Stratigraphic units, correlated on this chart along three generally west east lines crossing mountains and basins (Figure 1) and shown on the Geologic map of Wyoming (scale 1:500,000; Love and Christiansen, 1985), were compiled for the Wyoming Geological Association (Love and Christiansen, 1980) from individual geologic maps of the 1°x 2°, 1:250,000 scale quadrangles of the State (Figure 2). The chart has been revised to agree with the ages and units shown on the 1985 State geologic map and explanation except where necessary to reflect subsequent revisions. Ver Ploeg added the subsurface terminology. Ages, in millions of years (Ma), of system and series boundaries are shown beside the series columns (see footnote 14 for references; also see Obradovich and Sutter, 1984, for age of Tertiary Cretaceous boundary). Figure 3 shows North American Land Mammal Ages and radioisotopic chronology for the Paleogene and Neogene.

Although general age relations are indicated on the chart, subtleties of unit age changes from west to east or from north to south across the State are not shown. Neither relative thicknesses of stratigraphic units nor relative duration of time is implied by the arbitrary vertical dimension of the chart, selected mainly to accommodate space required for lettering.

Most Quaternary aurficial end glacial deposits, as well as some Tertiary units such as the Tunp, Angelo, and Fossil Butte Members of the Wasatch Formation, are not shown on the chart although they may be shown on the 1° x 2° geologic quadrangle maps. An arbitrary cutoff between basins and uplifts in adjacent columns was made; it is not the same across the chart.

Basic references used for the chart are shown for each column in "Primary Sources of Data for Columns"; references cited on the chart or in the footnotes are given in "Selected References", as are other general references consulted but not cited. All sources of data used in the compilation of the 1° x 2° maps and the 1985 State geologic map are listed on sheet 3 of the State geologic map. The 1° x 2° geologic maps generally include an index to the mapping used for their compilation; most of those maps include lithologic descriptions and thicknesses for the stratigraphic units. Other references consulted but not listed are various guidebooks of the Wyoming Geological Association.

The authors thank their colleagues in the U.S. Geological Survey, the Geological Survey of Wyoming, and the Wyoming Geological Association for the time they generously spent consulting with the authors on problems of age and correlation.


Wyoming Stratigraphic Chart Legend
Wyoming Stratigraphic Chart Legend

Basin Uplifts
Figure 1: Map of Wyoming showing areas listed in columns A-U 1, Yellowstone volcanic area to Black Hills; 2, Teton Range to Denver Basin, Thrust Belt to Laramie Basin.

Figure 2
Figure 2: Index map of Wyoming showing locations of 1° x 2° quadrangles and corresponding geologic maps published or open filed by the U.S. Geological Survey (blue) and the Geological Survey of Wyoming (yellow).

Figure 3
Figure 3: Classification and generalized ages of Paleogene and Neogene sequences
in Wyoming. North American Land Mammal Ages (NALMA) and radioisotopic chronology, in MA, are shown in the right-hand column. Paleogene from Lillegraven
(in preparation); Neogene is modified from Woodburne (1987), and Swisher and
Prothero (1990).

Camera Icon (Photos to Wyoming Stratigraphic Chart) Camera Icon Example
Camera Icon indicates there is a photo for the specific formation within the stratigraphic chart. Click camera icon to see example.

Footnotes Example Footnote Example   - As seen in this example footnotes (Number underlined in orange) are clickable which directs you to the footnote within the Source Information webpage within the Wyoming Stratigraphy Website. Click footnote number to see example.