District of Columbia (Washington D.C.), USA
|Location is approximate, based on center of defined region.|
|Latitude & Longitude (WGS84):||38° 52' 60'' North , 77° 1' 0'' West|
|Latitude & Longitude (decimal):||38.88333,-77.01667|
|Museums in region:|
Washington D. C. is a 100 square mile area set aside to serve as the Capital of the United States of America. It is situated near the "Fall Line" separating the Piedmont Province's older rocks, deformed during the Taconic Orogeny, from the Cretaceous and Tertiary rocks of the Coastal Plain. That line is marked by a chain of rapids and falls as rivers, such as the Potomac, move from resistant metamorphic and igneous rocks to softer, less consolidated sedimentary rocks. Most of the city is built on the marshy terrain of the Coastal Plain. Piedmont Province rocks are widely exposed in Rock Creek Park and at Great Falls, a few miles northwest of the District's limits. Coastal plain rocks can be seen at Fort Totten Park and other spots in the eastern part of the city. Outcrops in the District are otherwise sparse. Most of the reported minerals are from ephemeral construction sites and road cuts. However a great variety of building stones are on display in the many government buildings and monuments. Some of the world's best mineral and geology displays are in the Natural History Museum of the Smithsonian Institute.
Mineral ListMineral list contains entries from the region specified including sub-localities
26 valid minerals.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
0 - 2.588 Ma
|Maryland Point Formation|
Age: Pleistocene (0 - 2.588 Ma)
Stratigraphic Name: Maryland Point Formation
Description: Mainly fine- to coarse-grained sand, well-sorted to poorly sorted, tan to orange in the upper third; poorly sorted silty gray to olive clay in most of the lower two-thirds, and olive gray pebbly sand at the base. The clay contains plant fragments in places. Oyster beds with sandy mud matrix are present at 1 to 3 m (3 to 10 ft) above sea level in bluffs east and west of Maryland Point, south of the Washington West quadrangle on the north side of the Potomac River in western Charles County, Md. Sediment is mainly derived from older Coastal Plain deposits nearby. A single 14C age of wood chips from a Maryland Point Formation clay bed at the mouth of Chicamuxen Creek is 20,500+/-500 years (Meyer Rubin, USGS, written communication, 1986). The unit is typically 1.5 to 14 m (5 to 40 ft) thick; the top of the unit is about 6 to 9 m (20 to 30 ft) above sea level. In most places, the upper surface of the Maryland Point Formation is approximately the present land surface and the lower contact rests unconformably on Miocene and older units. The Maryland Point Formation as described here includes both the Maryland Point Formation and the Kent Island Formation of the Charles County, Md., and St. Marys County, Md., maps (McCartan, 1989 b, c). This unit is equivalent to Qts in Virginia
Lithology: Sandy gravel
Reference: Davis, A.M., C.S. Southworth, J.E. Reddy, J.S. Schindler. Geologic Map Database of the Washington DC Area Featuring Data from Three 30 x 60 Minute Quadrangles: Frederick, Washington West, and Fredericksburg. U.S. Geological Survey Open-File Report 01-227. 
0.0117 - 2.588 Ma
Age: Pleistocene (0.0117 - 2.588 Ma)
Description: Gravel, sand, silt, and clay. Medium- to coarse-grained sand and gravel; cobbles and boulders near base; commonly contains reworked Eocene glauconite; varicolored silts and clays; brown to dark gray lignitic silty clay; contains estuarine to marine fauna in some areas (includes in part Pamlico, Talbot, Wicomico and Sunderland Formations of earlier reports); thickness 0 to 150 feet.
Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052.