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Aerial photograph southwest of Blackbird, Delaware, showing the Borthwick area
Description
Overlay map of the topography showing the basins and rims. Scale 1, 4,800, Contour Interval 2 Feet. Datum is Mean Sea Level.; From Rasmussen, W., Geology and Hydrology of the Bays and Basins of Delaware, 1958 , Plate 4A.
