The Ferris Dune Field of south-central Wyoming lies in a topographically-regulated “corridor” of high wind that extends over much of southern Wyoming. Examination of geomorphology, sedimentology, and stratigraphy reveals that winds did not vary significantly in either average direction or speed during the Holocene period, but variations in precipitation, and hence plant growth, produced varying degrees of eolian activity. Deposition of dune sand resulted mainly from a decrease in the carrying capacity of the wind as it encountered the Ferris-Seminoe Mountain barrier. The Ferris dunes geomorphically resemble other dune fields in the western United States. Phytogenic dunes, varying in size and shape from small blowout dunes to large, well-developed parabolic dunes, dominate the landscape. A few actively migrating dunes occur both where the stabilized ground surface has been disturbed and where the highest wind speeds occur. Mineral analyses indicate that the Ferris dune sands were derived primarily from the Tertiary Battle Spring Formation. The Killpecker Dune Field “tail” sands and certain Cretaceous through Paleocene sandstones exposed along the Lost Soldier Divide were lesser contributors. The valley of Clear Creek reveals a relatively continuous Holocene section of interbedded dune and interdunal pond deposits. Bioturbated, low-angle (less than 15°) bedding, which characterized large portions of the eolian sands exposed there, attests to the long-term influence of vegetation and moisture on dune activity. Artifacts recovered in the vicinity of Clear Creek demonstrate Late Plains Archaic to Late Prehistoric occupations in this area. Radiocarbon dates from Clear Creek, comparison of Clear Creek chronology to other radiometrically-dated geologic-climatic events from the western United States, and theoretical dune migration rates reveal a general sequence of geologic-climatic events for the Ferris Dune Field: Eolian activity had begun in the Ferris-Lost Soldier area by at least ca. 9,950 to 10,330 years b.p. Major depositional intervals (indicating widespread Ferris dune activity) correlate with two radiocarbon-dated periods of drought. The first occurred between ca. 7,660 and 6,460 years b.p.; the second occurred following ca. 6,460 years b.p. (and lasted until ca. 5,500 years b.p.). Since the last major depositional (drought) interval, the climate in the Ferris-Lost Soldier area has moderated. Drought intervals have been short and vegetation has largely stabilized the dunes.

Eolian landforms are the natural result of the action of strong winds on an exposed land surface. Certain characteristics of the wind can be interpreted from these landforms. The spacing of sand dunes and draas (dune groups) is one parameter that can be used to estimate wind velocity and available wind power. LANDSAT imagery or aerial photography may be used to identify the eolian landforms, and measurements of spacings can be made directly from these datum. Fourier analysis of these measurements reveals the predominant spacings. Assuming that shear velocity is the dominant factor determining the wave length of bedforms, the spacing (λ) can be used to compute the threshold shear velocity (V *T ) using mathematical relationships derived by Wilson (1972): V ′ * T = 2.06 λ 1 / 3 cm / sec ( dunes ) V ′ * T = 0.59 λ 1 / 3 cm / sec ( draas ) These values may then be used to estimate wind velocity at any other height above the surface or to estimate available wind power. The Killpecker and Seminoe Dune Fields in south-central Wyoming were used as test areas in which to demonstrate this technique.