Delaware Geological Survey releases new geologic map of offshore Delaware

The Delaware Geological Survey (DGS) has published a geologic map of the state’s offshore geology, entitled Geologic Map of Offshore Delaware. Geologic Map 25 presents the results of research by DGS scientists C. Robin Mattheus, Kelvin W. Ramsey, and Jaime L. Tomlinson. The map shows the detailed seafloor geology across State and Federal waters of Delaware’s inner continental shelf.

Geologic Map 25 was constructed by a thorough analysis of over 450 offshore vibracores and approximately 300 miles of high-resolution subsurface seismic reflection data. The latter was used to help establish lateral continuity of geologic units and delineate lithologic boundaries at the sediment-water interface, in conjunction with bathymetric datasets. The map contains detailed descriptions of all units, including age assignments based on radiocarbon dates and estimates from amino acid racemization analysis. A series of geologic cross sections illustrates how surface morphology relates to underlying units and structures, including paleovalleys. The geologic information contained within this map is useful for offshore sand and gravel resource assessment. It also has implications for offshore infrastructure projects, such as windfarm and submarine-cable placement, and improves our understanding of modern shelf-sediment dynamics. The map is part of the Delaware Geological Survey’s ongoing mission to understand geologic systems and to advise, inform, and educate Delawareans about the results of such investigations.

DGS Geologic Map No. 25 is available as a PDF, which can be viewed online, or downloaded for print on demand from the DGS web page at

For questions and information, contact DGS at, 302-831-2833