Iron Hill Gabbro

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.

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.