The Columbia sediments of Delaware cover almost all of the surface of the Coastal Plain portion of the State. A major unconformity separates these predominantly sandy materials from the underlying rocks of the Coastal Plain. As it includes the materials closest to the surface in most places, the Columbia has great practical importance in Delaware. In addition to the morphology and soils which are largely dictated by the Columbia, it holds about 90 percent of the State's groundwater supplies, is the geologic foundation for most construction, and yields essentially all of the sand and gravel mined here.
Please give proper credit to the Delaware Geological Survey.
Delaware Geological Survey
University of Delaware
Delaware Geological Survey Building
Newark, DE 19716
Mon - Fri; 8:00am to 4:30pm