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Site content related to keyword: "Appalachian Piedmont"

OneGeology

DGS participates in OneGeology initiative
Project Contact(s):

OneGeology (http://www.onegeology.org/) is an international effort to make available digital geologic map data from around the world. DGS participates in OneGeology by submitting two web map services, one for 1:100K scale surficial geologic units and one for 1:100K scale surficial geologic contacts. These services are open and interoperable (supporting both WMS and WFS protocols) with data attributes in GeoSciML-Portrayal format.

Highest point in Delaware

Ebright Azimuth - The Highest Monumented Point in Delaware

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.

Stream and Tide Gage Data for Hurricane Sandy

GOES Satellite Image of Hurricane Sandy (Image provided by NASA)

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.

Celebrate Geologic Map Day 2012!

DGS Geologic Map 16

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.

DGS releases new DGIR web application

Delaware Geologic Information Resource (DGIR) Web Application

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.

Delaware Geologic Information Resource (DGIR) Map Viewer

DGIR Map Viewer Screenshot
Project Contact(s):

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.

Gaining new appreciation of rocks in the garden

Stone walls near Brandywine Creek State Park are built of native fieldstone, including amphibolites and Brandywine granite, or gneiss, which gave the Wilmington Blue Rocks baseball team its name. / News Journal file/ROBERT CRAIG

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.

Common Rocks and Minerals of the Delaware Piedmont

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.

Biotite Tonalite

Sbt

Fine- to medium-grained, equigranular biotite tonalite usually occurring as rounded boulders. Tonalites are leucocratic (15 to 25% modal mafic minerals), light gray to buff on fresh surfaces, and locally contain mafic enclaves with reddish rims, the result of iron hydroxide staining. Possibly intrusive into the Perkins Run Gabbronorite Suite.

Geochemical Data of Mafic Rocks in Delaware Piedmont, PA and MD

Geochemical Data of Mafic Rocks in Delaware Piedmont, PA and MD

Geochemical data from Ordovician and Silurian mafic rocks in the Wilmington Complex in Delaware, the James Run Formation in Cecil County, Maryland, and the Wissahickon Formation in Delaware and Pennsylvania were collected in conjunction with preparation of a new geologic map of the Delaware-Pennsylvania Piedmont. Although concentrations of most elements may have been disrupted by metamorphism, the more stable high field strength elements, including the rare earth elements (REE), are consistent within mapped lithodemic units and are compared to modern basaltic magmas from relatively well known tectonomagmatic environments.

Our results are similar to those for other Appalachian mafic rocks and suggest a suprasubduction zone tectonic setting for the Wilmington Complex and the James Run Formation in Cecil County, Maryland. Thus, the rocks of the Wilmington Complex plus the James Run Formation in Cecil County may be stages in a continuum that records the temporal magmatic evolution of an arc complex.

Delaware Geological Survey Radiocarbon Database

Delaware Geological Survey Radiocarbon Database

Radiocarbon dates from 231 geologic samples from the offshore, coastal, and upland regions of Delaware have been compiled along with their corresponding locations and other supporting data. These data now form the Delaware Geological Survey Radiocarbon Database. The dates range from a few hundred years to approximately 40,000 yrs (40 ka) BP (before present). All dates younger than about 18,000 yrs have been calibrated using the method of Stuiver and Reimer (1993). A plot of the dates versus the elevations of the samples shows four distinct groupings: those associated with the rise of sea level during the Holocene, those from the uplands, those in modem stream valleys, and those older than the detectable range of present radiocarbon techniques. A fifth group of samples in the 20-38 ka range and from below present sea level are ambiguous and were previously used as evidence for a mid-Wisconsinan high sea stand (Milliman and Emery, 1968).

Outcrop Bc44-f: The Tatnall Preschool Grounds

Rock Outcrop Bc44-f: The Tatnall Preschool Grounds

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.

Outcrop Cc12-c: The Red Clay Creek Edge

Rock Outcrop Cc12-c: The Red Clay Creek Edge

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.

Outcrop Cb42-c: Windy Hills Bridge Outcrop

Rock Outcrop Cb42-c: The Windy Hills Bridge Outcrop

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.

Outcrop Cb15-c: The Confluence Quarry at North Pointe

Rock Outcrop Cb15-c: The Confluence Quarry at North Pointe

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.

Outcrop Ca44-d2: The Christianstead Subdivision

Rock Outcrop Ca44-d2: The Christianstead Subdivision

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.

Outcrop Be32-g: Lesher Park Streambed

Rock Outcrop Be32-g: Lesher Park Streambed

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.

Outcrop Be22-e: Ardentown Railside Boulders

Rock Outcrop Be22-e: Ardentown Railside Boulders

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