README for U.S. Geological Survey Scientific Investigations Map 3429 TITLE: Geologic Map of the Ferncliff and Louisa Quadrangles, Louisa, Fluvanna, and Goochland Counties, Virginia By William C. Burton, Richard W. Harrison, Helen F. Malenda, Frank J. Pazzaglia, and E. Allen Crider Jr. ABSTRACT: The area encompassed by the geologic map of the Ferncliff and Louisa, Va., 7.5-minute quadrangles includes the hypothetical surface projection of the Quail fault, which is the subsurface fault that was responsible for the 2011 magnitude 5.8 (M5.8) Mineral, Va., earthquake. The mapping shows that the Quail fault appears to have reactivated the Harris Creek fault, a Paleozoic fault that has been named and mapped in the study area and marks the boundary between the Ellisville pluton neck and Chopawamsic Formation. The Harris Creek fault was reactivated earlier in the Mesozoic. Another result of the mapping is a well-defined, southwest to northeast, narrow zone of metagraywacke and ultramafic rocks (both part of the informal Shores complex) that marks the closure of a small ocean basin and the accretion of the 468- to 460-Ma Ordovician Chopawamsic volcanic arc (part of the Carolina terrane) onto Laurentia. The accretion zone is truncated by the Ordovician-Silurian (444 Ma) Ellisville pluton; the 444-Ma age of the pluton therefore represents the minimum age of the accretion zone and indicates likely closure of the ocean basin during the Taconic orogeny. Across the map area, the metamorphic grade ranges from lower-greenschist facies in the northwest to amphibolite facies in the southeast. 40Ar/39Ar age-dating across this metamorphic gradient indicates that Taconic metamorphism was overprinted by late-Paleozoic Alleghanian metamorphism that was accompanied by refolding and faulting of Taconic structures. Quaternary terraces mapped along the South Anna River record a long history of incision and downcutting. A continuing question is how much of this downcutting was a result of neotectonic uplift in the central Virginia seismic zone. This report consists of a single geologic map sheet and an online geographic information systems database that includes bedrock geologic unit contacts and polygons, surficial geologic polygons, faults, and structural geologic information. PURPOSE: The geologic map of the Ferncliff and Louisa, Va., 7.5-minute quadrangles is intended to serve as a foundation for applying geologic information to problems involving land use decisions, groundwater availability and quality, earth resources such as natural aggregate for construction, assessment of natural hazards (earthquakes), and engineering and environmental studies for waste disposal sites and construction projects. SUPPLEMENTARY INFORMATION: This digital database was compiled in compliance with the USGS National Cooperative Geologic Mapping Program (NCGMP09) geologic map database schema (https://ngmdb.usgs.gov/Info/standards/NCGMP09/) using ArcGIS version 10.6. This release is a file geodatabase that contains geologic map feature classes and stand-alone tables. ArcGIS-compatible GIS software is required to use the files of this database. The geodatabase is delivered in a single zipped folder in this release for ease of transfer. The scale of the source maps limits the usable spatial resolution of the database to 1:24,000 scale or greater. Feature classes are symbolized according to the FGDC Digital Cartographic Standard for Geologic Map Symbolization using ArcGIS Representation Classes where available. For more information about geologic map symbology, see the FGDC Digital Cartographic Standard for Geologic Map Symbolization web page (https://ngmdb.usgs.gov/fgdc_gds/geolsymstd.php). PROJECTION AND DATUM: All data is in North American Datum 1983 with Universal Traverse Mercator (UTM) projection, zone 17, North. MAP DOCUMENT: Contains layer files for this map. This map document was created in ArcGIS 10.6. This file is zipped with the geodatabase (FerncliffandLouisaVASIM3429.zip) FerncliffandLouisaVASIM3429.mxd GEODATABASE: The NCGMP09 compliant database contents are described below. FerncliffandLouisaVASIM3429.gdb..............................(Geodatabase) ================================================================================= GeologicMap.............................................(Feature dataset) ========================================================================= ContactsAndFaults..................................(Polyline feature class with FGDC compliant metadata) DataSourcePolys....................................(Polygon feature class with FGDC compliant metadata) GenericPoints......................................(Point feature class with FGDC compliant metadata) GenericSamples.....................................(Point feature class with FGDC compliant metadata) GeochronPoints.....................................(Point feature class with FGDC compliant metadata) GeologicLines......................................(Polyline feature class with FGDC compliant metadata) MapUnitOverlayPolys................................(Polygon feature class with FGDC compliant metadata) MapUnitPolys.......................................(Polygon feature class with FGDC compliant metadata) OrientationPoints..................................(Point feature class with FGDC compliant metadata) OtherPolys.........................................(Polygon feature class with FGDC compliant metadata) ========================================================================== DataSources.............................................(Non-spatial table with FGDC compliant metadata) DescriptionOfMapUnits...................................(Non-spatial table with FGDC compliant metadata) Glossary................................................(Non-spatial table with FGDC compliant metadata) METADATA: Metadata files are valid for both the geodatabase feature classes and open-access shapefiles. Metadata is contained in a single zipped folder (FerncliffandLouisaVASIM3429Metadata.zip) ================================================================================= GeologicMap.xml..............................................(Feature Dataset level FGDC compliant metadata) ContactsAndFaults.xml........................................(Feature class level FGDC compliant metadata) DataSourcePolys.xml..........................................(Feature class level FGDC compliant metadata) GenericPoints.xml............................................(Feature class level FGDC compliant metadata) GenericSamples.xml...........................................(Feature class level FGDC compliant metadata) GeochronPoints.xml...........................................(Feature class level FGDC compliant metadata) GeologicLines.xml............................................(Feature class level FGDC compliant metadata) MapUnitOverlayPolys.xml......................................(Feature class level FGDC compliant metadata) MapUnitPolys.xml.............................................(Feature class level FGDC compliant metadata) OrientationPoints.xml........................................(Feature class level FGDC compliant metadata) OtherPolys.xml...............................................(Feature class level FGDC compliant metadata) DataSources.xml..............................................(Non-spatial table FGDC compliant metadata) DescriptionOfMapUnits.xml....................................(Non-spatial table FGDC compliant metadata) Glossary.xml.................................................(Non-spatial table FGDC compliant metadata) BASEMAP: These files are contained in a single zipped folder (FerncliffandLouisaVASIM3429Basemap.zip). FerncliffandLouisaVACulture.tif FerncliffandLouisaVATopography.tif FerncliffandLouisaVAWater.tif FerncliffandLouisaVANeatline.shp FerncliffandLouisaVAWater.shp OPEN-ACCESS VERSIONS: To improve access to this product, an open-access version of these data are included with this release. Some field names may have been truncated when converting from geodatabase feature classes to shapefiles. A text file (logfile.txt) is available with information regarding changed field names. These files are available as a single zipped folder (FerncliffandLouisaVASIM3429OpenAccess.zip) ================================================================================= ContactsAndFaults.shp..............................(Polyline feature class with FGDC compliant metadata) DataSourcePolys.shp................................(Polygon feature class with FGDC compliant metadata) GenericPoints.shp..................................(Point feature class with FGDC compliant metadata) GenericSamples.shp.................................(Point feature class with FGDC compliant metadata) GeochronPoints.shp.................................(Point feature class with FGDC compliant metadata) GeologicLines.shp..................................(Polyline feature class with FGDC compliant metadata) MapUnitOverlayPolys.shp............................(Polygon feature class with FGDC compliant metadata) MapUnitPolys.shp...................................(Polygon feature class with FGDC compliant metadata) OrientationPoints.shp..............................(Point feature class with FGDC compliant metadata) OtherPolys.shp.....................................(Polygon feature class with FGDC compliant metadata) ================================================================================= DataSources.txt..............................................(Non-spatial table. Pipe delimited fields, pipe character = "|") DescriptionOfMapUnits.txt....................................(Non-spatial table. Pipe delimited fields, pipe character = "|") Glossary.txt.................................................(Non-spatial table. Pipe delimited fields, pipe character = "|") ================================================================================= DataSources.dbf..............................................(Non-spatial table) DescriptionOfMapUnits.dbf....................................(Non-spatial table) Glossary.dbf.................................................(Non-spatial table)