README for U.S. Geological Survey Scientific Investigations Map 3462 TITLE: Bedrock Geologic Map of the Springfield 7.5- x 15-Minute Quadrangle, Windsor County, Vermont, and Sullivan County, New Hampshire By: Gregory J. Walsh, Peter M. Valley, Thomas R. Armstrong, Nicholas M. Ratcliffe, Arthur J. Merschat, and Beau J. Gentry PREPARED IN COOPERATION WITH: Prepared in cooperation with the State of Vermont, Vermont Agency of Natural Resources, Vermont Geological Survey; and the State of New Hampshire, Department of Environmental Services, New Hampshire Geological Survey. ABSTRACT: The bedrock geology of the 7.5- by 15-minute Springfield quadrangle consists of highly deformed and metamorphosed Mesoproterozoic through Devonian metasedimentary and meta-igneous rocks. In the west, Mesoproterozoic gneisses of the Mount Holly Complex are the oldest rocks and form the eastern side of the Chester dome. The Moretown slice structurally overlies the Chester dome along the Keyes Mountain thrust fault which represents the Ordovician Taconic suture (Red Indian Line) between Laurentian and Ganderian crust. The allochthonous Cambrian through Ordovician Moretown slice includes the Moretown and Cram Hill Formations and the North River Igneous Suite. Silurian and Devonian metasedimentary and metavolcanic rocks of the Connecticut Valley trough (CVT) unconformably overlie the Moretown slice. Ordovician to Silurian and Devonian metasedimentary and metaigneous rocks of the New Hampshire sequence structurally overlie the CVT along the Devonian Acadian Monroe thrust fault. The oldest part of the New Hampshire sequence consists of Ordovician metamorphosed volcanic, plutonic, and sedimentary rocks of the Bronson Hill arc including the Ammonoosuc Volcanics, the Partridge Formation, and the Oliverian Plutonic Suite. The Ammonoosuc Volcanics are the base of the exposed section in the map area. The Bronson Hill arc (BHa) rocks are exposed in fault-bounded structural belts, including the Monroe thrust sheet, the Claremont belt, the Sugar River and Unity domes, and the footwall of the Brennan Hill thrust fault. Silurian to Devonian metasedimentary rocks of the Clough Quartzite, and Fitch and Littleton Formations unconformably overlie the Bronson Hill arc rocks. Devonian granitic and pegmatitic dikes and sills of the New Hampshire Plutonic Suite intruded previously deformed rocks. Devonian Acadian F1 fold nappes have a sheath fold geometry and are truncated by multiple generations of faults. The BHa structurally overlies the CVT along the Acadian Monroe fault with preserved tectonic melange in the footwall. Upright dome-stage F2 folds post-date amphibolite facies metamorphism and locally developed into sheath folds in high-strain zones. F3 folds exhibit sinistral rotation associated with Alleghanian lower-greenschist facies faults. Late Paleozoic Alleghanian to Mesozoic shear zones transpose stratigraphy, early structures, and peak metamorphic isograds. 40Ar/39Ar white mica growth ages (300-250 million years before present [Ma]) indicate that retrograde deformation continued into the latest Paleozoic and earliest Mesozoic. Apatite fission track data show that brittle faults were active prior to about 100 Ma and experienced Late Cretaceous and even Paleocene re-activation. The bedrock geology was mapped to study the tectonic history of the area and to provide a framework for ongoing characterization of the bedrock of Vermont and New Hampshire. This Scientific Investigations Map of the Springfield 7.5- x 15-minute quadrangle consists of sheets 1 and 2 as well as a geographic information system (GIS) database that includes bedrock geologic units, faults, outcrops, and structural geologic information. Sheet 1 of the report includes a bedrock geologic map, a correlation of map units, and a description of map units. Sheet 2 includes a discussion of the geology, references cited, two cross sections from the geologic map on sheet 1, a tectonic map showing major structural features, and a structural domain map showing the orientation of brittle features. SUPPLEMENTARY INFORMATION: This digital database was compiled in compliance with the USGS National Cooperative Geologic Mapping Program ("GeMS") geologic map database schema (https://ngmdb.usgs.gov/Info/standards/GeMS/) using ArcGIS version 10.7. 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, New Hampshire State Plane coordinate system (FIPS zone 2800), units in feet. MAP DOCUMENT: Contains layer files for this map. This map document was created in ArcGIS 10.7. This file is zipped with the geodatabase (sim3462_database.zip). SpringfieldNHVTSIM3462.mxd GEODATABASE: The "GeMS" compliant database contents are described below. SpringfieldNHVTSIM3462.gdb..............................(Geodatabase) ================================================================================= GeologicMap.............................................(Feature dataset) ========================================================================= CartographicLines..................................(Polyline feature class with FGDC compliant metadata) ContactsAndFaults..................................(Polyline feature class with FGDC compliant metadata) ContactsAndFaultsAnno..............................(Annotation feature class with FGDC compliant metadata) DataSourcePolys....................................(Polygon feature class with FGDC compliant metadata) GenericPoints......................................(Point feature class with FGDC compliant metadata) GenericPointsAnno..................................(Annotation feature class with FGDC compliant metadata) GeochronPoints.....................................(Point feature class with FGDC compliant metadata) GeochronPointsAnno.................................(Annotation feature class with FGDC compliant metadata) GeologicLines......................................(Polyline feature class with FGDC compliant metadata) GeologicLinesAnno..................................(Annotation feature class with FGDC compliant metadata) MapUnitOverlayPolys................................(Polygon feature class with FGDC compliant metadata) MapUnitPolys.......................................(Polygon feature class with FGDC compliant metadata) MapUnitPolysAnno...................................(Annotation feature class with FGDC compliant metadata) OrientationPoints..................................(Point feature class with FGDC compliant metadata) OrientationPointsAnno..............................(Annotation feature class with FGDC compliant metadata) OverlayPolys.......................................(Polygon feature class with FGDC compliant metadata) Stations...........................................(Point feature class with FGDC compliant metadata) ========================================================================== DataSources.............................................(Non-spatial table with FGDC compliant metadata) DescriptionOfMapUnits...................................(Non-spatial table with FGDC compliant metadata) GeoMaterialDict.........................................(Non-spatial table with FGDC compliant metadata) Glossary................................................(Non-spatial table with FGDC compliant metadata) RepurposedSymbols.......................................(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 (sim3462_metadata.zip). ================================================================================= GeologicMap.xml..............................................(Feature Dataset level FGDC compliant metadata) CartographicLines.xml........................................(Feature class level FGDC compliant metadata) ContactsAndFaults.xml........................................(Feature class level FGDC compliant metadata) ContactsAndFaultsAnno.xml....................................(Annotation feature class FGDC compliant metadata) DataSourcePolys.xml..........................................(Feature class level FGDC compliant metadata) GenericPoints.xml............................................(Feature class level FGDC compliant metadata) GenericPointsAnno.xml........................................(Annotation feature class FGDC compliant metadata) GeochronPoints.xml...........................................(Feature class level FGDC compliant metadata) GeochronPointsAnno.xml.......................................(Annotation feature class FGDC compliant metadata) GeologicLines.xml............................................(Feature class level FGDC compliant metadata) GeologicLinesAnno.xml........................................(Annotation feature class FGDC compliant metadata) MapUnitOverlayPolys.xml......................................(Feature class level FGDC compliant metadata) MapUnitPolys.xml.............................................(Feature class level FGDC compliant metadata) MapUnitPolysAnno.xml.........................................(Annotation feature class FGDC compliant metadata) OrientationPoints.xml........................................(Feature class level FGDC compliant metadata) OrientationPointsAnno.xml....................................(Annotation feature class FGDC compliant metadata) OverlayPolys.xml.............................................(Feature class level FGDC compliant metadata) Stations.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) GeoMaterialDict.xml..........................................(Non-spatial table FGDC compliant metadata) RepurposedSymbols.xml........................................(Non-spatial table FGDC compliant metadata) BASEMAP: These files are contained in a single zipped folder (sim3462_basemap.zip). SpringfieldNHVTSIM3462Culture.tif SpringfieldNHVTSIM3462Topography.tif SpringfieldNHVTSIM3462Water.tif SpringfieldNHVTSIM3462Water.shp OPEN-ACCESS VERSIONS: To improve access to this product, open-access versions of these data are included with this release. Two folders are available; SpringfieldNHVTSIM3462-open contains all database elements as shapefiles with corresponding tables presented as comma delimited files (.csv) and (or) text files (.txt). SpringfieldNHVTSIM3462-simple contains simplified shapefiles with "GeMS" tables added as additional fields within individual corresponding shapefiles. These folders are available as a single zipped folder (sim3462_openaccess.zip). 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.