Iron Hill Gabbro

OFR54 Bedrock Geologic Map of the Delaware Piedmont

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:

OFR55 Delaware Geological Survey Petrographic Data Viewer

Petrography is a branch of geoscience focused on the description and classification of rocks, primarily by microscopic study of optical properties of minerals. A thin sliver of rock is cut from a sample, mounted on a glass slide, ground to approximately 30 microns (0.03mm), and viewed under a microscope that uses polarized light. By observing the colors produced as plain polarized light and crossed (90 degrees) polarized light shines through the minerals, petrologists can determine the minerals that comprise the sampled rock.

Outcrop Da15-h: The Paraglacial Boulder Feature of Chestnut Hill

Prime examples of Iron Hill Gabbro can be found in the area surrounding Chestnut Hill at Rittenhouse Park. The gabbro here is considered coarse to very coarse grained. Boulders of Iron Hill Gabbro are located on the northeast facing slope southwest of the Christina Creek. This gabbro boulder field is probably a paraglacial feature left over from ice age times deep in Delaware’s geologic past.

This page tagged with:
Iron Hill Gabbro
outcrop
Appalachian Piedmont
Chestnut Hill

RI59 Bedrock Geology of the Piedmont of Delaware and Adjacent Pennsylvania

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.

GM13 Geologic Map of New Castle County, Delaware

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.