Complex sequences may contain multiple lithologies, requiring detailed stratigraphic logs and cross-sections for accurate interpretation.

Beyond Earth, lithology is used in planetary geology to describe rock types on other planets and moons, aiding the interpretation of remote-sensed data and guiding exploration.