20220225 11174900 FALSE 20100511 08223400 20100511 08223400 1.0 ESRI ArcCatalog 9.3.1.3000 en REQUIRED: A brief narrative summary of the data set. Geologic formations. Surface geology. REQUIRED: The name of an organization or individual that developed the data set. REQUIRED: The date when the data set is published or otherwise made available for release. Geology (Polygons) Geology_poly vector digital data withheld REQUIRED: The basis on which the time period of content information is determined. 10/16/2006 REQUIRED: The state of the data set. When Needed -77.192768 -77.030238 38.946790 38.812384 11855380.620000 11900924.090000 6982243.700000 7030511.230000 REQUIRED: Reference to a formally registered thesaurus or a similar authoritative source of theme keywords. REQUIRED: Common-use word or phrase used to describe the subject of the data set. REQUIRED: Restrictions and legal prerequisites for accessing the data set. 1:24,000 Feature Class Bill Grether GIS Mapping Center Bureau Cartographer II
2100 Clarendon Blvd Ste 813
Arlington VA 22201 gismc@arlingtonva.us withheld Sample Image 1 JPEG ESRI ArcCatalog 9.3.1.3000 Geology_poly 11855380.62 11900924.09 7030511.23 6982243.7 1 -77.192768 -77.030238 38.94679 38.812384 1 en FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998 local time REQUIRED: The person responsible for the metadata information. REQUIRED: The organization responsible for the metadata information. REQUIRED: The mailing and/or physical address for the organization or individual. REQUIRED: The city of the address. REQUIRED: The state or province of the address. REQUIRED: The ZIP or other postal code of the address. REQUIRED: The telephone number by which individuals can speak to the organization or individual. 20100511 http://www.esri.com/metadata/esriprof80.html ESRI Metadata Profile ISO 19115 Geographic Information - Metadata DIS_ESRI1.0 dataset Downloadable Data 002 withheld Local Area Network Feature Class Vector Simple Polygon TRUE 259 TRUE FALSE 2 1 5.000000 FALSE 81 82 83 84 G-polygon 259 GCS_North_American_1983 NAD_1983_StatePlane_Virginia_North_FIPS_4501_Feet coordinate pair survey feet 0.000625 0.000625 Lambert Conformal Conic 38.033333 39.200000 -78.500000 37.666667 11482916.666667 6561666.666667 North American Datum of 1983 Geodetic Reference System 80 6378137.000000 298.257222 Explicit elevation coordinate included with horizontal coordinates 1.000000 NAD_1983_StatePlane_Virginia_North_FIPS_4501_Feet 259 Geology_poly Feature Class 259 OBJECTID OBJECTID OID 4 10 0 Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. UNIT UNIT String 8 0 0 Geologic Unit (See geology look up table for values) af Artificial Fill -- Heterogeneous materials found in large areas regraded, leveled, or filled for construction. Also includes fill of marshes or low-lying areas and those formerly mined for sand, gravel, or clay. Smaller scale fills of variable composition and thickness found throughout the urbanized area have not been mapped. Qcl Colluvium (Quaternary) -- Unsorted mixture of rock fragments, gravel, sand, silt, and clay formed by slow creep or mass wasting downhill. Generally found on steep slopes underlain by Potomac Formation clays. Thickness varies from a few feet up to 30 feet, with the thickest deposits found at the toe of slopes. Qal Alluvium (Holocene) -- Unconsolidated sand, silt, gravel and clay fluvial deposits underlying modern floodplains and marshes. Sediments are moderately to crudely bedded, well to poorly sorted, of variable thickness. In the Piedmont, Qal consists of micaceous silt and sands, quartz and crystalline rock pebbles, cobbles, and boulders. Where streams drain the Coastal Plain, sediment is derived from weathered saprolite and older alluvial deposits and contains mostly well-rounded pebbles and cobbles, quartz sand and silt, and clays. Qts Stream Terrace Deposits (Holocene and Pleistocene) -- Gravel, sand, silt, and clay deposited in lowland benches 10 to 25 ft (3 to 8 m) above modern floodplains. Deposits are usually well-sorted, well-bedded material ranging in size from clay to cobbles. Qt2 Terrace Deposits (middle Pleistocene) -- Gravel, sand, silt, and clay , gray brown to medium orange, crudely to well bedded. Found in a terrace below a 50 ft (15 m) elevation west of the Potomac River. Minerology similar to Qal but more deeply weathered. Where unstripped, the upper few feet is yellow to medium orange due to accumulation of iron oxide. Thickness may be up to 35 feet (10 m). Qt1 Terrace Deposits (middle Pleistocene) -- Gravel, sand, silt, and clay, gray to gray-brown, crudely to well bedded. Found in an irregular terrace between 40 and 105 ft (12 m to 22 m) elevation. Similar to Qt2 but more deeply weathered so that relatively fresh minerals have been exposed. Typically 35 to 65 ft (10 to 20 m) thick. Tt5 Terrace Deposits (late Pliocene) -- Gravel, sand, silt, and clay, brownish-gray; medium orange in upper part. Rounded pebbles and cobbles and coarse-grained sands are poorly to well sorted and crudely bedded. Gravel consists of crystalline rocks, quartz, quartzite, and sandstone. Silt and clay are interstitial, probably emplaced post depositionally by infiltrating water. Clay is mainly kaolinite and soil vermiculite. Tt5 is recognized by firm pebbles and cobbles and by the thin weathered zone in unstripped sections. Found in terraces at elevations from 100 to 140 ft (30 to 40 m). Tt4 Terrace Deposits (late Pliocene) -- Crudely bedded gravel, sand, silt, and clay, pale-brown to medium yellow, reddish-orange in upper part. Gravel and sand are coarse, silt and clay are interstitial and emplaced post-depositionally. Materials are similar to Tt5 but more weathered. Some gravel clasts have desilicified and are friable. Tt4 is recognized by a few such clasts and thick brightly colored weathering profiles. Found in terraces between 170 and 190 ft (50 to 60 m). Tt3 Terrace Deposits (late Miocene) -- Gravel, sand, silt, and clay, reddish-orange to pale-gray in uper part, pale- to medium- yellow below. Unit is crudely bedded. Coarse gravel and sand; silt and clay are mainly post-depositional, although some is derived in place. Materials are similar to Tt5 and Tt4. Most of the crystalline and some quartzite clasts have weathered to clay or a loose aggregate of mineral grains. Tt3 is distinguished by thorough weathering and bright colors in the upper part of unstripped sections. Found as a terrace between 220 and 250 ft (65 to 75 m), overlaps wedge edge of Potomac Formation. Tt2 Terrace Deposits (Pliocene(?) and late Miocene(?)) -- Gravel, sand, silt, and clay, bleached white in upper part, to pale orange below; crudely bedded. Materials similar to Tt3. Weathering and leaching have removed much of the iron, accounting for the pale colors. Weathering has also disintegrated many of the gravel clasts. Tt2 is distinguished primarily by its color and position at elevation of about 360 to 410 ft 135 to 160 m). Tt1 Terrace Deposits (late Miocene(?)) -- Gravel, sand, silt, and clay, gray- to reddish-brown, found primarily at Tyson's Corner; the oldest and highest of the terrace gravels. Cross-bedded cobble and pebble gravel, consisting of well-rounded crystalline rocks in a matrix of sandy, reddish-brown clay and silt. Gravel clasts are deeply weathered and readily disintegrate. Fluvial gravel unit overlies lenticular sequence of light gray sand and weathered silty clay beds. Thin, unweathered conglomerate lenses occur at the base of the silty clay above unconforming Piedmont saprolite. A silicified log has been excavated from these stream channel deposits. Unit may be as much as 70 ft (21 m) thick and occurs at elevations between 450 and 520 ft (135 to 160 m). Kpu Potomac Formation, undivided (Early Cretaceous) -Varicolored clay and silt interbedded with pebbly to cobbly sand in fairly well bedded, interfingering fluvial deposits. Unit forms a southeastward-thickening prism of sediment up to 600 ft (180 m) thick. Unconformably overlies saprolite on Piedmont crystalline rocks. Kpc Potomac Formation, clay and silt (Early Cretaceous) -Red brown, green, and gray silty clay with minor lenticular sands. Clay has high shrink-swell characteristics due to predominance of montmorillonite, and is unstable on steep to moderate slopes. Probably derived from fluvial overbank deposits. Thickness is irregular. Kps Potomac Formation, sand and gravel (Early Cretaceous) --Buff to gray, find- to coarse-grained feldspathic quartz sand, interbedded with lenticular silt and clay. Thick-bedded units are commonly coarse-grained andcross-bedded. Unit fills erosional channels and grades to fine-grained silty sand probably of point-bar origin, then to overbank silts and clays (Kpc). Thickness is irregular. Oc Clarendon Granite (Early Ordovician) -- Leucocratic, moderate- to well-foliated, medium grained, biotite-muscovite monzo- granite. OCq Quartz Bodies (Ordovician and Cambrian) - Lenticular bodies or irregular masses of quartz. Some are foliated or polyfoliated, whereas other bodies are massive. Odt Muscovite trondhjemite -- Fine- to medium-grained, sugary textured, massive to weakly foliated. Forms dikes, sheets, and irregular bodies in monzogranite and adjacent country rocks. Oft Medium- to coarse-grained, medium-dark-gray biotite- hornblende tonalite, and biotite tonalite that typically contains abundant inclusions of mafic and ultramafic rocks. Rock is typically well foliated and in many places has a strong quartz-rod lineation. Oftr Medium-grained, light-pink to light gray, massive-appearing muscovite trondhjemite. It is strongly deformed and recrystallized. Ogh Medium- to coarse-grained, mafic biotite-hornblende tonalite that at many places is choked with xenoliths and/or autoliths of ultramafic, mafic, and metasedimentary rocks. Has a metamorphic foliation and quartz rod lineation as well as a relict flow foliation and lineation. Typically contains thin layers of biotite tonalite. Cs Light- to medium-gray, medium-grained sedimentary mélange consisting of a quartzofeldspathic matrix that contains quartz "eyes" and fragments of phyllonite, metagraywacke, migmatite, serpentinite, amphibolite, and actinic schist. Unit also contains mappable olistoliths of metagabbro (CZg), phyllonite (CZmp), migmatite (CZmm), and actinolite schist (CZu) Cso Upper part of unit, similar to main formation, but containing 50 percent or more phyllonite ostoliths. CZg Metagabbro (Cambrian or Late Proterozoic) Dark green, well-foliated medium- to coarse-grained gabbro and much lesser serpentinized peridotite and plagiogranite. CZu Actinolite Schist (Cambrian or Late Proterozoic) -- Medium-grained, light- to dark-green actinolite schist, actinofels, actinolite-chlorite schist, and much lesser talc-bearing rock. At many places the unit contains multiple foliations and a strong stretching lineation. CZmm Stromatic and lesser phlebitic migmatite consisting of quartz-plagioclase leucosome and quartz-rich schist paleosome. CZmp Fine-grained, lustrous, greenish-gray, red-brown weathering chlorite-sericite phyllonite that commonly is characterized by pods and knots of quartz that stand out on weathered surfaces. Much of the phyllonite had a migmatite protolith as relict leucosome can be seen in many outcrops. CZi Poorly to well-foliated sedimentary melange consisting of a medium-grained quartz-plagioclase-muscovite- biotite-chlorite-garnet matrix that contains fragments of quartz, foliated felsic and mafic metavolcanic rocks, metagabbro (CZg), Accotink Schist (CZa), and Lake Barcroft Metasandstone (CZl). Larger fragments are mapped. CZa Accotink Schist of Annandale Group (Early Cambrian and/or Late Proterozoic) -- Light-gray, fine- to medium-grained quartz-muscovite-biotite-chlorite schist. The unit grades up into Lake Barcroft metasandstone (CZl), the contact being placed where the rock in outcrop contains more than 50 percent metasandstone. CZl Lake Barcroft Metasandstone of Annandale Group (Early Cambrian and/or Late Proterozoic) -- Light- to medium-gray fine- to medium-grained meta-arenite and metagraywacke. The meta arenite beds are lenticular, are as much as 6 ft thick, and probably result from sedimentary amalgamation. The metagraywacke beds are generally regular, sharp, flat based, graded, and 4 to 6 in (10 to 15 cm) thick. SHAPE Shape Geometry 4 0 0 Feature geometry. ESRI Coordinates defining the features. GlobalID GlobalID GlobalID 38 0 0 SHAPE.area SHAPE.area Double 0 0 0 Area of each polygon. This field is calculated by ArcGIS automatically, and the units of measure are based on the Spatial Reference units of measure. SHAPE.len SHAPE.len Double 0 0 0 Perimeter length of each area. This field is calculated by ArcGIS automatically, and the units of measure are based on the Spatial Reference units of measure. 20100511 N/A Boundaries are not exact USGS geologic quad maps. Scanned paper maps 1:24,000 and up (various scales) Metadata imported. withheld 20060201 Dataset copied. withheld 20060811 Dataset copied. withheld 20060822 Dataset copied. withheld 20070119 None