Since 1992, the Delaware Geological Survey (DGS) has compiled a geologic database known as the Delaware Offshore Geologic Inventory (DOGI) that consists of sediment samples, radiocarbon and amino acid racemization dates, seismic profiles, and vibracores taken from the nearshore and inner continental shelf in state and federal waters. Most of the 366 vibracores are stored at the DGS on-site core and sample repository.
The DGS has worked in partnership with the US Minerals Management Service (MMS) and the Delaware Department of Natural Resources and Environmental Control (DNREC) to determine the distribution, texture and location of sand bodies and how they relate to the stratigraphic framework. As of 2010, more than 77 million cubic yards of beach-quality sand that can be used for future beach fill along Delaware’s Atlantic shoreline have been identified.
Any sediments obtained from areas containing beach-quality sand are expected to be consistent with the recommendations presented by Ramsey (1999). Textural characteristics were determined from sampling the beach and nearshore and represent the “native composite” for size and sorting that are stable under average wave and current activity.
Although there are some textural differences along the Atlantic beaches, placement of nourished sand material should be in the coarse sand or the coarse half of the medium sand range. The sediment should be well to very well sorted and skewed toward an excess of coarse material.
The following tables provide the definitions of lithologic and resource rating symbols.
|Gravel (G)||(> 2.00 mm or -1.0 to -6.0 phi)
with 0 to 20% silt or sand
|Sand (S)||(2.0 to -1.0 phi)
medium to very coars with 0 to 10% silt or gravel
|Fine or Silty Sand (L)||(4.0 to 2.0 phi)
very fine to fine with 0 to 35% silt
|Mud (M)||(> 4.0 phi)
coarse silt and finer material
|gS||5 to 30% gravel in sand matrix|
|Excellent (E)||Cores with sediments at top: >10S; 5S followed by 5gS; <5s followed by 10gS; 5gS followed by 5S; 2gS followed by 10S|
|Good (G)||Cores with sediments at top: between 10S and 5S; 5gS followed by 5S; 5gS; 5I followed by 5S|
|Fair (F)||Cores with sediments at top; between 2s and 5s, I, or g; 5gS followed by I or m; <2m followed by 10S or 10L; <2s followed by >5L|
|Poor (P)||Cores with sediments at top; <2 feet thick; <2s followed by > 5M; <5L followed by 10M|
The map (linked below) shows the locations of all of the cores in the DOGI database and assigned a lithologic character (gravel, gravelly sand, sand, fine and silty sand, and mud. From that, a color-coded resource rating of Excellent (green); Good (yellow); Fair (blue); and Poor (brown) were assigned for the core’s suitability as beach fill. This resource rating is an indication of the compatibility of the sediment contained in the core with the native composite.
To find more information about a particular core, click on its location and a balloon will provide the latitude and longitude, water depth, core length, detailed lithologic rating and for most, the lithologic description, photos, and depositional history.