Geologic Map of Alabama and Mississippi

Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay
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Geology with One-Degree Grid

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Geology with Highways

US highways are red, interstates are gold. Refer to a road map for route numbers - this map is busy enough without them! I recommend using the plain map for geologic interpretation, with this map used for more specific location information.

Topography

Legend

Marine refers to well-stratified rocks mostly (but not entirely) of marine origin. Eugeo refers to eugeosynclinal rocks, that is, deep-water sedimentary rocks of continental slope or trench origin. Other headings are self-explanatory.

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

Some periods are divided in some locations and undivided in others. Undivided periods generally use the middle color for the period. In practice this seems to result in little confusion. If adjacent units are other divisions of the period, the color represents a subdivision. If adjacent units are different periods, the unit is undivided.

Symbols (U.S.)

Periods Units of undivided age
Q    Quaternary    2 Ma - 0ms    schist and phyllite
Qh    Holocene    10 Ka - 0m4    granite gneiss
Qp    Pleistocene    2 Ma - 10 Kam3    migmatite
T    Tertiary    65 - 2 Mam2    amphibolite
Tp    Pliocene (Neogene) 5-2 Mam1    felsic gneiss and schist
Tm    Miocene (Neogene) 23-5 Macat    cataclastic rocks
To    Oligocene (Paleogene) 33-23 Maum    ultramafic rocks
Te    Eocene (Paleogene) 55-37 MaPrefixes
Tx    Paleocene (Paleogene) 65-55 Mau    upper
K    Cretaceous    145 - 65 Mal    lower
J    Jurassic    208 - 145 Ma Suffixes
Tr    Triassic    245 - 208 Ma Numbers and numbers with letters (2, 3a, etc) represent subdivisions of periods. See the Geologic Map of the United States for specific stratigraphy.
Pm    Permian    286 - 245 Ma a    anorthosite (precambrian); andesite (Tertiary)
P    Pennsylvanian    320 - 286 Ma b    pillow basalt
M    Mississippian    360 - 320 Ma c    continental deposits
D    Devonian    408 - 360 Ma e    eugeosynclinal deposits
S    Silurian    428 - 408 Ma f    felsic volcanic rocks
O    Ordovician    505 - 428 Ma g    granitic rocks. May have number suffixes to distinguish different ages.
C    Cambrian    570 - 505 Magn    gneissic rocks
Z    Precambrian Z    900 - 570 Mai    undivided intrusive rocks
Y    Precambrian X    1600 - 900 Ma m   undivided metamorphic rocks
X    Precambrian Y    2500 - 1600 Ma mi    mafic intrusive rocks
W    Precambrian W    4600 - 2500 Ma q    quartzite (Cambrian and Precambrian Y only) Precambrian Y quartzite is not shown on the Geologic Map of the United States and is used for the Sioux, Barron, Baraboo and related quartzites of the upper Midwest.
  s    syenite
 v    mafic and intermediate volcanic rocks
Combinations of symbols refer to transitional or undivided units. For example DS refers to undivided Devonian and Silurian rocks.

'    Phanerozoic metamorphic overprint, usually amphibolite grade or above; Paleozoic in Appalachians, Mesozoic and Tertiary in the West.

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. Be sure to spell Beikman correctly when searching.
Detailed Geology of States
US Geological Survey: Mineral Resources: Online Spatial Data; Geologic maps of US states
US Bouguer Gravity
US Geological Survey: Mineral Resources; Online Spatial Data; Gravity anomaly grids for the conterminous US
US Isostatic Gravity
US Geological Survey: Mineral Resources; Online Spatial Data; Gravity anomaly grids for the conterminous US
US Magnetic Anomalies
  • US Geological Survey: Digital data grids for the magnetic anomaly map of North America: Open-File Report 02-414
  • 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
  • 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
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 24 April 2013

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