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Wyoming Statigraphy
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.
Explanation
Wyoming
Stratigraphic Chart Legend
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: 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: 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 indicates there is a photo for the specific formation within the
stratigraphic chart. Click camera icon to see 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.
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