For many years, there has been a question in the minds of some Delawareans as to whether Delaware's highest elevation is Centreville or on Ebright Road. The Delaware Geological Survey (DGS) at the University of Delaware, through its relationship to the National Geodetic Survey (NGS) has determined that the highest monumented spot in Delaware is located on Ebright Road, near the Pennsylvania state line. Ebright Road is north of Namaans Road, east of route 202.

Hurricane Sandy was a major storm event for the tidal areas of Delaware. As a part of the mission of the Delaware Geological Survey, we have compiled preliminary data related to Delaware tide and stream levels related to the Hurricane Sandy and compared them with previous flooding records.

Friday, October 19th has been designated Geologic Map Day 2012. As an extension of the National Cooperative Geologic Mapping Program of USGS, Geologic Map Day focuses the attention of students, teachers, and the general public on the study, uses, and significance of geologic maps for education, science, business, and a variety of public policy concerns.

The Delaware Geological Survey has released the Delaware Geologic Information Resource (DGIR), an online data display tool and map viewer for geologic and hydrologic information, as a "beta" site. DGIR was designed to provide the Delaware professional community with a variety of geoscience data in one application. DGS will continue to refine the both the data and functionality of the website as it is reviewed.

The Delaware Geologic Information Resource (DGIR) is an online data display tool and map viewer for a variety of geologic and hydrologic information released by the Delaware Geological Survey. It was designed to deliver the most commonly available and requested geologic and hydrologic information that is appropriate for use in hydrologic studies, required by regulation and ordinance, and to support state resource management decisions.

Gardeners from northern New Castle County should be grateful that the glaciers stopped their descent at the Delaware Water Gap about 100,000 years ago.

William "Sandy" Schenck lead a field trip through the Delaware Piedmont for the A.I. duPont High School Earth Science Class. The trip made use of the Wilmington-Western Railroad and everyone rode the railroad's "Doodle Bug." Activities included up close examinations of rock and mineral features and even "Panning for Garnets" at Brandywine Springs Park.

The Red Clay Creek has flowed through the rolling hills of northern Delaware for many thousands of years, cutting a deep valley into the old deformed rocks of the Appalachian Piedmont. The Red Clay valley contains many of the common rocks found throughout the Delaware Piedmont.

Published as a Special Publication, this is the first generalized statewide geologic map of Delaware.

The Tatnall Preschool Grounds contain many light-colored, coarse-grained, igneous-looking rocks (Barley Mill Gneiss) with mafic enclosures. These mafic enclosures make up only a small part of the rock. They may either be random in slope or they are elongated. When the Upper School and Preschool were built in the 1970s and 1980s, a lot of rock was removed from the foundations. The rock is either scattered around as large boulders in the landscaping, or in the back of the athletic fields in a large dump. The rocks in the dump show examples of mafic rock (greenish in color), part mafic and part pegmatite, and granitic rock.

Along the edge of the Red Clay Creek exists a large outcrop that extends out into the stream. This rock is part of the Wissahickon Formation, with pelitic facies, ½" elongated sillimanite nodules, and disharmonic folds. The compositional layering of this rock is 1/8 – ½" of biotite rich layers alternated with fine-grained psammitic layers (not quartz-feldspar layers). Some of these layers are sheared (shear zones). The sillimanite nodules, pegmatite pods, and shear zones in this rock are all parallel to fold axes. The axial plane of these folds is 20 degrees east of north, plunges 42 degrees northeast, and dips 90 degrees. Within this large outcrop are several 2-3' layers of “rock that rings” (when hit) and are folded with petitic gneiss. This pelitic gneiss shows more intense folding while the rest of the rock is gently folded. The “rock that rings” is also peppered with small lavender garnets.

Considered one of Delaware's most famous Piedmont outcrops, the Windy Hills Bridge outcrop is composed of mafic and felsic gneiss of the Windy Hills Gneiss. Much of the layering in the outcrop is regular and is 8 to 10" thick. At the contact between these layers there is evidence of partial melting. In terms of mineralogy, this rock contains mainly hornblende, plagioclase, quartz, biotite and epidote. This outcrop shows tight folds that plunge steeply 70-90 degrees to the northeast and southwest. The gneiss is cut by a long lens of pegmatite, which intruded after the folding and metamorphosing that yielded the gneiss.

There is also an interesting layer of cobble just above the bedrock in this area presumed to be the contact with the Coastal Plain sediments. These newer outcrops to the southwest display a 4-10" pelitic layer which becomes more extremely magmatic, with 1" leucosomes and ½" mafic selvages.

Overall, strikes of foliations of the mafic and felsic layering in these outcrops are 70-75 degrees east of north and the dips are a steep 80-85 degrees to the southeast, or almost vertical.

Just northwest of the confluence of Mill Creek and an unnamed tributary is an abandoned quarry. This quarry sits off the greenway trail, across from a ruined foundation wall, and displays samples of black, coarse-grained, foliated amphibolite. The unnamed tributary and Mill Creek are choked with amphibolite rocks and boulders. The amphibolite here weathers with a rusty rind and has a foliation strike of 10 degrees east of north and an obviously steep to vertical dip.

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.

In Claymont, DE, the intersection of Marvel Avenue and Parkside Boulevard occurs at Lesher Park, which contains Perkins Run, a creek West of Harvey Road. In the streambed of this creek is an outcrop of Perkins Run Gabbro, which is part of the Arden Plutonic Supersuite. The gabbro displays joints that are oriented 10 degrees west of north. Along these joints, veins of charnockite (orthopyroxene-bearing granite of the Ardentown Granitic Suite) can be found.

Located in Ardentown are a few silicic boulders just on the northwestern side of the railroad bridge that crosses the South Branch of Naaman Creek. These boulders are part of the Ardentown Granitic Suite. Some have very large (several cm) feldspar phenocrysts. Some display contacts between granitic rock and quartz-rich rock, which is probably metasedimentary rock due to the granular nature of quartz.

On the south side of Chestnut Hill is an outcrop of very large boulders in the woods of Hanby Park near Arden, DE. This area of the park seems to be the site of an old quarry. The rocks here are very similar to the rocks found down the South Branch of Naaman Creek (Ardentown and Ardencroft) as they both share the same fine-grained, mafic properties with traces of coarse-grained charnockite.