Geologic, Bouguer Gravity Map and Magnetic Map of the Grand Banks and Flemish Cap

Steven Dutch, Professor Emeritus, Natural and Applied Sciences, Universityof Wisconsin - Green Bay

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Gravity and Magnetic Maps of the States

Geology with One-Degree Grid

Bathymetric contours at 1000, 2000, 3000 and 4000 m are shown in brown. This is why atlases need a complete set of maps at a single scale. Most people know there's a submerged extension of the continental shelf off Newfoundland. These maps make it clear it's the size of Arizona.  One pixel = 1 km

Topography

Bouguer Gravity Map

In addition to the Newfoundland coast, the 1000-m bathymetric contour is shown as an approximation to the edge of continental crust. Note how precisely it follows the boundaries of the gravity highs.

Magnetic Anomaly Map

Legend

Marine refers to well-stratified rocks mostly (but not entirely) ofmarine origin. Eugeo refers to eugeosynclinal rocks, that is, deep-watersedimentary rocks of continental slope or trench origin. Other headings areself-explanatory.

There are about 160 lithologic units on the Geologic Map of the United Statesby King and Beikman, counting units with metamorphic overprint. The 256 Colorson an 8-bit Color palette are more than enough to show these, but many of theColors are very hard to distinguish by eye. Colors were chosen to minimizeconfusion as much as possible, but inevitably there will be adjacent Colors thatare hard to tell apart. To improve contrast, a few Colors have been duplicatedfor units widely separated in space and time. For example, Colors for earlyPaleozoic volcanic units (found only in the Appalachians) have also been usedfor some units in the far West.

Some periods are divided in some locations and undivided in others. Undividedperiods generally use the middle Color for the period. In practice this seems toresult in little confusion. If adjacent units are other divisions of the period,the Color represents a subdivision. If adjacent units are different periods, theunit is undivided.

Symbols

Periods

Units of undivided age

Combinations of symbols refer to transitional or undivided units. For exampleDS refers to undivided Devonian and Silurian rocks.

Prefixes

Suffixes

References

Principal sources for data. Links, even those of government agencies, go out of date quickly and are mostly not provided. Search by title and publication number to find links to data.

Conterminous US Geology
US Geological Survey: Mineral Resources; Geology of the conterminous United States. A digital version of the Geologic Map of the United States, originally published at a scale of 1:2,500,000 (King and Beikman, 1974b). Excludes Alaska and Hawaii.
Detailed Geology of States
US Geological Survey: Mineral Resources: Online Spatial Data; Geologic maps of US states
US Bouguer and Isostatic Gravity
US Geological Survey: Mineral Resources; Online Spatial Data; Gravity anomaly grids for the conterminous US. Contoured with Global Mapper 14
US Magnetic Anomalies
  • US Geological Survey: Digital data grids for the magnetic anomaly map of North America: Open-File Report 02-414. Contoured with Global Mapper 14
  • 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. Contoured with Global Mapper 14
  • Digitized Aeromagnetic Datasets for the Conterminous United States, Hawaii, and Puerto Rico, U.S. Geological Survey Open-File Report 99-0557
Canada Geology
Wheeler, J.O., Hoffman, P.F., Card, K.D., Davidson, A., Sanford, B.V., Okulitch, A.V., and Roest, W.R. (comp.) 1997: Geological Map of Canada, Geological Survey of Canada, Map D1860A.
Canada Bouguer Gravity and Magnetic
Natural Resources Canada; Earth Sciences Sector; Geoscience Data Repository. Contoured with Global Mapper 14
Magnetic Anomalies outside US
US Geological Survey: Digital data grids for the magnetic anomaly map of North America: Open-File Report 02-414
Offshore Geology
Mostly from US Geological Survey; Resources for the Geologic Map of North America; GIS Files (shapefiles); (ESRI geodatabase only is USGS DR-424)
Western Mexico Geology
US Geological Survey; Resources for the Geologic Map of North America; GIS Files (shapefiles); (ESRI geodatabase only is USGS DR-424)
Eastern Mexico and Gulf of Mexico Geology
US Geological Survey OFR 97-470-L; Map Showing Geology, Oil and Gas Fields, and Geologic Provinces of the Gulf of Mexico Region; Digitally Compiled by Christopher D. French and Christopher J. Schenk
Caribbean Geology
  • US Geological Survey OFR 97-470-K; Map Showing Geology, Oil and Gas Fields, and Geologic Provinces of the Caribbean Region; Digitally Compiled by Christopher D. French and Christopher J. Schenk
  • Hearn, P., Jr., Hare, T., Schruben, P., Sherrill, D., LaMar, C., and Tsushima, P., 2001, Global GIS Database, Digital Atlas of Central and South America: U.S. Geological Survey Digital Data Series DDS-62-A. [on-line] available at: http://webgis.wr.usgs.gov/globalgis/
  • U.S. Geological Survey World Energy Assessment Team, 2000, U.S. Geological Survey World Petroleum Assessment 2000: U.S. Geological Survey Digital Data Series DDS-60, 4 CD-ROMs. [on-line] available at: http://pubs.usgs.gov/dds/dds-060
Arctic Offshore and Greenland
Maps showing Geology, Oil and Gas Fields, and Geologic Provinces of the Arctic; Compiled by Feliks M. Persits and Gregory F. Ulmishek; U.S. Geological Survey Open File Report 97-470-J
Ocean Floor Isochrons
Muller, R. D., M. Sdrolias, C. Gaina, and W. R. Roest (2008), Age, spreading rates, and spreading asymmetry of the world's ocean crust, Geochem. Geophys. Geosyst., 9, Q04006, doi:10.1029/2007GC001743. On-line through NOAA;  Age, spreading rates and spreading symmetry of the world's ocean crust (Version 3, September 2008) Contoured using Global Mapper 14.

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Created 23 July 2001, Last Update 15 January 2020