Is shale regional or contact

Shale is typically considered a regional rock type, as it forms from the accumulation of fine-grained sediments over large areas in a variety of environments, such as river deltas, floodplains, and deep marine settings. It can extend over significant distances and is often associated with sedimentary basins. While contact metamorphism can occur in localized areas where shale is intruded by hot magma, the primary characteristics and formation processes of shale are best described on a regional scale.