Outcrops between Hidden Valley Drive and Farmhouse Road. The Christianstead subdivision is underlain by interlayered mafic and felsic gneiss with large pegmatites. The felsic gneiss, in the northwestern half of this subdivision, is deformed granodiorite, seen as massive igneous layers with only rare crinkle folding. There are a few “bright eye” textures on the west end of this subdivision, which is all underlain by granodiorite.
Coarse-grained, foliated granodioritic gneiss. Major minerals are biotite, microcline, plagioclase, and quartz. Includes thin layers of fine-grained foliated amphibolite plus large pegmatites.
All the rock units in Delaware’s Piedmont are highly deformed. Deformational features, such as folds, faults, and/or joints, are present in almost every outcrop.
This map shows the surficial geology of New Castle County, Delaware at a scale of 1:100,000. Maps at this scale are useful for viewing the general geologic framework on a county-wide basis, determining the geology of watersheds, and recognizing the relationship of geology to regional or county-wide environmental or land-use issues. This map, when combined with the subsurface geologic information, provides a basis for locating water supplies, mapping ground-water recharge areas, and protecting ground and surface water.
This is a map of the crystalline bedrock units in the Piedmont of Delaware and adjacent Pennsylvania. The southern boundary of the mapped area is the updip limit of the Potomac Formation (Woodruff and Thompson, 1972, 1975). Soil, regolith, and surficial deposits of Quaternary age are not shown.