Well-developed simple, stabilized parabolic dunes that are oriented to the east and southeast form the inland portion of a dune complex that extends ~32 km east-west across the southern shoreline of Lake Michigan in northwest Indiana. To better understand shoreline evolution during the Nipissing and post-Nipissing phases of Lake Michigan, subsurface sedimentology and radiocarbon ages from interdunal wetlands are considered with optical ages from nearby dunes within the landward portion of this area known as the Tolleston Beach. In the east, the once expansive Great Marsh had developed during the lake-level fall from the Nipissing peak (~4500 years ago). Units of eolian sand found within vibracores from the Great Marsh indicate that dunes formed and began migrating into the wetlands 4200–4400 years ago. In the west, newly formed dunes migrated along the shoreline while small interdunal wetlands formed shortly thereafter. Optical ages from two individual dunes indicate that this relict dune system stabilized by ~3500 years ago. Six samples collected from each of the two dunes yield optical ages that overlap at two standard errors. However, variations in individual ages detect episodic processes of sand movement that distinguish between the timing of landform migration and stabilization. Optical ages collected at the base of the slipface are interpreted as the age of landform stabilization. This study indicates that, with focused field-to-lab strategies, optical dating can provide a more robust chronology of shoreline development than previously considered; correlating eolian activity to wetland development and lake-level change in the Great Lakes.

The youngest dune belt along Lake Michigan's southern coast evolved through four stages. The first stage began during the Nipissing transgression, ~6.0 ka, and culminated at the Nipissing high, ~4.5 ka. Rising lake levels eroded the lake margins and generated sediment that was transported to southern Lake Michigan, creating the Tolleston barrier beach. The second stage, beginning ~4.5 ka with a rapid lake level fall and continuing to ~3.0 ka, represents a major episode of transgressive parabolic dune field development. Large, simple parabolic dunes, with easterly apices (85–105° azimuth) suggestive of westerly wind formation, developed in a sand belt ~1–2 km wide. The third stage, from ~3.0 to 1.0 ka, was characterized by strandplain progradation and transverse ridge development west of Miller, Indiana, and dune stabilization creating the Holland Paleosol east of Miller. Sporadic blowout activity from strong westerly winds redistributed the sand within the dune field, amalgamating simple dune forms into compound, rake-like, and nested parabolic dunes. The fourth and youngest stage, beginning ~1.0 ka, represents blowout development in a southeasterly direction (120–135° azimuth), indicating a wind direction shift to the northwest. Blowouts, whether developed in transverse ridges or in the northern arms of parabolic dunes, occur closest to the lake. The timing of this blowout initiation coincides with a rise in the level of Lake Michigan. However, a more likely development and maintenance mechanism for these dunes is increased storminess with strong northerly and northwesterly winds during the cooler months of the year.

Ground penetrating radar (GPR) was used to investigate the internal structure and development of an active parabolic sand dune in the Bigstick Sand Hills of southwestern Saskatchewan, Canada. The radar survey was conducted in a grid configuration using 250 MHz antennas. The radar frequency and the properties of the aeolian sands limited the penetration of the radar signal to the uppermost 4 m. Radar profiles parallel to the prevailing westerly wind reveal three zones with differing structural arrangements that are interpreted to represent three phases in the development of the dune: (1) underlying low-angle reflections representing preexisting aeolian strata associated with sand sheet or dune marginal deposition; (2) high-angle reflections representing downwind migration by grainflow; and (3) a variety of high- and moderate-to-low-angle reflections representing a more complex pattern of migration involving grainflow, grainfall, and ripple deposition. Radar profiles perpendicular to the prevailing wind are characterized by convex-up and concaveup reflections along the dune head and are interpreted as spur and trough structures, respectively. Radar profiles over the wings reveal an arrangement of high-angle reflections radiating away from the center of the dune. The main structural features from the radar profiles are summarized into two radar surfaces; three radar packages; and three radar facies, one of which has two subfacies. Observations of exposed surface stratigraphy following extensive wind erosion lend support to the interpretations made from the GPR data.

Abstract The Provincelands in the Cape Cod National Seashore developed about 5 ka from wind- and waterborne Outer Cape Cod outwash sands as sea level rose to submerge offshore banks. A late Holocene chronology of sand dunes in the Provincelands is established from radiocarbon-age determinations on the basal organics from interdunal bogs and ponds. The Provincelands ponds, thought to be lakes trapped behind hooked spits, are shown here to have developed from bogs similar to those in the extant parabolic-dune field. An older, stabilized dune field in the location of the ponds is hypothesized. Episodes of alternating dune movement and interdunal-wetland formation in the Provincelands correlate with climatic changes in the North Atlantic and elsewhere during the last 1.2 ka, as interpreted from ice core, glacier movement, sea-surface temperature, tree-ring, pollen, and historical data. The dune field data suggest a periodicity of change of 0.2 ka. Before about 1.2 ka, dunes in the Provincelands were active. Between about 1.15 and 0.9 ka, bogs formed which, at least in the west-central area of the Provincelands, developed into ponds having continuous organic sedimentation until today. This evidence indicates that the west-central dune field stabilized after 1.1 ka. Between 0.9 and 0.7 ka, dunes were active in the north and east-central Provincelands, but from about 0.7 to 0.5 ka, bogs formed within that dune field, and at least one bog in the west-central area became a pond, both events indicating a warm and wet climate. During the Little Ice Age (0.5 to ∼0.2-0.1 ka), the Provincelands dunes were active, suggesting a cold, windy, and dry climate. Because of a warmer and wetter climate during the last 0.1 ka, bogs have formed again within the dunes.

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.