The Piedmont rock units in Delaware, and bedrock geologic map of Schenck et al. (2000) are revised in this report based on new rock geochemistry, geochronometric data, petrography, and recent detailed mapping. Major revisions include:
The Art in Science exhibit will be held from April 4 to April 16 in the University of Delaware Harker Lab. With a two week display of art culminating in a symposium on the 16th, Art in Science is geared toward highlighting cutting edge research at UD across all disciplines in order to educate and engage the local community and to spark interest in STEM activities in underrepresented student populations.
Found in the creek bed and flood plain, the large boulders in Shellpot Creek are excellent examples of Bringhurst Gabbro. The gabbro is very coarse-grained with crystals up to 2" long; however, variations in the grain size exist over a scale of a few inches. While observing this rock closely, one can occasionally find grains of orthopyroxene (possibly bronzite) up to 4" long. Some of the boulders have grains of olivine surrounded by double coronas of orthopyroxene, spinel, and hornblende.
This report accompanies a new map that revises the original bedrock geologic maps of the Delaware Piedmont compiled by Woodruff and Thompson and published by the Delaware Geological Survey (DGS) in 1972 and 1975. Combined detailed mapping, petrography, geochemistry, and U-Pb geochronology have allowed us to redefine two rock units and formally recognize eleven new units. A section of the Pennsylvania Piedmont is included on the new map to show the entire extent of the Mill Creek Nappe and the Arden Plutonic Supersuite.
Coarse- to very coarse-grained gabbronoite with subophitic textures. Primary minerals are plagioclase, olivine, clinopyroxene and orthopyroxene. Olivine, where present, is surrounded by an inner corona of orthopyroxene and an outer corona of pargasitic hornblende, both with spinel symplectites. The gabbronorites locally contain abundant xenoliths of mafic Brandywine Blue Gneiss.
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.
Crystalline bedrock geology of the Wilmington area, Delaware.