Geologic Map of Louisiana
Steven Dutch, Professor Emeritus, Natural and Applied Sciences, University of Wisconsin - Green Bay
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Gravity and Magnetic Maps of the States
Scale: 1 pixel = 1 km. 10-degree grid; Lambert Conformal Conic Projection, Center 32N 88W
Legend
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.
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 - 0 | ms schist and phyllite |
| Qh Holocene 10 Ka - 0 | m4 granite gneiss |
| Qp Pleistocene 2 Ma - 10 Ka | m3 migmatite |
| T Tertiary 65 - 2 Ma | m2 amphibolite |
| Tp Pliocene (Neogene) 5-2 Ma | m1 felsic gneiss and schist |
| Tm Miocene (Neogene) 23-5 Ma | cat cataclastic rocks |
| To Oligocene (Paleogene) 33-23 Ma | um ultramafic rocks |
| Te Eocene (Paleogene) 55-37 Ma | Prefixes |
| Tx Paleocene (Paleogene) 65-55 Ma | u upper |
| K Cretaceous 145 - 65 Ma | l 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 Ma | gn gneissic rocks |
| Z Precambrian Z 900 - 570 Ma | i 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 exampleDS 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 11 January 2020