Identification_Information: Citation: Citation_Information: Originator: U.S. Geological Survey Publication_Date: Unknown Title: Aeromagnetic and gravity data of the Central Transantarctic Mountains Series_Information: Series_Name: U.S. Geological Survey Open-File Report Issue_Identification: OFR 06-1255 Publication_Information: Publication_Place: Denver, CO Publisher: U. S. Geological Survey Description: Abstract: Near complete coverage of the East Antarctic Shield by ice hampers geological study of crustal architecture important for understanding global tectonic and climate history. Limited exposures in the central Transantarctic Mountains (CTAM), however, show that Archean and Proterozoic rocks of the shield as well as Neoproterozoic-lower Paleozoic sedimentary successions were involved in oblique convergence associated with Gondwana amalgamation. Subsequently, the area was overprinted by Jurassic magmatism and Cenozoic uplift. To extend the known geology of the region to ice-covered areas, we conducted an aeromagnetic survey flown in draped mode by helicopters over the Central Transantarctic Mountains and by fixed-wing aircraft over the adjacent polar plateau. We flew more than 32,000 line km covering an area of nearly 60,000 km2 at an average altitude of 600 m, with average line spacing 2.5 km over most areas and 1.25 km over basement rocks exposed in the Miller and Geologists ranges. Additional lines flown to the north, south, and west extended preliminary coverage and tied with existing surveys. Gravity data was collected on the ground along a central transect of the helicopter survey area. Purpose: From December 2003 to January 2004, the CTAM group flew a helicopter and twin-otter aeromagnetic survey and collected ground gravity station data along a profile. These data will be integrated with other geologic and geophysical data in order to extend the known geology of the region to ice-covered areas. Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: unknown Time_of_Day: unknown Currentness_Reference: publication date Status: Progress: Complete Maintenance_and_Update_Frequency: As needed Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: 139.275383 East_Bounding_Coordinate: 170.218440 North_Bounding_Coordinate: -82.357327 South_Bounding_Coordinate: -83.952338 Keywords: Theme: Theme_Keyword_Thesaurus: none Theme_Keyword: Gravity Theme_Keyword: Magnetic Anomalies Theme_Keyword: Magnetic Field Theme_Keyword: Magnetic Intensity Theme_Keyword: Tectonic Landforms Theme_Keyword: Tectonic Processes Theme: Theme_Keyword_Thesaurus: none Theme_Keyword: Transantarctic Mountains Theme_Keyword: TAM Theme_Keyword: geophysical data Theme_Keyword: aeromagnetic data Theme_Keyword: aeromagnetic grid Theme_Keyword: gravity data Theme: Theme_Keyword_Thesaurus: none Theme_Keyword: English Place: Place_Keyword_Thesaurus: none Place_Keyword: Antarctica Place_Keyword: Transantarctic Mountains Access_Constraints: None Use_Constraints: None. Acknowledgement of the U.S. Geological Survey (USGS), German Federal Institute for Geosciences and Natural Resources (BGR), and the National Science Foundation would be appreciated in products derived from these data. Point_of_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Eric D. Anderson Contact_Organization: U. S. Geological Survey Contact_Position: Geologist Contact_Address: Address_Type: mailing address Address: U.S. Geological Survey Address: Box 25046 Mail Stop 964 Address: Denver Federal Center City: Denver State_or_Province: Colorado 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 Data_Set_Credit: This project was funded by the National Science Foundation, Grant No. 0232042 and was in collaboration with scientists from the U. S. Geological Survey (USGS), German Federal Institute for Geosciences and Natural Resources (BGR) and University of Minnesota, Duluth. Native_Data_Set_Environment: Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 1; ESRI ArcCatalog 9.0.0.535 Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: The data in this file have been processed using various formulas and methods that are not usually documented but that represent industry standard practices for airborne data reduction. Logical_Consistency_Report: The data in this file were collected by a single contractor or group (CTAM) who were responsible for collecting and processing the data. The data from this survey were collected using the same instruments (magnetometers and navigational systems) throughout the survey and were collected in a normal length of time with no long delays between survey beginning and end. Standard industry practices of the time were followed in data collection and processing. A magnetic base station centrally located relative to the survey was established on ice close to Moody Nunatak which recorded the daily variations of Earth's magnetic field for removal from the total-field observed from the airborne instrument. The position of a cesium magnetometer carried in a bird slung ~30 m below the helicopter was accomplished with Trimble 4000 GPS and Ashtech Surveyor 12 receivers. The data from each flight were quality controlled. The crew for the aeromagnetic survey consisted of 4 helicopter pilots, 2 helicopter mechanics, 2 twin-otter pilots, 1 twin-otter mechanic, 6 scientists (geophysicist, geologists and engineers), a mountaineer and various camp operations staff. Completeness_Report: Loss of data due to poor transmission, channel dropout, obvious spiking, missing channels, and other obvious errors were replaced with a null value and subsequently interpolated. Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: Flight Path Recovery - High-resolution horizontal position of the survey aircraft used to collect data were determined from Global Positioning System (GPS) satellites. Positioning data were recorded in-flight independently using a Trimble GPS receiver. For some flights a differential position was calculated. For the rest of the flights an autonomous position was used. Quantitative_Horizontal_Positional_Accuracy_Assessment: Horizontal_Positional_Accuracy_Value: 20 m Horizontal_Positional_Accuracy_Explanation: Good to one meter when differentially corrected. Good to 20 meters when autonomous position was used. Vertical_Positional_Accuracy: Vertical_Positional_Accuracy_Report: Flight Path Recovery - High-resolution horizontal positions of the survey aircraft used to collect data were determined from Global Positioning System (GPS) satellites. Positioning data were recorded in-flight independently using a Trimble GPS and Ashtech Surveyor 12 receiver. For some flights a differential position was calculated. For the rest of the flights an autonomous position was used. The magnetometer was hung below the aircraft using a cable. This data set was collected as a draped survey having average terrain clearance of 600 m. Because aircraft, especially airplanes, cannot safely maintain a constant terrain clearance, error in vertical position is introduced. Quantitative_Vertical_Positional_Accuracy_Assessment: Vertical_Positional_Accuracy_Value: 20 m Vertical_Positional_Accuracy_Explanation: Good to one meter when differentially corrected. Good to 20 meters when autonomous position was used. Lineage: Process_Step: Process_Description: USGS and BGR personnel used the Geosoft software package Oasis Montaj version 5.1.6 to process the data. Standard quality control (QC) procedures were administered. Latitude, longitude and magnetic values were checked for obvious errors or spikes and null values were assigned to such. These points were then assigned values through linear interpolation. Horizontal positions were converted to a Lambert Conformal Conic projection described under spatial reference. Vertical positions recorded by the GPS unit were converted from orthometric elevation to ellipsoid height by adding the geoid model to the orthometric elevation recorded in the receiver. During helicopter operations two separate systems were flown simultaneously. One was controlled by the USGS and the other by the BGR. QC checks were performed by both groups. The individual datasets were then merged into a composite dataset where diurnal corrections and IGRF removal were performed, as well as tie-line and microleveling adjustments computed using standard Geosoft procedures with slight modifications to the microleveling amplitude cutoff. Process_Date: Unknown Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Planar: Map_Projection: Map_Projection_Name: Lambert Conformal Conic Lambert_Conformal_Conic: Standard_Parallel: -83.650000 Standard_Parallel: -82.850000 Longitude_of_Central_Meridian: 154.500000 Latitude_of_Projection_Origin: -83.250000 False_Easting: 300000.000000 False_Northing: 175000.000000 Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: coordinate pair Coordinate_Representation: Abscissa_Resolution: 625.000000 Ordinate_Resolution: 625.000000 Planar_Distance_Units: meters Geodetic_Model: Horizontal_Datum_Name: WGS_84 Ellipsoid_Name: WGS_84 Semi-major_Axis: 6378137.000000 Denominator_of_Flattening_Ratio: 298.257224 Entity_and_Attribute_Information: Detailed_Description: Entity_Type: Entity_Type_Label: Longitude Entity_Type_Definition: Longitude WGS84 Entity_Type_Definition_Source: self evident Attribute: Attribute_Definition: Longitude WGS84 Attribute_Definition_Source: self evident Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 128.745892093 Range_Domain_Maximum: 169.69225 Attribute_Units_of_Measure: decimal degrees Detailed_Description: Entity_Type: Entity_Type_Label: Latitude Entity_Type_Definition: Latitude WGS84 Entity_Type_Definition_Source: self evident Attribute: Attribute_Definition: Latitude WGS84 Attribute_Definition_Source: self evident Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: -87.117223185 Range_Domain_Maximum: -79.920871861 Attribute_Units_of_Measure: decimal degrees Detailed_Description: Entity_Type: Entity_Type_Label: x Entity_Type_Definition: Lambert Conformal Conic (2SP) Lat1 -82.85, Lat2 -83.65, LatO -83.25, LongO 154.5, FE 300000, FN 175000, Datum and Ellipsoid WGS84, Local Datum Transform WGS84 Entity_Type_Definition_Source: self evident Attribute: Attribute_Definition: Lambert Conformal Conic (2SP) Lat1 -82.85, Lat2 -83.65, LatO -83.25, LongO 154.5, FE 300000, FN 175000, Datum and Ellipsoid WGS84, Local Datum Transform WGS84 Attribute_Definition_Source: self evident Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: -59328.1568922 Range_Domain_Maximum: 489059 Attribute_Units_of_Measure: meters Detailed_Description: Entity_Type: Entity_Type_Label: y Entity_Type_Definition: Lambert Conformal Conic (2SP) Lat1 -82.85, Lat2 -83.65, LatO -83.25, LongO 154.5, FE 300000, FN 175000, Datum and Ellipsoid WGS84, Local Datum Transform WGS84 Entity_Type_Definition_Source: self evident Attribute: Attribute_Definition: Lambert Conformal Conic (2SP) Lat1 -82.85, Lat2 -83.65, LatO -83.25, LongO 154.5, FE 300000, FN 175000, Datum and Ellipsoid WGS84, Local Datum Transform WGS84 Attribute_Definition_Source: self evident Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: -257437.864195 Range_Domain_Maximum: 539567.4249843 Attribute_Units_of_Measure: meters Detailed_Description: Entity_Type: Entity_Type_Label: ellipsoid_elv Entity_Type_Definition: height of WGS84 ellipsoid Entity_Type_Definition_Source: self evident Attribute: Attribute_Definition: height of WGS84 ellipsoid Attribute_Definition_Source: self evident Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 185.86 Range_Domain_Maximum: 4680.8 Attribute_Units_of_Measure: meters Detailed_Description: Entity_Type: Entity_Type_Label: DATE Entity_Type_Definition: date Entity_Type_Definition_Source: self evident Attribute: Attribute_Definition: date Attribute_Definition_Source: self evident Attribute_Domain_Values: Unrepresentable_Domain: compound Detailed_Description: Entity_Type: Entity_Type_Label: UTC Entity_Type_Definition: Universal Time Coordinated Entity_Type_Definition_Source: self evident Attribute: Attribute_Definition: Universal Time Attribute_Definition_Source: self evident Attribute_Domain_Values: Unrepresentable_Domain: compound Detailed_Description: Entity_Type: Entity_Type_Label: mag_field Entity_Type_Definition: total magnetic field Entity_Type_Definition_Source: self evident Attribute: Attribute_Definition: Despiked total magnetic field Attribute_Definition_Source: self evident Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 57567.78 Range_Domain_Maximum: 61912.346 Attribute_Units_of_Measure: nanotesla (nT) Detailed_Description: Entity_Type: Entity_Type_Label: mag_field_lp Entity_Type_Definition: despiked total magnetic field with low pass filter applied Entity_Type_Definition_Source: self evident Attribute: Attribute_Definition: despiked total magnetic field with low pass filter applied Attribute_Definition_Source: self evident Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 57567.78 Range_Domain_Maximum: 61912.346 Attribute_Units_of_Measure: nanotesla (nT) Detailed_Description: Entity_Type: Entity_Type_Label: base_station_raw Entity_Type_Definition: raw base station values Entity_Type_Definition_Source: self evident Attribute: Attribute_Definition: raw base station values Attribute_Definition_Source: self evident Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 60159.3 Range_Domain_Maximum: 60895.99796667 Attribute_Units_of_Measure: nanotesla (nT) Detailed_Description: Entity_Type: Entity_Type_Label: base_station_sm Entity_Type_Definition: base station values smoothed by removing dropouts and linearly interpolating with a spline filter Entity_Type_Definition_Source: self evident Attribute: Attribute_Definition: base station values smoothed by removing dropouts and linearly interpolating with a spline filter Attribute_Definition_Source: self evident Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 60174.86 Range_Domain_Maximum: 60839.99998667 Attribute_Units_of_Measure: nanotesla (nT) Detailed_Description: Entity_Type: Entity_Type_Label: diurnal_raw Entity_Type_Definition: mag_field_lp diurnally corrected with raw base station data (60340-base_station+mag_field_lp, where 60340 represents an average base station value) Entity_Type_Definition_Source: self evident Attribute: Attribute_Definition: mag_field_lp diurnally corrected with raw base station data (60340-base_station)+mag_field_lp) Attribute_Definition_Source: self evident Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 57616.40903 Range_Domain_Maximum: 61859.546 Attribute_Units_of_Measure: nanotesla (nT) Detailed_Description: Entity_Type: Entity_Type_Label: diurnal_sm Entity_Type_Definition: Mag_field_lp diurnally corrected with smoothed base station data (60340-base_station+mag_field_lp, where 60340 represents an average base station value) Entity_Type_Definition_Source: self evident Attribute: Attribute_Definition: Mag_field_lp diurnally corrected with smoothed base station data (60340-base_station+mag_field_lp) Attribute_Definition_Source: self evident Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 57617.16588333 Range_Domain_Maximum: 61858.00126783 Attribute_Units_of_Measure: nanotesla (nT) Detailed_Description: Entity_Type: Entity_Type_Label: IGRF Entity_Type_Definition: International Geomagnetic Reference Field for 10th January 2004 - Model year 2000 Entity_Type_Definition_Source: self evident Attribute: Attribute_Definition: International Geomagnetic Reference Field for 10th January 2004 - Model year 2000 Attribute_Definition_Source: self evident Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 57681.96597918 Range_Domain_Maximum: 62044.81844907 Attribute_Units_of_Measure: nanotesla (nT) Detailed_Description: Entity_Type: Entity_Type_Label: mag_final_sm Entity_Type_Definition: final residual mag with smoothed base station and IGRF removed (diurnal_sm-IGRF+60340, where 60340 represents an average base station value) Entity_Type_Definition_Source: self evident Attribute: Attribute_Definition: final residual mag with smoothed base station and IGRF removed (diurnal_sm-IGRF+60340) Attribute_Definition_Source: self evident Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 60002.19268013 Range_Domain_Maximum: 61041.48901929 Attribute_Units_of_Measure: nanotesla (nT) Detailed_Description: Entity_Type: Entity_Type_Label: residual Entity_Type_Definition: Anomalous magnetic field (mag_final_sm-60340, where 60340 represents an average base station value) Entity_Type_Definition_Source: self evident Attribute: Attribute_Definition: Anomalous magnetic field (mag_final_sm-60340) Attribute_Definition_Source: self evident Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: -337.807319871 Range_Domain_Maximum: 701.4890192911 Attribute_Units_of_Measure: nanotesla (nT) Detailed_Description: Entity_Type: Entity_Type_Label: leveled Entity_Type_Definition: Anomalous magnetic field tie-line leveled using standard defaults with Geosoft software and microleveled using an amplitude of 10 nT as cutoff Entity_Type_Definition_Source: self evident Attribute: Attribute_Definition: Anomalous magnetic field tie-line leveled using standard defaults with Geosoft software and microleveled using an amplitude of 10 nT as cutoff Attribute_Definition_Source: self evident Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: -315.693289269 Range_Domain_Maximum: 576.1396095226 Attribute_Units_of_Measure: nanotesla (nT) Overview_Description: Entity_and_Attribute_Overview: Each record contains the following 17 attributes: Longitude - Longitude WGS84 - Decimal degrees Latitude - Latitude WGS84 - Decimal degrees x - Local x coordinate - meters y - Local y coordinate - meters ellipsoid_elv - WGS84 ellipsoid elevation - Meters Date - Date data was collected - YYYY/MM/DD Time - Time data was collected - hh:mm:ss.ss mag_field - Despiked magnetic field value - Nanotesla mag_field_lp - Despiked magnetic field value with a low pass filter applied to get rid of micropulsations caused by instrumentation - Nanotesla base_station_raw - raw base station value - Nanotesla base_station_sm - smoothed base station value - Nanotesla diurnal_raw - diurnal correction applied to mag_field_lp using raw base station values - Nanotesla diurnal_smooth - diurnal correction applied to mag_field_lp using smoothed base station values - Nanotesla IGRF - IGRF correction model 2000 - Nanotesla mag_final_sm - final mag with smoothed base station - Nanotesla residual - anomalous magnetic field - Nanotesla leveled - final leveled data - both tie-line and microleveling techniques applied - Nanotesla Because the magnetic field of the earth varies diurnally, a stationary base magnetometer is maintained on the ground during airborne surveying. The base magnetometer records changes in the magnetic field (in nanoTeslas) as a function of time. The magnetic changes may have an amplitude of 20 to 50 nanoTeslas. If changes are more severe, as would occur from a magnetic storm, surveying is discontinued or the data recorded are not used. Diurnal variations are then removed from the airborne magnetic data based on the common time. The airborne magnetometer is accurate to about 0.002 nanotesla (nT) at 1 Hz and 0.02 nT at 10 Hz, and the base magnetometer has an accuracy of 1 nT. The accuracy of the base-corrected airborne value therefore is near 1 nanoTeslas or better. The total magnetic value is the despiked, diurnally-corrected magnetic field minus a geomagnetic reference field (GRF), which is a long-wavelength regional magnetic field. The most commonly used reference field is determined from a model developed by the International Association of Geomagnetism and Aeronomy (IAGA). The International Geomagnetic Reference Field (IGRF) is a predictive model adopted at the beginning of a model period (e.g. in 1989 for 1990-1995). After the model period, a revised definitive model is adopted, the Definitive Geomagnetic Reference Field (DGRF). This is the preferred model to use for removing regional magnetic fields. The temporal variations cannot be completely predicted, thus error arises in the application of the IGRF reductions. These errors cannot be evaluated until the release of the DGRF, a minimum of five years after the IGRF release. This field is issued to best describe the configuration of the earth's past magnetic field. For this survey, the field removed was the IGRF model 2000. Entity_and_Attribute_Detail_Citation: Nettleton, L.L., 1971, Elementary Gravity and Magnetics for Geologists and Seismologists: Society of Exploration Geophysicists Monograph Series No. 1, p. 83-87. Dobrin, M.B., 1976, Introduction to Geophysical Prospecting: New York, McGraw-Hill Book Company, p. 505-517. Distribution_Information: Distributor: Contact_Information: Contact_Person_Primary: Contact_Person: Eric D. Anderson Contact_Organization: U. S. Geological Survey Contact_Position: Geologist Contact_Address: Address_Type: mailing address Address: U.S. Geological Survey Address: Box 25046 Mail Stop 964 Address: Denver Federal Center 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 Resource_Description: Downloadable Data Distribution_Liability: Although all data published on this website have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Metadata_Reference_Information: Metadata_Date: 20050204 Metadata_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Eric D. Anderson Contact_Organization: U. S. Geological Survey Contact_Position: Geologist Contact_Address: Address_Type: mailing address Address: U.S. Geological Survey Address: Box 25046 Mail Stop 964 Address: Denver Federal Center 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 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