Identification_Information: Citation: Citation_Information: Originator: U.S. Geological Survey Publication_Date: 2009 Title: High-resolution aeromagnetic survey to image shallow faults, Poncha Springs and vicinity, Chaffee County, Colorado Geospatial_Data_Presentation_Form: raster digital data Series_Information: Series_Name: U.S. Geological Survey Open-File Report Issue_Identification: Open-File Report 2009-1156 Publication_Information: Publication_Place: Denver, Colo., USA Publisher: U.S. Geological Survey Description: Abstract: High-resolution aeromagnetic data were acquired over the town of Poncha Springs and areas to the northwest to image faults, especially where they are concealed. Because this area has known hot springs, faults or fault intersections at depth can provide pathways for upward migration of geothermal fluids or concentrate fracturing that enhances permeability. Thus, mapping concealed faults provides a focus for follow-up geothermal studies. Fault interpretation was accomplished by synthesizing interpretative maps derived from several different analytical methods, along with preliminary depth estimates. Faults were interpreted along linear aeromagnetic anomalies and breaks in anomaly patterns. Many linear features correspond to topographic features, such as drainages. A few of these are inferred to be fault- related. The interpreted faults show an overall pattern of criss- crossing fault zones, some of which appear to step over where they cross. Faults mapped by geologists suggest similar crossing patterns in exposed rocks along the mountain front. In low-lying areas, interpreted faults show zones of west-northwest-, north-, and northwest- striking faults that cross ~3 km (~2 mi) west-northwest of the town of Poncha Springs. More easterly striking faults extend east from this juncture. The associated aeromagnetic anomalies are likely caused by magnetic contrasts associated with faulted sediments that are concealed less than 200 m (656 ft) below the valley floor. The faults may involve basement rocks at greater depth as well. A relatively shallow (<300 m or <984 ft), faulted basement block is indicated under basin-fill sediments just north of the hot springs and south of the town of Poncha Springs. Purpose: The overall objective of the survey is to map concealed faults that may be related to geothermal resources, such as hot springs. Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 2008 Ending_Date: 2009 Currentness_Reference: publication date Status: Progress: complete Maintenance_and_Update_Frequency: none planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -106.25 degrees W. longitude East_Bounding_Coordinate: -106.0 degrees W. longitude North_Bounding_Coordinate: 38.65 degrees N. latitude South_Bounding_Coordinate: 38.4 degrees N. latitude Keywords: Place: Place_Keyword_Thesaurus: none Place_Keyword: United States Place_Keyword: Colorado Place_Keyword: Poncha Springs Place_Keyword: Upper Arkansas Valley Theme: Theme_Keyword_Thesaurus: none Theme_Keyword: aeromagnetic data Theme_Keyword: geophysical data Theme_Keyword: geophysical model Access_Constraints: none Use_Constraints: none Point_of_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: V.J.S. Grauch Contact_Organization: U.S. Geological Survey Contact_Address: Address_Type: mailing address Address: Box 25046, MS964 Denver Federal Center City: Denver State_or_Province: CO Postal_Code: 80225-0046 Country: USA Contact_Voice_Telephone: 303-236-1393 Contact_Electronic_Mail_Address: tien@usgs.gov Data_Set_Credit: V.J.S. Grauch B.J. Drenth Native_Data_Set_Environment: These files were created using the following proprietary software: ER Mapper, from ERDAS; Oasis Montaj, from Geosoft, Inc.; and ArcGIS from ESRI Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: These files represent interpretations derived from analysis of grids of magnetic values that represent the total intensity of the Earth's magnetic field after removal of the International Geomagnetic Reference Field (IGRF). The original data is documented in U.S. Geological Survey Open-File Report 2009-1089. Judgments and limitations involved in the interpretation are described in the report that accompanies these files. Logical_Consistency_Report: Geophysical analysis follows established approaches that are documented in the report that accompanies these files. Completeness_Report: Interpretations are complete for the area covered, but are always subject to change as a result of future work. Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: These data are based on modelled criteria. The horizontal position, therefore, is only as accurate as the underlying presumptions of physical properties on which they are based. The data are a modelled interpretation that is based on various original data that are described more fully in the original report. A higher degree of uncertainty in the interpretation is indicated by the filenames that contain the word "proposed". Vertical_Positional_Accuracy: Vertical_Positional_Accuracy_Report: These data are based on modelled criteria. The vertical position, therefore, is only as accurate as the underlying presumptions of physical properties on which they are based. The data are a modelled interpretation that is based on various original data that are described more fully in the original report. A higher degree of uncertainty in the interpretation is indicated by the filenames that contain the word "proposed". Lineage: Process_Step: Process_Description: Locating faults using geophysical interpretation requires a variety of approaches. The final inter- pretations take the form of lines on a map. This complex process is described in the report that accompanies these files. Process_Date: 2009 Spatial_Data_Organization_Information: Direct_Spatial_Reference_Method: vector Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Planar: Map_Projection: Map_Projection_Name: Universal Transverse Mercator Transverse_Mercator: Scale_Factor_at_Central_Meridian: 0.9996 Longitude_of_Central_Meridian: -105.0 Latitude_of_Projection_Origin: 0.0 False_Easting: 500,000 m False_Northing: 0 Geodetic_Model: Horizontal_Datum_Name: North American Datum of 1983 Ellipsoid_Name: sphere Semi-major_Axis: 6378206.4 Denominator_of_Flattening_Ratio: 0.926 Geodetic_Model: Horizontal_Datum_Name: North American Datum of 1927 Ellipsoid_Name: sphere Semi-major_Axis: 6378206.4 Denominator_of_Flattening_Ratio: 0.926 Entity_and_Attribute_Information: Overview_Description: Entity_and_Attribute_Overview: Files are in Arc/Info shape file format, which consists of several associated files having the same prefix and various suffixes. Together, these files form a vector coverage. Suffixes: .dbf (database file) .prj (projection file) .shp (shape definition file) .shx (shape entities) Coverages: psmagflts.*** - Vector file of lines representing faults interpreted from magnetic data. Horizontal datum name: North American Datum of 1983 psmagflts_proposed.*** - Vector file of lines representing faults interpreted from magnetic data that are uncertain. Horizontal datum name: North American Datum of 1983 psmagfltsNAD27.*** - Vector file of lines representing faults interpreted from magnetic data. Horizontal datum name: North American Datum of 1927 psmagflts_proposedNAD27.*** - Vector file of lines representing faults interpreted from magnetic data that are uncertain. Horizontal datum name: North American Datum of 1927 Distribution_Information: Distributor: Contact_Information: Contact_Organization_Primary: Contact_Organization: USGS Information Services Contact_Address: Address_Type: mailing address Address: Box 25286, Building 810 Denver Federal Center City: Denver State_or_Province: CO Postal_Code: 80225 Country: USA Contact_Voice_Telephone: 303-202-4700 Contact_Electronic_Mail_Address: www.usgs.gov/pubprod Resource_Description: USGS Open-File Report OFR 2009-1156 Distribution_Liability: The act of distribution shall not constitute any warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Metadata_Reference_Information: Metadata_Date: 2009170 Metadata_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: V.J.S. Grauch Contact_Organization: U.S. Geological Survey Contact_Address: Address_Type: mailing address Address: U.S. Geological Survey Box 25046 Mail Stop 964 Denver Federal Center City: Denver State_or_Province: CO Postal_Code: 80225 Country: USA Contact_Voice_Telephone: 303-236-1393 Contact_Electronic_Mail_Address: tien@usgs.gov Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata Metadata_Standard_Version: FGDC-STD-001-1998