This study focuses on the geomorphology and geochronology of dunes formed on three sandy barrier systems at Clark, Europe and Kangaroo Lakes in Wisconsin's Door Peninsula. The Lake Michigan shoreline in the peninsula contains abundant evidence for fluctuations in lake level with paleo-shoreline features that lie up to ~7 m above the present shoreline. Dunes are not very common along the Lake Michigan shoreline in Wisconsin, but the three bay barriers studied contain beach ridges that were buried by varying depths of eolian sand in the form of low relief sandsheets as well as parabolic and transverse dunes that have relief of up to 21 m. The purpose of this study was to document when the barriers formed and when the subsequent eolian activity occurred. The chronology presented here for barrier emplacement and dune development is based on 65 optically stimulated luminescence (OSL) samples which were collected from littoral sediment in the barriers (n = 17) and the overlying eolian sand (n = 48). Sediment samples were collected using bucket augers or a vibracoring device at depths ranging from 0.5 to 4.1 m below the ground surface. The OSL ages show that barriers in each of the study sites were constructed between ~5.9 and 3.9 ka, corresponding closely to the Nipissing high lake phase. OSL ages falling between 3.3 and 2.5 ka at the Kangaroo Lake site suggest the portion of the barrier closest to Lake Michigan formed during the Algoma phase. The majority of the eolian ages fall into two primary groups that overlap with or are slightly younger than the ages acquired from the barriers. These results suggest eolian activity ended between 4.5 and 3.7 (n = 20 ages) and 2.5 and 1.8 (n = 11 ages) ka. Both geomorphic and geochronological evidence suggests that dune development occurred rapidly when sand supply increased as lake levels fell following these two transgressive events.

A Twocreekan organic horizon, which is underlain by till of the Haven Member and overlain by till of the Two Rivers Member of the Kewaunee Formation, was investigated near Kewaunee, Wisconsin. Wood from this horizon was dated at 11,700 ± 110 B.P. (ISGS-1061) and 11,650 ± 170 B.P. (ISGS-1234). The insect fauna from the Kewaunee site has many elements in common with the insects from the type section of the Two Creeks Forest Bed, 14 km to the south. These include the northwestern carabid Asaphidion yukonense , northern carabids Carabus taedatus and Bembidion grapii , and the northern staphylinid Acidota quad rata . In contrast, the Kewaunee site fauna appears to have inhabited a somewhat colder environment, as suggested by the occurrence of the carabids Cymindis unicolor and Pterostichus (Cryobius) spp. We interpret the Kewaunee specimens of aquatic, water-marginal, and upland species to represent an allochthonous rather than an autochthonous assemblage.

A complex of abandoned Lake Michigan beach ridges at Baileys Harbor, Wisconsin was investigated to establish the type, onset, and periodicity of ridge-forming processes. A further objective of the study was to place the development of the complex into the context of the postglacial history of the Great Lakes region. Surface profiles were constructed, and samples of sediment and peat were collected and analyzed. Results of pollen and radiocarbon analyses were used to infer the kind and timing of climatic conditions affecting lake levels, ridge accretion, and peat accumulation. A suggestion is made for an asymmetrical rate of change between high and low lake levels. The ridges accreted during four episodes of low or falling lake levels separated by three periods of high or rising water, during which erosion of earlier ridges occurred. Peat first began to accumulate in the interridge swales after the first erosional event, and construction of a truncating ridge began not long before 1,000 B.P. A pollen core extracted from behind the oldest ridge revealed a vegetational sequence that closely corresponds with post-Algoma lake-level fluctuations reported by other workers for the Lake Michigan basin.