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DGS Annual Report

DGS Annual Report of Programs and Activities.

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Site content related to keyword: "Yorklyn"

Outcrop Bb25-c: The Yorklyn Railroad Cut

Rock Outcrop Bb25-c: The Yorklyn Railroad Cut

Wissahickon gneisses and amphibolites are exposed in the railroad cut near Yorklyn. Here the rocks are unusual because the layering is accentuated by the presence of fault gouge between the layers. Fault gouge forms as movement along a fault in hard, brittle rocks crushes and grinds the rocks into a powder. Gouge was a term used by miners because they could easily "gouge" it out of the rock. Here the gouge "weathered out" leaving deep indentations that emphasize the layering and the tilt, which is to the southeast at an angle of about 45 degrees.

RI59 Bedrock Geology of the Piedmont of Delaware and Adjacent Pennsylvania

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.

B19 Geology and Hydrology of the Cockeysville Formation Northern New Castle County, Delaware

B19 Geology and Hydrology of the Cockeysville Formation Northern New Castle County, Delaware

The effect of rapid growth in the Hockessin and Pleasant Hill areas in northern Delaware has caused concern about possible declines in ground-water recharge to the underlying Cockeysville Formation. The Cockeysville is a major source of ground water (aquifer) in the Hockessin area from which about 1.5 million gallons of water per day is withdrawn for public water supply, even though it receives recharge over a relatively small area of 1.6 square miles. The Cockeysville in the Pleasant Hill area is currently used as a source at water supply for individual domestic users and one school. Results of ground-water exploration in the Pleasant Hill area suggest that the Cockeysville is capable of yielding several hundreds of gallons per minute to individual wells for water supply. A two-year investigation was undertaken to map the extent of the Cockeysville Formation and address questions of long-term ground-water yields. the sources of recharge, and the effects of additional development on ground-water supplies. Results of various field studies were integrated to determine the basic geologic framework and those elements that particularly affect ground-water supply.

What are GeoAdventures?

The Wilmington Western Railroad follows the Red Clay Valley through the Delaware Piedmont cutting through many of the Piedmont rock units.

GeoAdventures are designed to allow the reader to learn about a particular geologic point of interest in Delaware’s Piedmont province and then take a short field trip to that area. Want to know more about the Wilmington blue rock or Brandywine blue granite? Take the Wilmington Blue Rock GeoAdventure and go see just what the blue rock looks like.