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Magnetic Anomaly Map of North America

Introduction

The Geological Survey of Canada, U.S. Geological Survey, and Consejo de Recursos Minerales of Mexico have compiled aeromagnetic data to produce a database and digital map for the North American continent. The unified data set is a powerful tool for determining structure, geologic processes, and tectonic evolution of the continent and can be used to help resolve societal and scientific investigations that span national boundaries.

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North American Magnetic Anomaly Map

Outline of North American continent with identifiers for Canadian, U.S., and Mexican participating agencies.

The digital magnetic anomaly database and map for the North American continent is the result of a joint effort by the Geological Survey of Canada (GSC), U.S. Geological Survey (USGS), and Consejo de Recursos Minerales of Mexico (CRM). This integrated, readily accessible, modern digital database of magnetic anomaly data is a powerful tool for further evaluation of the structure, geologic processes, and tectonic evolution of the continent and may also be used to help resolve societal and scientific issues that span national boundaries. The North American magnetic anomaly map derived from the digital database provides a comprehensive magnetic view of continental-scale trends not available in individual data sets, helps link widely separated areas of outcrop, and unifies disparate geologic studies.

The group created three unique, gridded data sets used to make the magnetic anomaly map of North America. Details on the data processing and compilation procedures used to produce the grids are described in the booklet that accompanies the North American magnetic anomaly map. The first grid shows the magnetic field at 305 meters above terrain. For the second grid we removed long-wavelength anomalies (500 km and greater) from the first grid. This grid was used for the published map. The third grid uses an equivalent source method, based on long-wavelength characterization using satellite data, to correct for spurious shifts in the original magnetic anomaly grid. Further details on the grids are described in the open-file report listed below.

North American Magnetic Anomaly Group (NAMAG)

  • Viki Bankey
  • Alejandro Cuevas
  • David Daniels
  • Carol A. Finn
  • Israel Hernandez
  • Patricia Hill
  • Robert Kucks
  • Warner Miles
  • Mark Piulkington
  • Carter Roberts
  • Walter Roest
  • Victoria Rystrom
  • Sarah Shearer
  • Stephen Snyder
  • Ronald Sweeney
  • Julio Velez

Products for the North American Magnetic Anomaly Database and Grids

Map and Booklet

Outline of North American continent with identifiers for Canadian, U.S., and Mexican participating agencies.

Available at: http://pubs.usgs.gov/sm/mag_map/

Gridded Data

Available at: USGS Open-File Report 2002-414 Digital data grids for the magnetic anomaly map of North America, available at https://pubs.usgs.gov/of/2002/ofr-02-414/.

Interactive Geospatial Data for the Map

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United States

Index Map of United States

The initial compilation of magnetic data for the United States is based on state and regional composite grids. These data were regridded to an interval of 1 km and reprojected for the North American compilation.

Airborne Geophysical Survey Data By State

index map of United States

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DNAG: Decade of North American Geology

In the early 1980's, the USGS spearheaded the first effort to produce a magnetic map for the United States (Zietz, 1982). Although this map was assembled entirely in analog form, it represented the first qualitative view of continental-scale features. A digitized version of this map constitutes most of the data for the conterminous United States in the 1987 Magnetic Anomaly Map of North America (Committee for the Magnetic-Anomaly Map of North America, 1987), constructed as part of the Geological Society of America's Decade of North American Geology (DNAG) program.

Reference: Zietz, I., 1982, Composite magnetic anomaly map of the United States; Part A, Conterminous United States: U.S. Geological Survey Investigations Map GP-954-A, 59 p., 2 sheets, scale 1:2,500,000, https://pubs.er.usgs.gov/publication/gp954A.

DNAG Magnetic Anomaly of North America

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U.S. Digital Data

After pioneering the first airborne magnetic survey in 1944, the U.S. Geological Survey (USGS) has collected piecemeal aeromagnetic data for most of the U.S., including offshore areas on both coasts. The U.S. Geological Survey's digital and analog archives comprise more than 1,000 surveys, covering approximately 8,000,000 line-km of data, flown at various flight heights and line spacings.

The following open-file reports contain the United States aeromagnetic data sets. The duplication of the surveys included in the two reports is minimal.

Digital Data

The data available here are the currently available digitally standardized magnetic databases, metadata reports, and images of survey coverage and quality for individual aeromagnetic surveys.

Interactive geospatial portal for the magnetic anomaly maps and data and state gridded compilations.

U.S. Geological Survey and National Geophysical Data Center, 2002, Digital Aeromagnetic Datasets for the Conterminous United States and Hawaii - A Companion to the North American Magnetic Anomaly Map:, U.S. Geological Survey Open-File Report 02-361.

Connard, G.G., Saltus, R.W., Hill, P.L., Carlson, L., and Milicevic, B., 1999, Alaska Digital Aeromagnetic Database Description: U.S. Geological Survey Open-File Report 99-0503.

Digitized Analog Data

The data available here are digitally converted analog magnetic field intensity maps. These maps are either USGS or publicly accessible publications. They were generated as needed to fulfill USGS requirements.

U.S. Geological Survey, 2000, Digitized Aeromagnetic Datasets for the Conterminous United States, Hawaii, and Puerto Rico: U.S. Geological Survey Open-File Report 99-0557.

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Case Studies from the North American Magnetic Database Compilation Project

Reports

The U.S. Geological Survey Open-File report listed below contains the following United States and Canadian projects that used the new North American magnetic data:

  • Mapping Precamiran basement in Alberta, Canada, by Mark Pilkington
  • Mapping Precambrian rift structures in the mid-continent, US, by William Cannon
  • Aeromagnetic Anomalies in Earthquake Hazard Investigations: An Example from the Canadian-U.S. Border, by Richard J. Blakely and Samuel Y. Johnson
  • Applications of aeromagnetic data to water and mineral resource problems along the Arizona-Sonara international border, by Mark E. Gettings
  • Marine Magnetic Anomalies in Labrador, by Walter Roest

Examples of the Utility of Magnetic Anomaly Data for Geologic Mapping

U.S. Geological Survey Open-File Report 02-0400
Edited By Carol A. Finn

With Sections By

  • Mark Pilkington, Geological Survey of Canada, Ottawa, Canada
  • Richard Blakely, USGS, Menlo Park, California
  • Samuel Johnson, Denver, Colorado
  • William Cannon, USGS, Reston, Virginia
  • Mark Gettings, USGS, Tucson, Arizona
  • Walter Roest, Geological Survey of Canada, Ottawa, Canada

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