Investigation of the Neogene and Quaternary geology of the Milford and Mispillion River quadrangles has identified six formations: the Calvert, Choptank, and St. Marys formations of the Chesapeake Group, the Columbia Formation, and the Lynch Heights and Scotts Comers formations of the Delaware Bay Group. Stream, swamp, marsh, shoreline, and estuarine and bay deposits of Holocene age are also recognized. The Calvert, Choptank, and St. Marys formations were deposited in inner shelf marine environments during the early to late Miocene. The Columbia Formation is of fluvial origin and was deposited during the middle Pleistocene prior to the erosion and deposition associated with the formation of the Lynch Heights Formation. The Lynch Heights Formation is of fluvial and estuarine origin and is of middle Pleistocene age. The Scotts Corners Formation was deposited in tidal, nearshore, and estuarine environments and is of late Pleistocene age. The Scotts Corners Formation and the Lynch Heights Formation are each interpreted to have been deposited during more than one cycle of sea-level rise and fall. Latest Pleistocene and Holocene deposition has occurred over the last 11,000 years.

The hydraulic properties of the Piney Point (Eocene) aquifer and overlying basal silt of the Chesapeake Group (Miocene) were determined by a 23-day aquifer test conducted at the Danner Farm Well Field of the City of Dover, Delaware. During the test, head changes were monitored continuously in the Piney Point aquifer, overlying Cheswold (Miocene) aquifer, and the intervening confining bed.

Analyses of drillers' and geophysical logs, cuttings, and 29 core samples from well Nc13-3 near Greenwood, Sussex County, Delaware indicate that the 1500-foot section penetrated by the drill can be divided into seven rock-stratigraphic units: Matawan Formation, Monmouth Formation, unit A, Piney Point Formation, Chesapeake Group (undifferentiated), Staytonville unit, and the Columbia Formation. The rock units are identified on the basis of texture, mineralogy, color, and interpretation of electric and gamma-ray logs. The oldest rocks penetrated are Upper Cretaceous; Tertiary and Quaternary rocks were also encountered. Correlations of the units encountered in the Greenwood test well with subsurface formations in adjacent parts of the Coastal Plain are explored utilizing lithologies, ages, positions in the stratigraphic column, and geophysical characteristics as criteria. Major time boundaries (Cretaceous-Tertiary; Early-Late Paleocene; Paleocene-Eocene; and Eocene-Miocene) are established by a preliminary study of mainly planktonic foraminifera. The Miocene-Pleistocene boundary was determined on changes in lithology across the unconformable contact.

Geohydrology of the Milford, Delaware area.

Geohydrology of the Dover Aera, Delaware