ABSTRACT
The geological framework is the key to any groundwater investigation. It follows that geologic mapping, of both the surface and subsurface (cross-sections), is one of the ˜rst ˜eld phases of an investigation. In most areas of the United States, some geologic mapping has been done and serves as a basis for that required in a groundwater study. Particular attention is given to the geologic units that will most affect the occurrence, movement, and quality of groundwater.
