This vector data set contains the rock unit polygons for the surficial geology in the Delaware Coastal Plain covered by DGS Geologic Map No. 16 (Fairmount and Rehoboth Beach quadrangles). The geologic history of the surficial units of the Fairmount and Rehoboth Beach quadrangles is that of deposition of the Beaverdam Formation and its subsequent modification by erosion and deposition related to sea-level fluctuations during the Pleistocene. The geology reflects this complex history both onshore, in Rehoboth Bay, and offshore. Erosion during the late Pleistocene sea-level low stand and ongoing deposition offshore and in Rehoboth Bay during the Holocene rise in sea level represent the last of several cycles of erosion and deposition.
To facilitate the GIS community of Delaware and to release the geologic map of the Fairmount and Rehoboth Beach quadrangles with all cartographic elements (including geologic symbology, text, etc.) in a form usable in a GIS, we have released this digital coverage of DGS Geological Map 16. The update of earlier work and mapping of new units is important not only to geologists, but also to hydrologists who wish to understand the distribution of water resources, to engineers who need bedrock information during construction of roads and buildings, to government officials and agencies who are planning for residential and commercial growth, and to citizens who are curious about the bedrock under their homes. Formal names are assigned to all rock units according to the guidelines of the 1983 North American Stratigraphic Code (NACSN, 1983).
In Delaware some linear features recognized on the Landsat image can be related to known faults. Others are interpreted as possible faults; the causes of some lineations are not yet known. Circular features are more difficult to interpret but they are similar to the domal structures and erosional features recognized in the Gulf Coast region, for example. These and the linear features of uncertain origin can be investigated by drilling and geophysical techniques after being localized by clues provided by the satellite images. Detection by satellite images and confirmation by other geologic techniques is an efficient and effective means of geologic investigation.
On October 21, 1878, a hurricane crossed the island of Cuba and headed east of Key West, Florida. On the evening of October 22, it made landfall north of Cape Lookout, North Carolina, as a low Category 2 hurricane with winds around 100 mph. The storm picked up speed after landfall and moved northward at a rate of greater than 40 mph and maintained tropical storm force wind speeds of greater than 60 mph with gusts much higher. On the morning of October 23, it passed up the west side of the Chesapeake Bay near the cities of Baltimore and Annapolis, Maryland, Wilmington, Delaware, and Philadelphia, Pennsylvania. By the late afternoon it had reached Albany, New York, and turned eastward and passed out to sea north of Boston, Massachusetts, on the morning of October 24.