Mapping was conducted using field maps at a scale of 1:12,000 with 2-ft contours. Stratigraphic boundaries drawn at topographic breaks reflect detailed mapping using contours not shown on this map. Most stratigraphic units mapped in stream valleys are projected from subsurface data. Except for a few erosional bluffs, these units are covered by colluvium. This map supersedes Geology of the Middletown-Odessa Area, Delaware: Delaware Geological Survey Geologic Map Series No. 2 (Pickett and Spoljaric, 1971).
In 2015, staff of the Water Supply Section of the Delaware Department of Natural Resources and Environmental Control (DNREC) informed the DGS of their concerns about overpumping of the unconfined Columbia aquifer in an area east of Dover (Figure 1). In this area, the City of Dover’s Long Point Road Wellfield (LPRW) and numerous irrigation systems pump water from the shallow Columbia aquifer.
The geological history of the surficial units of the Clayton, Smyrna, and the Delaware portion of the Millington Quadrangles are the result of deposition of the Beaverdam Formation and its modification by erosion and deposition of the Columbia Formation during the early Pleistocene. These units were then modified by the Lynch Heights and Scotts Corners Formations as a result of sea-level fluctuations during the middle to late Pleistocene. The geology is further complicated by periglacial activity that produced Carolina Bay deposits in the map area, which modified the land surface.
The following table displays the correlation of hydrologic units to geologic units recognized by the Delaware Geological Survey in the Atlantic Coastal Plain.
Consists of 30 ft of silty, shelly, fine sands that are commonly glauconitic (Benson and Spoljaric, 1996). Deposited during the latest Paleocene to early Eocene (Benson and Spoljaric, 1996). Based on microfossils (unpublished DGS file data), it can be characterized as an open shelf deposit.
The Bethany Beach borehole (Qj32-27) provides a nearly continuous record of the Oligocene to Pleistocene formations of eastern Sussex County, Delaware. This 1470-ft-deep, continuously cored hole penetrated Oligocene, Miocene, and Pleistocene stratigraphic units that contain important water-bearing intervals. The resulting detailed data on lithology, ages, and environments make this site an important reference section for the subsurface geology of the region.
If you think you may have found a Delaware dinosaur or any unusual fossil, the scientists at the Delaware Geological Survey at the University of Delaware, Newark campus would like to see it. It could provide important information on the geologic history of the First State.
This Bulletin presents the subsurface stratigraphy of the post-Potomac Cretaceous and Tertiary rocks of the Atlantic Coastal Plain of central Delaware, between the Chesapeake and Delaware (C & D) Canal and Dover. Geophysical log correlations supported by biostratigraphic and lithologic data from boreholes in Delaware and nearby New Jersey provide the basis for the report.