Identification_Information: Citation: Citation_Information: Originator: Joel E. Robinson Originator: Peter W. Lipman Publication_Date: 2012 Title: Database for the Geologic Map of the Cochetopa Park and North Pass Calderas, Northeastern San Juan Mountains, Colorado Geospatial_Data_Presentation_Form: vector digital data Series_Information: Series_Name: Scientific Investigations Map Issue_Identification: SIM 3123 Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Online_Linkage: http://pubs.usgs.gov/sim/3123 Larger_Work_Citation: Citation_Information: Originator: Peter W. Lipman Publication_Date: 2012 Title: Geologic Map of the Cochetopa Park and North Pass Calderas, Northeastern San Juan Mountains, Colorado Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: Scientific Investigations Map Issue_Identification: SIM 3123 Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Online_Linkage: http://pubs.usgs.gov/sim/3123 Description: Abstract: The San Juan Mountains in southwestern Colorado have long been known as a site of exceptionally voluminous middle Tertiary volcanism, including at least 22 major ignimbrite sheets (each 150-5,000 cubic km) and associated caldera structures active at 33-23 Ma. Recent volcanologic and petrologic studies in the San Juan region have focused mainly on several ignimbrite-caldera systems: the southeastern area, western calderas, and the central cluster. This study focused on the northeast San Juan region, which occupies a transition between earlier volcanism in central Colorado and large-volume younger ignimbrite-caldera foci farther south and west. The present map is based on new field coverage of volcanic rocks in seventeen 7.5" quadrangles in northeastern parts of the volcanic field, high-resolution age determinations for 120 new sites, and petrologic studies involving several hundred new chemical analyses. The new mapping and accompanying lab results (1) document volcanic evolution of the previously unrecognized North Pass caldera and the morphologically beautifully preserved but enigmatic Cochetopa basin, including unique features not previously described from ignimbrite calderas elsewhere; (2) provide evidence for a more rapid recurrence of large ignimbrite eruptions than previously known elsewhere; and (3) quantify the regional time-space-volume progression from the earlier Sawatch magmatic trend southward into the San Juan region. Purpose: This database was constructed in order to produce a geologic map as a basis for understanding processes involved in the eruptions that built the Cochetopa Park and North Pass calderas, Northeastern San Juan Mountains, Colorado. Supplemental_Information: This database contains geodatabase feature classes describing the geologic lines and polygons, faults, caldera boundaries, and rock chemistry, and a grid of the topographic base. This metadata file provides an overview for all of these files. For more detailed metadata, please see the metadata provided with each individual coverage. Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 2000 Ending_Date: 2006 Currentness_Reference: ground condition Status: Progress: Complete Maintenance_and_Update_Frequency: None planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -107.007661 East_Bounding_Coordinate: -106.369082 North_Bounding_Coordinate: 38.506242 South_Bounding_Coordinate: 37.993744 Keywords: Theme: Theme_Keyword: volcanoes Theme_Keyword: geology Theme_Keyword: caldera Theme_Keyword: explosive eruptions Theme_Keyword: lava flows Theme_Keyword: breccia Place: Place_Keyword: United States of America Place_Keyword: Colorado Place_Keyword: Cochetopa Park, CO Place_Keyword: North Pass, CO Place_Keyword: central San Juan mountains Temporal: Temporal_Keyword: Quaternary Temporal_Keyword: Holocene Temporal_Keyword: Pleistocene Temporal_Keyword: Pliocene Temporal_Keyword: Tertiary Temporal_Keyword: Oligocene Temporal_Keyword: Miocene Access_Constraints: none Use_Constraints: 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 data was edited at a scale of 1:24,000 and 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. Acknowlegdment of the U.S. Geological Survey would be appreciated in products derived from these data. Point_of_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey Contact_Person: Joel E. Robinson Contact_Position: Geologist Contact_Address: Address_Type: mailing address Address: 345 Middlefield Road Address: MS 910 City: Menlo Park State_or_Province: California Postal_Code: 94025 Country: USA Contact_Electronic_Mail_Address: jrobins@usgs.gov Security_Information: Security_Classification: Unclassified Native_Data_Set_Environment: Microsoft Windows 2000 Version 5.2 (Build 3790) Service Pack 2; ESRI ArcCatalog 9.3.0.1770 Data_Quality_Information: Logical_Consistency_Report: 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. Completeness_Report: The report 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. Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: Well located data items are intended to have a horizontal positional accuracy better than 0.5 mm at 1:24,000 scale, or within 12 meters on the ground. The general positional accuracy of each line in the database is indicated qualitatively within the LTYPE field in the Arc Attribute Table (see Attribute_Domain_Values). Points in the database are generally well located. The position of each data item is derived from a USGS 1:24,000 topographic base map, and therefore additional inaccuracies may also be encountered that are within National Map Accuracy Standards. Vertical_Positional_Accuracy: Vertical_Positional_Accuracy_Report: No vertical positional data recorded Lineage: Source_Information: Source_Citation: Citation_Information: Originator: Fridrich, C.J. Originator: DeWitt, E. Originator: Bryant, B. Originator: Richard, S. Originator: Smith, R.P. Publication_Date: 1998 Title: Geologic map of the Collegiate Peaks Wilderness area and the Grizzly Peak caldera, Sawatch Range, central Colorado Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: U.S. Geological Survey Miscellaneous Investigations Map Issue_Identification: I-2565 Publication_Information: Publication_Place: Reston, VA. Publisher: U.S. Geological Survey Type_of_Source_Media: paper Source_Time_Period_of_Content: Source_Currentness_Reference: publication date Source_Citation_Abbreviation: Fridrich and others, 1998 Source_Information: Source_Citation: Citation_Information: Originator: Hedlund, D.C. Originator: Olson J.C. Publication_Date: 1974 Title: Geologic map of the Iris NW quadrangle, Gunnison and Saguache Counties, Colorado Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: U.S. Geological Survey Geologic Quadrangle Map Issue_Identification: GQ-1134 Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Source_Scale_Denominator: 1:24,000 Type_of_Source_Media: paper Source_Time_Period_of_Content: Source_Currentness_Reference: publication date Source_Citation_Abbreviation: Hedlund and Olson, 1974 Source_Information: Source_Citation: Citation_Information: Originator: Lipman, P.W. Publication_Date: 1976 Title: Geologic map of the Lake City caldera, western San Juan Mountains, Colorado Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: U.S. Geological Survey Map Miscellaneous Investigations Series Issue_Identification: I-962 Publication_Information: Publication_Place: Reston, VA Publisher: U.S Geological Survey Type_of_Source_Media: paper Source_Time_Period_of_Content: Source_Currentness_Reference: publication date Source_Citation_Abbreviation: Lipman, 1976 Source_Information: Source_Citation: Citation_Information: Originator: Lipman, P.W. Publication_Date: 2006 Title: Geologic map of the central San Juan caldera complex, southwestern Colorado Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: Geologic Investigations Series Issue_Identification: I-2799 Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Online_Linkage: http://pubs.usgs.gov/imap/i2799/ Source_Scale_Denominator: 1:50,000 Type_of_Source_Media: paper Source_Time_Period_of_Content: Source_Currentness_Reference: publication date Source_Citation_Abbreviation: Lipman, 2006 Source_Information: Source_Citation: Citation_Information: Originator: Olson, J.C. Publication_Date: 1974 Title: Geologic map of the Rudolph Hill quadrangle, Gunnison Hinsdale, and Saguache Counties, Colorado Series_Information: Series_Name: U.S. Geological Survey Geologic Quadrangle Map Issue_Identification: GQ-1177 Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Source_Scale_Denominator: 1:24,000 Type_of_Source_Media: paper Source_Time_Period_of_Content: Source_Currentness_Reference: publication date Source_Citation_Abbreviation: Olson, 1974 Source_Information: Source_Citation: Citation_Information: Originator: Olson, J.C. Publication_Date: 1976 Title: Geologic map of the Houston Gulch quadrangle, Gunnison and Saguache Counties, Colorado Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: U.S. Geological Survey Geologic Quadrangle Map Issue_Identification: GQ-1287 Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Source_Scale_Denominator: 1:24,000 Type_of_Source_Media: paper Source_Time_Period_of_Content: Source_Currentness_Reference: publication date Source_Citation_Abbreviation: Olson, 1976 Source_Information: Source_Citation: Citation_Information: Originator: Olson, J.C. Publication_Date: 1976 Title: Geologic map of the Iris quadrangle, Gunnison and Saguache Counties, Colorado Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: U.S. Geological Survey Quadrangle Map Issue_Identification: GQ-1286 Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Source_Scale_Denominator: 1:24,000 Type_of_Source_Media: paper Source_Time_Period_of_Content: Source_Currentness_Reference: publication date Source_Citation_Abbreviation: Olson, 1976 Source_Information: Source_Citation: Citation_Information: Originator: Olson, J.C Publication_Date: 1983 Title: Geologic and structural maps and sections of the Marshall Pass Mining District, Saguache, Gunnison, and Chafee Counties, Colorado Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: U.S. Geological Survey Miscellaneous Investigations Series Issue_Identification: I-1425 Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Source_Scale_Denominator: 1;24,000 Type_of_Source_Media: paper Source_Time_Period_of_Content: Source_Currentness_Reference: publication date Source_Citation_Abbreviation: Olson, 1983 Source_Information: Source_Citation: Citation_Information: Originator: Olson, J.C. Originator: Steven T.A. Originator: Hedlund, D.C. Publication_Date: 1975 Title: Geologic map of the Spring Hill Creek quadrangle, Saguache County, Colorado Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: U.S. Geological Survey Miscellaneous Field Studies Issue_Identification: MF-713 Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Source_Scale_Denominator: 1:24,000 Type_of_Source_Media: paper Source_Time_Period_of_Content: Source_Currentness_Reference: publication date Source_Citation_Abbreviation: Olson and others, 1975 Source_Information: Source_Citation: Citation_Information: Originator: Olson, J.C. Originator: Steven T.A. Publication_Date: 1976 Title: Geologic map of the Sawtooth Mountain quadrangle, Saguache County, Colorado Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: U.S. Geological Survey Miscellaneous Field Studies Issue_Identification: MF-733 Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Source_Scale_Denominator: 1:24,000 Type_of_Source_Media: paper Source_Citation_Abbreviation: Olson and Steven, 1976 Source_Information: Source_Citation: Citation_Information: Originator: Olson, J.C. Originator: Steven T.A. Publication_Date: 1976 Title: Geologic map of the Razor Creek Dome quadrangle, Saguache County, Colorado Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: U.S. Geological Survey Miscellaneous Field Studies Issue_Identification: MF-748 Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Source_Scale_Denominator: 1:24,000 Type_of_Source_Media: paper Source_Time_Period_of_Content: Source_Currentness_Reference: publication date Source_Citation_Abbreviation: Olson and Steven, 1976 Source_Information: Source_Citation: Citation_Information: Originator: Steven, T.A. Publication_Date: 1967 Title: Geologic map of the Bristol Head quadrangle, Mineral and Hinsdale Counties, Colorado Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: U.S. Geological Survey Geologic Quadrangle Map Issue_Identification: GQ-631 Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Type_of_Source_Media: paper Source_Time_Period_of_Content: Source_Currentness_Reference: publication date Source_Citation_Abbreviation: Steven, 1967 Source_Information: Source_Citation: Citation_Information: Originator: Steven, T.A. Originator: Hon, Ken Originator: Lanphere, M.A. Publication_Date: 1995 Title: Neogene geomorphic evolution of the central San Juan Mountains near Creede, Colorado Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: U.S. Geological Survey Miscellaneous Investigations Series Issue_Identification: I-2504 Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Type_of_Source_Media: paper Source_Time_Period_of_Content: Source_Currentness_Reference: publication date Source_Citation_Abbreviation: Steven and others, 1995 Source_Information: Source_Citation: Citation_Information: Originator: Steven, T.A. Originator: Hail, W.J. Publication_Date: 1989 Title: Geologic map of the Montrose 30' x 60' quadrangle, southwestern Colorado Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: U.S. Geological Survey Miscellaneous Geologic Investigations Issue_Identification: I-1399 Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Source_Scale_Denominator: 1:100,000 Type_of_Source_Media: paper Source_Time_Period_of_Content: Source_Currentness_Reference: publication date Source_Citation_Abbreviation: Steven and Hail, 1989 Source_Information: Source_Citation: Citation_Information: Originator: Steven, T.A. Originator: Lipman P.W. Originator: Hail, W.J., Jr. Originator: Barker, Fred Originator: Luedke, R.G. Publication_Date: 1974 Title: Geologic map of the Durango quadrangle, southwestern Colorado Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: U.S. Geological Survey Miscellaneous Geologic Investigations Series Issue_Identification: I-764 Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Source_Scale_Denominator: 1:250,000 Type_of_Source_Media: paper Source_Time_Period_of_Content: Source_Currentness_Reference: publication date Source_Citation_Abbreviation: Steven and others, 1974 Source_Information: Source_Citation: Citation_Information: Originator: Steven, T.A. Originator: Ratté, J.C. Publication_Date: 1973 Title: Geologic map of the Creede quadrangle, Mineral and Saguache Counties, Colorado Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: U.S. Geology Survey Geologic Quadrangle Map Issue_Identification: GQ-1053 Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geology Survey Type_of_Source_Media: paper Source_Time_Period_of_Content: Source_Currentness_Reference: publication date Source_Citation_Abbreviation: Steven and Ratté, 1973 Source_Information: Source_Citation: Citation_Information: Originator: Stork, A. Originator: Coogan, J.C. Originator: Fillmore, Csar, A. Originator: Wentz, R. Publication_Date: 2006 Title: Geologic Map of the Gunnison Quadrangle, Gunnison County, Colorado Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: Colorado Department of Natural Resources Open-File Report Issue_Identification: Open-File Report 06-04 Publication_Information: Publisher: Colorado Department of Natural Resources Source_Scale_Denominator: 1:24,000 Type_of_Source_Media: paper Source_Time_Period_of_Content: Source_Currentness_Reference: publication date Source_Citation_Abbreviation: Stork and others, 2006 Source_Information: Source_Citation: Citation_Information: Originator: Stork, A. Originator: Coogan, J.C. Originator: Fillmore, R. Originator: Brunkal, H. Originator: Nicolette, J. Originator: Payton, A. Publication_Date: 2007 Title: Geologic Map of the Signal Peak Quadrangle, Gunnison County, Colorado Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: Colorado Department of Natural Resources Open-File Report Issue_Identification: Open-File Report 07-03 Publication_Information: Publisher: Colorado Department of Natural Resources Source_Scale_Denominator: 1:24,000 Type_of_Source_Media: paper Source_Time_Period_of_Content: Source_Currentness_Reference: publication date Source_Citation_Abbreviation: Stork and others, 2007 Source_Information: Source_Citation: Citation_Information: Originator: Tweto, O. Publication_Date: 1979 Title: Geologic map of Colorado Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: U.S. Geological Survey Special Map Issue_Identification: The Geologic Map of Colorado Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Source_Scale_Denominator: 1:500,000 Type_of_Source_Media: paper Source_Time_Period_of_Content: Source_Currentness_Reference: publication date Source_Citation_Abbreviation: Tweto, 1979 Source_Information: Source_Citation: Citation_Information: Originator: Tweto, O. Originator: Steven, T.A. Originator: Hail, W.J., Jr. Originator: Moench, R.H. Publication_Date: 1976 Title: Preliminary geologic map of the Montrose 1 degree x 2 degree quadrangle, southwestern Colorado Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: U.S. Geological Survey Miscellaneous Field Studies Map Issue_Identification: MF-761 Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Type_of_Source_Media: paper Source_Citation_Abbreviation: Tweto and others, 1976 Process_Step: Process_Description: Geologic linework was compiled on USGS 1:24,000 topographic maps by Peter W. Lipman. Joel Robinson then scanned the geologic linework at 400 dpi and georeferenced the scans. He converted the linework to vector data using head-up-digitizing. Polygon topology was created and each arc and polygon tagged on-screen. Plotfiles were created and quadrangles were then plotted with topography to be checked by the authors. Process_Date: 2005-2008 Process_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey Contact_Person: Joel E. Robinson Contact_Position: Geologist Contact_Address: Address_Type: mailing address Address: 345 Middlefield Road Address: MS 910 City: Menlo Park State_or_Province: California Postal_Code: 94025 Country: USA Contact_Voice_Telephone: (650)329-5322 Contact_Electronic_Mail_Address: jrobins@usgs.gov Spatial_Data_Organization_Information: Direct_Spatial_Reference_Method: Vector Point_and_Vector_Object_Information: SDTS_Terms_Description: SDTS_Point_and_Vector_Object_Type: String Point_and_Vector_Object_Count: 7109 SDTS_Terms_Description: SDTS_Point_and_Vector_Object_Type: G-polygon Point_and_Vector_Object_Count: 4539 SDTS_Terms_Description: SDTS_Point_and_Vector_Object_Type: String Point_and_Vector_Object_Count: 400 SDTS_Terms_Description: SDTS_Point_and_Vector_Object_Type: G-polygon Point_and_Vector_Object_Count: 19 SDTS_Terms_Description: SDTS_Point_and_Vector_Object_Type: Entity point Point_and_Vector_Object_Count: 193 SDTS_Terms_Description: SDTS_Point_and_Vector_Object_Type: Entity point Point_and_Vector_Object_Count: 344 SDTS_Terms_Description: SDTS_Point_and_Vector_Object_Type: Entity point Point_and_Vector_Object_Count: 329 SDTS_Terms_Description: SDTS_Point_and_Vector_Object_Type: Entity point Point_and_Vector_Object_Count: 142 Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Planar: Map_Projection: Map_Projection_Name: Lambert Conformal Conic Lambert_Conformal_Conic: Standard_Parallel: 37.233333 Standard_Parallel: 38.433333 Longitude_of_Central_Meridian: -105.500000 Latitude_of_Projection_Origin: 36.666667 False_Easting: 609601.219202 False_Northing: 0.000000 Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: coordinate pair Coordinate_Representation: Abscissa_Resolution: 0.000032 Ordinate_Resolution: 0.000032 Planar_Distance_Units: meters Geodetic_Model: Horizontal_Datum_Name: North American Datum of 1927 Ellipsoid_Name: Clarke 1866 Semi-major_Axis: 6378206.400000 Denominator_of_Flattening_Ratio: 294.978698 Vertical_Coordinate_System_Definition: Altitude_System_Definition: Altitude_Resolution: 0.000003 Altitude_Encoding_Method: Explicit elevation coordinate included with horizontal coordinates Entity_and_Attribute_Information: Detailed_Description: Entity_Type: Entity_Type_Label: geology_arc Entity_Type_Definition: Feature class containing the geologic lines. Entity_Type_Definition_Source: author Detailed_Description: Entity_Type: Entity_Type_Label: geology_poly Entity_Type_Definition: Feature class delineating the boundaries of the geologic units. Entity_Type_Definition_Source: author Detailed_Description: Entity_Type: Entity_Type_Label: quad_bndry Entity_Type_Definition: Feature class contains the boundaries of the mapped USGS quadrangles. Entity_Type_Definition_Source: USGS Detailed_Description: Entity_Type: Entity_Type_Label: alteration_poly Entity_Type_Definition: Feature class delineating areas that have undergone hydrothermal alteration Entity_Type_Definition_Source: author Detailed_Description: Entity_Type: Entity_Type_Label: ArArLocations Entity_Type_Definition: Feature class containing the point locations of samples collected for Ar/Ar geochronology Entity_Type_Definition_Source: author Detailed_Description: Entity_Type: Entity_Type_Label: caldera_arc Entity_Type_Definition: Feature class containing the caldera boundaries Entity_Type_Definition_Source: author Detailed_Description: Entity_Type: Entity_Type_Label: ChemLocations Entity_Type_Definition: Feature class containing point locations of samples taken for geochemistry Entity_Type_Definition_Source: author Detailed_Description: Entity_Type: Entity_Type_Label: geology_points Entity_Type_Definition: Feature class containing point locations of strucutral measurements Entity_Type_Definition_Source: author Detailed_Description: Entity_Type: Entity_Type_Label: sample_points Entity_Type_Definition: Feaure class containing the point locations of age samples used on printed map. Entity_Type_Definition_Source: author Overview_Description: Entity_and_Attribute_Overview: The metatdata file was written to provide an overview for the complete database. For more informative descriptions of the attributes please see the metadate files associated with each feature class. There is one line feature class, geology_arc. The geology_arc feature class contains the geologic contacts, faults, dikes, scarps, and water boundaries. The LTYPE attribute describes the type of line and its positional certainty. The other associated fields are defined by the software and are described more specifically in the detailed metadata file associated with the coch_geo_arc feature class. The map_bndry_arc feature class contains no additional descriptive attributes. There are three polygon feature classes: geology_poly, alteration_poly, and quad_bndry. The unit_label attribute in the geology_poly feature class contains the geologic unit symbols for each polygon. These geologic unit symbols can be correlated or related to geologic names and descriptions by using the unit_descriptions table contained in this database. The alterations_poly feature class delinieates the areas that have under gone hydrothermal alteration. No additional attributes are stored here. The quad_bndry feature class contains its quadrangle name in the Name attribute. The feature class also contains several other attributes that describe the location of the quadrangle within the structure of the USGS system. There are two point feature classes in this release, ArLocations and ChemLocations. The ArLocations feature class contains the location of rock samples used to calculate Ar-Ar age data. The SampleID field contains the author's sample id and the Location field gives a brief description of the locations. The ChemLocations feature class contains the location of rock samples used to for rock geochemistry. The SampleID field contains the author's sample id and the Quad field provides an abbrieviation of the quadrangle name. The release also contains three tables. The unit_descriptions table contains the complete geologic unit name and description for each of the geologic unit symbol on the map. The other two tables contain sample chemistry and age data. ArData contains Ar-Ar derived age data. The age is contained in the Age(Ma) field. This table is related to ArLocations through the RelateID field . ChemData contains the chemical analysis of the major elements from three techniques. This table is related to ChemLocations through the RelateID field. For more detailed description on each field see the more detailed metadata associated with the table. Distribution_Information: Distributor: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey Contact_Person: USGS Information Services Contact_Address: Address_Type: mailing address Address: Box 25286 Address: Denver Federal Center City: Denver State_or_Province: Colorado Postal_Code: 80225-0046 Country: USA Contact_Voice_Telephone: (303)202-4200 Contact_Voice_Telephone: 1-888-ASK-USGS Contact_Facsimile_Telephone: (303)202-4695 Contact_Electronic_Mail_Address: infoservices@usgs.gov Resource_Description: These files are integral to the U.S. Geological Survey Scientific Investigations Map 3123. Distribution_Liability: 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. Standard_Order_Process: Digital_Form: Digital_Transfer_Information: Format_Name: ESRI geodatabase File_Decompression_Technique: WinZip Transfer_Size: 44.7 Mb Digital_Transfer_Option: Online_Option: Computer_Contact_Information: Network_Address: Network_Resource_Name: http://pubs.usgs.gov/sim/3123 Metadata_Reference_Information: Metadata_Date: 20120606 Metadata_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey Contact_Person: Joel E. Robinson Contact_Position: Geologist Contact_Address: Address_Type: mailing address Address: 345 Middlefield Road Address: MS 910 City: Menlo Park State_or_Province: California Postal_Code: 94025 Country: USA Contact_Voice_Telephone: (650)329-5322 Contact_Electronic_Mail_Address: jrobins@usgs.gov Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata Metadata_Standard_Version: FGDC-STD-001-1998 Metadata_Time_Convention: local time Metadata_Extensions: Online_Linkage: http://www.esri.com/metadata/esriprof80.html Profile_Name: ESRI Metadata Profile