Joel E. Robinson Peter W. Lipman 20200310 Vector Digital Data Set (Polyline) Data Release P911OL4Q Reston, VA U.S. Geological Survey https://doi.org/10.5066/P911OL4Q Peter W. Lipman 2020 Publication (Map) Scientific Investigations Map SIM 3394 Reston, VA U.S. Geological Survey https://doi.org/10.3133/sim3394 The San Juan Mountains in southwestern Colorado have long been recognized as a site of exceptionally voluminous mid-Tertiary volcanism, including at least 24 major ignimbrite sheets (each 150-5,000 km3) and associated caldera structures active at 33-23 Ma. More recent volcanologic and petrologic studies in the San Juan region have focused mainly on several ignimbrite-caldera systems: the southeastern area (Platoro complex), western calderas (Uncompahgre-Silverton-Lake City), the central cluster (La Garita-Creede calderas). The northeast San Juan region that was far less studied until recently occupies a transition between earlier volcanism in central Colorado and the larger-volume younger ignimbrite-caldera foci farther south and west. The present study of the Bonanza area evaluates eruptive and magmatic processes of silicic Cordilleran volcanism in this northeast region, based on new geologic mapping (mainly summers of 2007-12) and concurrent petrologic and geochronologic analysis. The resulting map is based on new field mapping of volcanic rocks in thirteen 7.5-minute quadrangles in northeastern parts of the volcanic field, petrologic studies involving several hundred new chemical analyses, and high-resolution age determinations for about 130 sites. The Bonanza center contains exceptionally complete and diverse features of an ignimbrite caldera cycle, including voluminous andesite erupted before and after ignimbrite eruptions, complex compositional zonation within both the outflow ignimbrite sheet and the tuff concurrently ponded within the caldera, extensive portions of the ring-fault system that accommodated subsidence, thick compositionally diverse lavas that filled the caldera after subsidence, remnants of the original topographic caldera rim, widespread erosional exposure of caldera-floor features, and postcaldera granitic intrusions that generated a notably steep resurgent dome within the caldera. This database was constructed in order to produce a geologic map as a basis for understanding volcanic processes involved in the creation of the Bonanza and Marshall calderas. This database contains file geodatabase feature classes describing geologic lines and polygons, faults, caldera boundaries, geochronology, and rock chemistry. This metadata file was written to provide an overview description of the complete database. Any shapefiles derived from the geodatabase may have abbreviated or shortened field names. 2007 2012 ground condition Complete None planned -106.385044268 -105.872598138 38.504779047 37.996210253 Alexandria Digital Library Feature Type Thesaurus volcanoes geology USGS Thesaurus geology None caldera explosive eruptions USGS Metadata Identifier USGS:5e1f8f74e4b0ecf25c632d9e Common geographic areas Colorado Saguache North America United States Bonanza None. Please see 'Distribution Info' for information on where you can download the data. Uses of this digital geologic map should not violate the spatial resolution of the data. Although the digital form of the data removes the constraint imposed by the scale of a paper map, the detail and accuracy inherent in map scale are also present in the digital data. The fact that this database was edited for a scale of 1:24,000 means that higher resolution information is not present in the dataset. Plotting at scales larger than 1:24,000 will not yield greater real detail, although it may reveal fine-scale irregularities below the intended resolution of the database. Similarly, where this database is used in combination with other data of higher resolution, the resolution of the combined output will be limited by the lower resolution of these data. Acknowledgement of the U.S. Geological Survey would be appreciated in products derived from these data. U.S. Geological Survey, ALASKA REGION Joel E Robinson Geologist mailing address

345 Middlefield Road

Mail Stop 910

Menlo Park CA 94025 650-439-2322 650-329-5203 jrobins@usgs.gov Geology mapped by P.W. Lipman (2007-2012); assisted by Andrea Sbisa; (2009-2011); GIS database by Joel Robinson; Edited by J.L. Zigler; digital cartographic production by E. Allen Crider Jr. and Katie Sullivan; Manuscript approved for publication December 12, 2018 Environment as of Metadata Creation: Microsoft [Unknown] Version 6.2 (Build 9200) ; Esri ArcGIS 10.6 (Build 8321) Service Pack N/A (Build N/A) No formal attribute accuracy tests were conducted. Polygon and arc (chain-node) topology present in appropriate feature classes. Other feature classes are point, annotation or raster and do not require topologic relationships. The data set is intended to describe completely the igneous and volcanic products, and volcanic vent locations at 1:24,000 scale. Geological information appropriately mapped at larger scale has been omitted. Data set is considered complete for the information presented, as described in the abstract. The position of each feature in the database is derived from a USGS 1:24,000 topographic base map or with a GPS. The positional accuracy of each feature is indicated quantitatively within the LocationConfidenceMeters field in the attribute table. In general, features in the database are well located. A formal accuracy assessment of the vertical positional information in the data set has either not been conducted, or is not applicable. Geology was compiled on USGS 1:24,000-scale topographic maps (or fieldsheets) by Peter Lipman. Joel Robinson scanned the fieldsheets at 400 dpi, and georeferenced the scans. Linework was converted to vector data using heads-up-digitizing. Polygon topology was created and each arc and polygon tagged on-screen. Points features were also then added from the scanned fieldsheets through head-up-digitizing. 2011 The digitized geology was then combined with topography and plotted to be checked by the authors. 2020 Vector Complete Chain 124 G-polygon 13 Entity point 295 Entity point 144 Entity point 55 Complete Chain 6733 GT-polygon composed of chains 124 Entity point 843 GT-polygon composed of chains 4698 G-polygon 6131 Universal Transverse Mercator 13 0.9996 -105.0 0.0 500000.0 0.0 coordinate pair 0.6096 0.6096 Meter D_North_American_1983 GRS_1980 6378137.0 298.257222101 This metadata file was written to provide an overview for the complete database in geodatabase format. Shapefiles derived from the geodatabase may have abbreviated or shortened field names. For more descriptive descriptions of the attributes please see the metadata files associated with each feature class. The database contains one feature dataset, GeologicMap. The GeologicMap feature dataset contains the feature classes that store the geologic data. In addition to the feature dataset, this database contains four tables. Below is an attribute overview for the features found in the feature classes and tables. Detailed metadata files can be found associated with the other feature classes. There are two line feature classes: ContactsAndFaults, and GeologicLines. The ContactsAndFaults feature class contains the locations of the geologic contacts, faults, dikes, scarps, and water boundaries. The Type field contains the designations for each, and IsConcealed, ExistenceConfidence, IdentityConfidence, and LocationConfidence fields contain whether the object is concealed, how well the author can recognize the line, and how well the author can locate the line. The GeologicLines feature class contains the locations of synclines, anticlines, hinges, and caldera boundaries. These feature classes also contain other fields specified by the GeMS database schema. There are three polygon feature classes: QuadBoundariesPolys, MapUnitPolys, and OtherPolys. The QuadBoundariesPolys feature class contains the boundaries for each of the USGS 7.5-minute quadrangles and the NAME field stores the name of each quad. The MapUnitPolys feature class contains the boundaries for geologic units. Geologic unit symbols for each polygon is stored in the MapUnit field, and IdentityConfidence describes how well the author can identify the map unit at this location. MapUnit can be joined or related to the DescriptionsOfMapUnits table using the MapUnit field for geologic unit symbol, complete geologic unit names and descriptions. The OtherPolys feature class contains the boundaries of altered rock. These feature classes also contain other fields specified by the GeMS database schema. There are four point feature classes in this release, GeochemPoints, GeochronPoints, OrientationPoints, and VolcanicPoints. The VolcanicPoints feature class contains the locations of syn-eruptive landslide breccia. The OrientationPoints feature class contains the locations of bedding and structural measurements. The Type, Azimuth, and Inclination fields contain the data describing the measurement. The GeochemPoints feature class contains the sample locality and all of the geochemistry measurements. The GeochronPoints feature class contains the locations of the geochronology measurements taken. The author's preferred age is listed in the PreferredAge field with PreferredAgeError. Other fields are dedicated to describing other 40Ar/39Ar age determinations. These feature classes also contain other fields specified by the GeMS database schema. The database also contains four tables: DataSources, DescriptionOfMapUnits, GeoMaterialDict, and Glossary. The DataSources table contains the references used in the creation of this map. The DataSourcesID is the foreign key to the DataSources_ID field in all other tables. The DescriptionOfMapUnits table contains the geologic unit symbol, complete geologic unit name, age, and description for each of the geologic unit symbols on the map in the MapUnit, Name, Age, and Description fields. The GeoMaterialDict table contains the standard definitions for the geomaterials found in the DescriptionOfMapUnits table. This is a standard default GeMS table. The Glossary table provides definitions in the Definition field for many of the terms used in the database. These tables also contain other fields specified by the GeMS database schema. Finally, this release contains an annotation feature class, Combined_Annotation. This feature class provides cartographic names and labels for the map. All fields are specified by ESRI. The entity and attribute information was generated by the individual and/or agency identified as the originator of the data set. Please review the rest of the metadata record for additional details and information. U.S. Geological Survey Mailing

Denver Federal Center

Box 25286

Denver Colorado 80225-0046 US 1-888-ASK-USGS (303)202-4695 infoservices@usgs.gov This database has been approved for release and publication by the Director of the U.S. Geological Survey (USGS). Although this database has been subjected to rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is released on condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use. Vector Digital Data Set (Polyline) https://doi.org/10.5066/P911OL4Q None. No fees are applicable for obtaining the data set. 20200831 Joel E Robinson U.S. Geological Survey, ALASKA REGION Geologist mailing address

345 Middlefield Road

Mail Stop 910

Menlo Park CA 94025 650-439-2322 650-329-5203 jrobins@usgs.gov FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998