The Wellington Formation is an Early Permian geologic unit in Kansas and Oklahoma that extends into the northeastern Texas Panhandle. Long known for its soft dark shale, it records mostly non-marine settings such as freshwater ponds, salt lakes, and exposed soils, with only limited marine beds at the bottom. Its Hutchinson Salt Member remains an important mined resource in central Kansas, but near-surface salt dissolution also causes subsidence, altered streams and wetlands, and sinkhole hazards. The formation is also a major scientific archive, preserving climate cycles, seasonal layering, and abundant fossils, including insects, reptiles, and Meganeuropsis permianum, the largest known winged insect.