Identification_Information: Citation: Citation_Information: Originator: R.C. Jachens Originator: V.E. Langenheim Publication_Date: 2014 Title: Gravity survey and depth to basement of Fort Irwin Military Reservation, Mojave Desert, California Geospatial_Data_Presentation_Form: point digital data Series_Information: Series_Name: Open-File Report Issue_Identification: 2013-1024–H Publication_Information: Publication_Place: Menlo Park, CA Publisher: U.S. Geological Survey Online Linkage: http://pubs.usgs.gov/of/2013/1024/h/ Description: Abstract: Gravity data over the Fort Irwin Military Reservation, Mojave Desert, California were analyzed in conjunction with geologic information, well logs, and electrical soundings to produce a gridded dataset of the estimated depth to pre-Cenozoic basement which served as the basis for producing contours of the depth to pre-Cenozoic basement rock. Digital Files: an ASCII file containing gridded values and geographic locations of the Isostatic Residual Gravity Anomaly and an ASCII file containing values and geographic locations of the the depth to basement of the Fort Irwin Military Reservation, Mojave Desert, California. This metadata file describes the gridded depth to basement data. Purpose: The depth to basement map identifies basinal features of importance for analyzing the hydrogeologic framework of the Fort Irwin Military Reservation. Supplemental_Information: This database contains values and locations of depth to basement inferred from gravity and other data originally presented in smaller scale format, including detailed gravity data collected by the US Geological Survey. Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 2011 Ending_Date: 2012 Currentness_Reference: publication date Status: Progress: Complete Maintenance_and_Update_Frequency: None planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -117.3 East_Bounding_Coordinate: -116.2 North_Bounding_Coordinate: 35.9 South_Bounding_Coordinate: 34.7 Keywords: Theme: Theme_Keyword: gravity Theme_Keyword: isostatic residual gravity grid anomaly Theme_Keyword: depth to basement Place: Place_Keyword: southern California Place_Keyword: Mojave Desert Place_Keyword: Fort Irwin Access_Constraints: none Use_Constraints: Uses of this digital data should not violate the spatial or attribute resolution of the data. Although the digital form of the data stores location and attribute values to several decimals of precision, the data are subject to the accuracy and precision inherent in the data due to data collection and processing limitations. Where these data are used in combination with other data, the precision and accuracy of the resulting dataset is limited by the precision and accuracy of the input datasets. Acknowledgement of the U.S. Geological Survey is appreciated for products derived from these data. Point_of_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Robert Jachens Contact_Organization: U.S. Geological Survey Contact_Position: geophysicist Contact_Address: Address_Type: physical address Address: 345 Middlefield Rd. City: Menlo Park State_or_Province: CA Postal_Code: 94025 Country: USA Contact_Voice_Telephone: 650-329-5300 Contact_Electronic_Mail_Address: jachens@usgs.gov Native_Data_Set_Environment: Earth Vision Surface Display Library Native_Data_Set_Environment: Geophysical data were stored and analyzed on a SUN Ultra4000 UNIX platform Geospatial_Data_Presentation_Form: ascii digital data (gridded depth to basement data) Series_Information: Series_Name: U.S. Geological Survey (USGS) Open-File Report Issue_Identification: 2012-XXXX Publication_Information: Publication_Place: Menlo Park, California Publisher: U.S. Geological Survey Online_Linkage: Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: gridded depth to basement values are reported to 0.0001 km Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: accuracy should be within 250 meters (grid cell size) Lineage: Process_Step: Process_Description: Data from detailed gravity surveys were interpolated to a rectangular grid with nodes spaced 250 m apart using a minimum curvature algorithm (Briggs, 1974) using a Transverse Mercator projection (central meridian -117.0, base latitude 0.0, scale factor 0.9996). These gridded data were analyzed to yield an inferred depth to pre-Cenozoic basement grid. Process_Date: 2012 Spatial_Data_Organization_Information: Direct_Spatial_Reference_Method: Point Point_and_Vector_Object_Information: SDTS_Terms_Description: SDTS_Point_and_Vector_Object_Type: Entity point Point_and_Vector_Object_Count: 234450 Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Geographic: Latitude_Resolution: 0.0001 Longitude_Resolution: 0.0001 Geographic_Coordinate_Units: Decimal degrees Geodetic_Model: Horizontal_Datum_Name: North American Datum of 1929 Ellipsoid_Name: Clarke 1866 Entity_and_Attribute_Information: Detailed_Description: Entity_Type: Entity_Type_Label: depth2basement.txt Attribute: Attribute_Label: depth to basement Attribute_Definition: gridded depth to pre-Cenozoic basement Attribute: Attribute_Label: lon_nad27 Attribute_Definition: longitude coordinate Attribute_Value_Accuracy_Information: Attribute_Value_Accuracy: 250 m Attribute: Attribute_Label: lat_nad27 Attribute_Definition: latitude coordinate Attribute_Value_Accuracy_Information: Attribute_Value_Accuracy: 250 m Distribution_Information: Distributor: U.S. Geological Survey Resource_Description: Downloadable Data Standard_Order_Process: Digital_Form: Digital_Transfer_Information: Format_Name: ASCII Transfer_Size: 10081350 Network_Resource_Name: http://pubs.usgs.gov/of/2012/XXXX Process_Date: 2011-2012 Process_Step: Process_Description: Geophysical mapping The gridded depth values are derived from an analysis of the newly collected gravity data (this report) and previously published gravity data, in conjunction with geologic information, well data, and electrical soundings. The gravity data were compiled from existing publications (Pan-American Center for Earth and Environmental Studies, 2010; Snyder and others, 1982) and the data were interpolated to a regular grid (Briggs, 1974) with cell dimensions of 250 m in both the X and Y directions. These data were analyzed by the method of Jachens and Moring (1990) to yield an inferred depth to basement grid. Briggs, I., 1974, Machine contouring using minimum curvature: Geophysics, v. 39, no. 1, p. 39-48. Jachens, R.C., and Moring, B.C., 1990, Maps of thickness of Cenozoic deposits and the isostatic residual gravity over basement for Nevada: U.S. Geological Survey Open-File Report 90-404, scale 1:1,000,000. Pan-American Center for Earth and Environmental Studies, 2010, Gravity database, http://irpsvgis00.utep.edu/repositorywebsite, last accessed January 8, 2010. Snyder, D.B., Roberts, C.W., Saltus, R.W., and Sikora, R.F., 1982, A magnetic tape containing the principal facts of 64,026 gravity stations in the state of California: available from National Technical Information Service, U.S. Department of Commerce, Springfield, VA 22152, PB 82-168287 [description of magnetic tape, PB 82-168279], magnetic tape, 34 p. Metadata_Reference_Information: Metadata_Date: 20120724 Metadata_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Robert Jachens Contact_Organization: U.S. Geological Survey Contact_Position: geophysicist Contact_Address: Address_Type: mailing and physical address Address: 345 Middlefield Rd. City: Menlo Park State_or_Province: CA Postal_Code: 94025 Contact_Voice_Telephone: 650-329-5300 Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata Metadata_Standard_Version: FGDC-STD-001-1998 Metadata_Time_Convention: local time Metadata_Extensions: