Identification_Information: Citation: Citation_Information: Originator: P.K. Sims Originator: J.M. O'Neill Originator: Viki Bankey Originator: E. Anderson Publication_Date: 2004 Title: Precambrian basement geologic map of Montana-An interpretation of aeromagnetic anomalies Edition: version 1.0 Geospatial_Data_Presentation_Form: map Series_Information: Series_Name: USGS Scientific Investigations Map Issue_Identification: Scientific Investigations Map 2829 Publication_Information: Publication_Place: Denver, Colorado, U.S.A. Publisher: United States Geological Survey Online_Linkage: http://pubs.usgs.gov/sim/2829 Description: Abstract: Newly compiled aeromagnetic anomaly data of Montana, in conjunction with the known geologic framework of basement rocks, have been combined to produce a new interpretive geologic basement map of Montana. Crystalline basement rocks compose the basement, but are exposed only in the cores of mountain ranges in southwestern Montana. Principal features deduced from the map are: (1) A prominent northeast-trending, 200-km-wide zone of spaced negative anomalies, which extends more than 700 km from southwestern Montana's Beaverhead Mountains to the Canadian border and reflects suturing of the Archean Mexican Hat Block against the Archean Wyoming Province along the Paleoproterozoic Trans-Montana Orogen (new name) at about 1.9-1.8 Ga; (2) North-northwest-trending magnetic lows in northeastern Montana, which reflect the 1.9-1.8 Ga Trans-Hudson Orogen and truncate the older Trans-Montana Zone; and (3) Subtle northwest- and west-trending negative anomalies in central and western Montana, which represent the northernmost segment of brittle-ductile transcurrent faults of the newly recognized Mesoproterozoic Trans-Rocky Mountain fault system. Structures developed in the Proterozoic provided zones of crustal weakness reactivated during younger Proterozoic and Phanerozoic igneous and tectonic activity. For example, the Trans-Montana Zone guided basement involved thrust faulting in southwestern Montana during the Sevier Orogeny. The Boulder Batholith and associated ore deposits and the linear belt of alkaline intrusions to the northeast were localized along a zone of weakness between the Missouri River suture and the Dillon shear zone of the Trans-Montana Orogen. The northwest-trending faults of Trans-Rocky Mountain system outline depocenters for sedimentary rocks in the Belt Basin. This fault system provided zones of weakness that guided Laramide uplifts during basement crustal shortening. Northwest-trending zones have been locally reactivated during Neogene basin-range extension. Purpose: This ARC/INFO dataset was developed to provide a geologic map GIS database of the Precambrian basement of Montana for use in spatial analysis by a variety of users. Supplemental_Information: Coverages included in this geospatial database: faults2: line coverage of geologic faults rocks2: polygon coverage of geologic units and contacts mtpt: point coverage of symbols supr_grp2: polygon coverage of areas containing major bodies of Belt Supergroup (Yb) or Yellowjacket Formation (Yb) Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 2004 Currentness_Reference: publication date Status: Progress: Complete Maintenance_and_Update_Frequency: none currently planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -116.155203 East_Bounding_Coordinate: -103.640966 North_Bounding_Coordinate: 49.129673 South_Bounding_Coordinate: 44.248905 Keywords: Theme: Theme_Keyword_Thesaurus: American Geological Institute Glossary of Geology Theme_Keyword: aeromagnetic anomalies Theme_Keyword: Archean Theme_Keyword: basement Theme_Keyword: batholiths Theme_Keyword: intrusions Theme_Keyword: mapping Theme_Keyword: Montana Orogeny Theme_Keyword: tectonics Place: Place_Keyword_Thesaurus: Board of Geographic Names Place_Keyword: Montana Place_Keyword: Bitterroot Range Place_Keyword: Beaverhead Mountains Place_Keyword: Rocky Mountains Place_Keyword: Wyoming Access_Constraints: none Use_Constraints: none. Acknowledgment of the U.S. Geological Survey would be appreciated in products derived from these data. Point_of_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Eric Anderson Contact_Organization: U.S. Geological Survey Contact_Address: Address_Type: mailing address Address: MS 964, Box 25046 DFC City: Denver State_or_Province: CO Postal_Code: 80225-0046 Country: USA Contact_Voice_Telephone: 303-236-5652 Contact_Facsimile_Telephone: 303-236-1425 Contact_Electronic_Mail_Address: ericanderson@usgs.gov Browse_Graphic: Browse_Graphic_File_Name: http://pubs.usgs.gov/sim/2829/2829.pdf Browse_Graphic_File_Description: graphic representation of map layout Browse_Graphic_File_Type: PDF Data_Set_Credit: Eric Anderson, U.S. Geological Survey, served as GIS coordinator in the creation of the GIS database. Alex J. Donatich and Gregory G. Green, U.S. Geological Survey, assisted in proofing the geology and correcting the GIS database. Native_Data_Set_Environment: Microsoft Windows 2000 Version 5.0 (Build 2195) Service Pack 4 ESRI ArcCatalog 8.3.0.800; ARC/INFO version 8.3 Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: The database consists of newly generated data that were compiled on mylar and then digitized in ARC/INFO. . This map was thoroughly reviewed for conformity with U.S. Geological Survey editorial standards and stratigraphic nomenclature. Logical_Consistency_Report: Map elements were visually checked by the authors and editor for overshoots, undershoots, duplicate features, polygon attributes, and other errors. Automated (ARC/INFO) routines were also used to check the databases for polygon label errors and dangling arcs. The coverages were cleaned in ARC/INFO to ensure logical consistency that is topologically clean. The map was reviewed by other geologists for consistency with basic geologic principles and general conformity to USGS mapping standards. Completeness_Report: This dataset is complete and includes the spatial coverages pertaining to the geologic map. Lineage: Process_Step: Process_Description: Paul Sims compiled the geology. Eric Anderson digitized the geology. Gregory G. Green assisted in correcting the GIS database. The digital database was quality checked by Alex J. Donatich. The layout of the finished paper map was prepared by Alex J. Donatich and checked by Paul Sims. Process_Date: 2003-2004 Spatial_Data_Organization_Information: Direct_Spatial_Reference_Method: Vector Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Planar: Map_Projection: Map_Projection_Name: Lambert Conformal Conic Lambert_Conformal_Conic: Standard_Parallel: 33.000000 Standard_Parallel: 45.000000 Longitude_of_Central_Meridian: -110.000000 Latitude_of_Projection_Origin: 0.000000 False_Easting: 0.000000 False_Northing: 0.000000 Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: coordinate pair Coordinate_Representation: Abscissa_Resolution: 0.002048 Ordinate_Resolution: 0.002048 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 Entity_and_Attribute_Information: Overview_Description: Entity_and_Attribute_Overview: The data are supplied in ARC/INFO export format and ArcView shapefile format. >Attribution of user-defined item ARC_TYPE in faults2.aat: >strike-slip fault, certain >strike-slip fault, inferred >thrust fault (Laramide), certain >thrust fault (Paleoproterozoic), certain >thrust fault (Paleoproterozoic), inferred >thrust fault (Sevier), certain >Attribution of user-defined item ARC_TYPE in rocks2.aat: >contact coincident with fault >contact, certain >contact, inferred >map boundary >Attribution of user-defined item FORMATION in rocks2.pat: >Ag >Agn >Amh >Ats >Aum >Czv >VUs >Wg >Wgf >Wsc >XAr >Xfb >Xi >Xm >Xt >Xw >Xwv >Yb >Attribution of user-defined item EXPOSURE in rocks2.pat: >no [indicates that unit is not exposed] >yes [indicates that unit is exposed] >Attribution of user-defined item TYPE in mtpt.pat: >dip >drill hole >foliation >strike slip >Attribution of user-defined item SUPR_GRP in supr_grp.pat: >Yb >Yy Entity_and_Attribute_Detail_Citation: none Distribution_Information: Distributor: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey Contact_Address: Address_Type: mailing address Address: Central Publications Group Address: MS 902, Box 25046 Address: Denver Federal Center City: Denver State_or_Province: Colorado Postal_Code: 80225 Country: USA Contact_Voice_Telephone: (888)ASK-USGS Contact_Electronic_Mail_Address: webmaster@geology.cr.usgs.gov Distribution_Liability: The U.S. Geological Survey (USGS) provides these geographic data "as is". The USGS makes no guarantee or warranty concerning the accuracy of information contained in the geographic data. The USGS further makes no warranties, either expressed or implied, as to any other matter whatsoever, including, without limitation, the condition of the product, or its fitness for any particular purpose. The burden for determining fitness for use lies entirely with the user. Although these data have been processed successfully on computers at the USGS, no warranty, expressed or implied, is made by the USGS regarding the use of these data on any other system, nor does the fact of distribution constitute or imply any such warranty. Standard_Order_Process: Digital_Form: Digital_Transfer_Information: Format_Name: ArcInfo interchange file and ArcInfo shapefile formats Format_Version_Number: ArcInfo version 8.3 File_Decompression_Technique: .tar.gz - UNIX gzip-compressed TAR file - use GNU zip and TAR to extract .ZIP - Windows ZIP archive - use Winzip, PKZip, or similar to extract Digital_Transfer_Option: Online_Option: Computer_Contact_Information: Network_Address: Network_Resource_Name: Fees: None Distribution_Information: Distributor: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S.Geological Survey Contact_Address: Address_Type: mailing address Address: USGS Information Services Address: Box 25286 City: Denver State_or_Province: CO Postal_Code: 80225 Country: United States Contact_Voice_Telephone: 1-888-ASK-USGS Resource_Description: Scientific Investigations Map 2829 (plot-on-demand) Distribution_Liability: none Standard_Order_Process: Non-digital_Form: Available as one printed sheet. Order from USGS at the address listed above or see for more ordering information. Fees: For current prices please see Metadata_Reference_Information: Metadata_Date: 20040331 Metadata_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Eric Anderson Contact_Organization: U.S. Geological Survey Contact_Address: Address_Type: mailing address Address: Denver Federal Center, MS 964 Address: Box 25046 City: Denver State_or_Province: Colorado Postal_Code: 80225 Country: USA Contact_Voice_Telephone: (303) 236-5652 Contact_Electronic_Mail_Address: ericanderson@usgs.gov Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata Metadata_Standard_Version: FGDC-STD-001-1998 Metadata_Access_Constraints: None Metadata_Use_Constraints: None