ABSTRACT The last-glacial megaflood Kankakee Torrent streamlined hills and the remarkably straight backslope of the Kalamazoo moraine (Lake Michigan lobe of the Laurentide ice sheet) in southwestern Michigan. Flooding ensued as proglacial Lake Dowagiac overflowed across remnants of the Lake Michigan lobe at the position of the inner margin of the Kalamazoo moraine as glacial debris and ablating ice were pinned against Portage Prairie. Proglacial Lake Dowagiac developed in the Dowagiac River valley as the lobe retreated to form the Valparaiso moraine. A minimum age of the Kankakee Torrent (18.7 ± 0.6 k.y. B.P) is indicated by the weighted mean value of six optically stimulated luminescence ages determined from quartz sand in glaciofluvial sediment on the Kalamazoo moraine (Lake Michigan and Saginaw lobes). This value is consistent with tighter age control based on radiocarbon ages of tundra plants within silty sediment forming ice-walled lake plains and in a torrent-scoured lake basin (Oswego channel) in Illinois. Crosscutting relationships of well-dated moraines indicate the Kankakee Torrent occurred sometime between 19.7 and 18.9 calibrated (cal.) k.y. B.P. as it skirted the south margin of the Valparaiso Morainic System.

ABSTRACT The Eagle Lake basin was formed by collapse of the ablating Lake Michigan lobe over a tunnel valley and subsequent reoccupation of the collapse basin by the lobe during local final phase of glaciation. Latest collapse occurred prior to about 16,250 but after 18,600 cal yr B.P. A hydrologically open lake occupied Eagle Lake basin from 16,250 cal yr B.P. to the present. The lake was described in 1834 by the original land survey, but was drained for agriculture by 1939.

ABSTRACT This field guide discusses the dune types and processes, ecology, and geomorphic history of the largest freshwater dune systems on the southeastern shore of Lake Michigan. From north to south, stops include P.J. Hoffmaster State Park, Gilligan Lake/Green Mountain Beach Dune, Saugatuck Harbor Natural Area, and Grand Mere and Warren Dunes State Parks, Michigan. All of the sites are low, perched transgressive dune complexes. Moving from the lake inland, the typical dune complex in this area consists of incipient foredunes, an established foredune ridge, a parabolic dune complex, and a back-dune ridge complex. All stages of ecological succession are typically present in the larger dune complexes. Surface changes in Lake Michigan dunes are driven by spatial gradients in sand flux, which, in turn, are determined by a complex interaction among wind dynamics, vegetation patterns, and preexisting topography. Surface change patterns are modified by seasonal effects, with the majority of sand transport being associated with strong storms in the autumn, winter, and early spring. Sand can be temporarily stored in niveolian deposits during the winter, leading to oversteepened slopes, which collapse during the spring thaw. Current dune complexes largely formed during and after the rise in lake levels to the Nipissing high lake level, ca. 4.5 ka. Broad fields of relatively low dunes developed during the lake-level drop following the Nipissing high. Beginning with the rise to the Algoma high lake level, ca. 3.2 ka, the lakeward edges of these fields were episodically reworked, forming large parabolic dune complexes. A period of widespread dune stability formed the Holland Paleosol, a spodic inceptisol. Dune growth and migration resumed prior to European settlement of the area and continues today. Foredune complexes grow wider and higher during periods of low lake levels, but narrow during periods of high lake level due to scarping at their lakeward edges.

ABSTRACT The Indiana Dunes is a name commonly used for the eastern part of the Calumet Lacustrine Plain, generally referring to the large dunes along the coast from Gary, Indiana, eastward to the Michigan state line. However, the Calumet Lacustrine Plain also contains complex coastal landscapes associated with late Wisconsin to Holocene phases of ancestral Lake Michigan (e.g., mainland-attached beaches, barrier beaches, spits), including those formed during quasi-periodic decadal and shorter-term waterlevel variability that characterize modern Lake Michigan (e.g., beach ridges, dunes, interdunal wetlands). Major industrial development and other human activities have impacted the Calumet Lacustrine Plain, often altering these landscapes beyond recognition. Today, geological and paleoenvironmental data are sought to inform regional environmental restoration and management efforts and to increase the resiliency of the coastal landscape to ongoing disturbances. During this field trip, we will examine the relict shorelines and their associated nearshore and onshore features and deposits across the Indiana portion of the Calumet Lacustrine Plain. These features and deposits record the dynamic interaction between coastal processes of Lake Michigan, lake-level change, and long-term longshore sediment transport during the past 15,000 yr. Participants will examine the modern beach, the extensive beach-ridge record of the Tolleston Beach strandplain, a relict dune field, and the large dunes of the modern shoreline, including Mount Baldy. At Mount Baldy, we will focus on the landscape response to human modification of the shoreline. We will also explore the science behind dune decomposition chimneys—collapse features that caused a 6-yr-old boy to become buried more than 3.5 m below the dune surface in 2013 and highlighted a previously unrecognized geologic hazard.

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.

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.

Interrelationships among late Holocene climate, the dynamics of coastal dunes and sedimentation in adjacent small lakes along coasts of the upper Great Lakes have been studied for over a decade. Nonetheless, many questions remain as to relationships between climate variability and dune activity. The study site is Oxbow Lake, near Saugatuck, Michigan, which formed as an artificial cutoff of the Kalamazoo River in 1906. Stratigraphic control of the infilled western end of the lake is from ground penetrating radar, and lake sediment from Livingstone and Glew cores with age control from 210 Pb/ 137 Cs/ 7 Be analysis. The climate data used included Lake Michigan water levels and temperature, precipitation, drought and evaporation data from a weather station 30 km to the south and wind data from buoys on Lake Michigan. Episodic peaks of eolian sand in the lake sediment are interpreted to be sourced from adjacent small parabolic dunes along the shoreline and from a foredune west of the lake. Linear regressions of the climate data and weight percent sand resulted in a variety of correlations, some conflicting, and with uncertain meanings. It was found through visual correlation that peaks in sand correspond with both peaks in water levels of Lake Michigan and the winter Palmer drought severity index. The implications of this research are that dune activity is linked to periods of wet conditions and storminess, contrary to typical eolian environments, but consistent with other studies in temperate coastal dunes along the Great Lakes. Results can be used as a modern analogue for coastal dune activity during times of high lake level.

This study investigates the impacts of extratropical cyclones on Lake Michigan dune complexes by integrating field measurements and meteorological data from sites along the southeastern shore. Surface changes and wind velocities were monitored at Hoffmaster State Park, Saugatuck Harbor Natural Area, and Mount Baldy at Indiana Dunes National Lakeshore from October to April in 2010–2011 and 2011–2012. Over 70% of the events with wind speeds at least two standard deviations above the mean were associated with extratropical cyclones. The wind directions depended on the cyclone path, with westerly or southerly components most common. Local conditions moderated the effects of storm winds on surface change. The greatest surface changes measured in a trough blowout at Saugatuck Harbor Natural Area were associated with regional winds with a component blowing up the lee slope that produced bifurcated windflow within the trough. While the orientation of a given dune strongly influences the amount of surface change, it does not always follow a simple pattern deduced from dune geometry. Surface changes at Hoffmaster State Park and Saugatuck Harbor Natural Area during a normal winter (2010–2011) and an unusually warm winter (2011–2012) suggest that colder weather conditions inhibited net transfer of sand from the beach but had less impact away from the shore. Moisture also inhibited sand transport, but strong storm winds moved wet sand, sometimes over long distances at Indiana Dunes National Lakeshore. Overall our results show that winds associated with extratropical cyclones play a vital role in the development of Lake Michigan dune complexes.

The evolution of Great Lakes coastal dunes includes long-term trends and short-term variations. This study explores multi-year, interannual and seasonal patterns of change as a Lake Michigan foredune responds to variations in lake level, weather and surface conditions. The study site is an active foredune in P.J. Hoffmaster State Park on the east coast of Lake Michigan. Foredune changes, local conditions and processes were monitored from 2000 to 2012 with repeated ground surveys, erosion pins, microclimate measurements, and observations of surface conditions. Additional weather and lake-level data were obtained from regional sources. Study results show a trend of foredune growth during the multiyear study period, with interannual and seasonal variations in the rates and spatial patterns of dune growth. At the scales of investigation, relationships between dune change and variables could not be quantified, but patterns of foredune change and influential variables were identified. The greatest amounts of erosion and deposition took place during the autumn and winter when strong winds were the most frequent, but storm conditions, vegetation changes, precipitation, snow, and ground freezing affect the availability of sand for transport by wind. Study results suggest that event-scale research is needed for understanding interactions between variables and the foredune, but mesoscale studies such as this one are crucial for identifying cumulative patterns of dune change and the role that events play in the larger scale patterns of dune evolution.

Remote sensing and geospatial analysis techniques allow for better understanding of dynamic landforms such as sand dunes. Our study investigated to what extent geospatial analysis of historic aerial photographs could be used to detect changes in dune activity over time at three Lake Michigan parabolic dunes in western Michigan, USA. We georeferenced historic aerial photographs, dating from 1938 to 2008, and then used edge-detection in remote sensing software ERDAS Imagine to distinguish bare sand from vegetated areas. The photos were then imported into the geographic information system ArcGIS, where they were reclassified and vectorized to create bare-sand outlines. Further analysis in ArcGIS allowed us to determine the changes over time to the bare-sand areas and the movement of the edges between bare sand and vegetation along the central axis of the dunes. Results show significant variability in each dune's bare-sand area during the study period, although only small increases in bare-sand area were recorded from the beginning to the end of the study. An indicator of continuing dune activity is the eastward advance of the inland edge of each bare-sand area from 1938 to 2008. Understanding changes in dune activity, especially long-term variation, through utilizing these geospatial technologies offers new insights and opportunities for research in the ongoing study and management of west Michigan dunes.

ABSTRACT This field guide explores the geomorphology, ecology, contemporary processes, sedimentary structures, and geomorphic history of the large freshwater dune systems on the southeastern shore of Lake Michigan. Recent research studies on varying aspects of the dunes are highlighted at each stop. From north to south, these stops include P.J. Hoffmaster State Park near Muskegon, Michigan; Gilligan Lake and Green Mountain Beach southwest of Holland, Michigan; Saugatuck Dunes State Park and Saugatuck Harbor Natural Area, both near Saugatuck, Michigan; Warren Dunes State Park and Grand Mere State Park between the Indiana–Michigan border and Benton Harbor, Michigan; and Mount Baldy on the eastern edge of the Indiana Dunes National Lakeshore, Indiana. All of the complexes described are low perched transgressive dune complexes that are migrating inland over former lake plains or baymouth bars. Moving from the lake inland, the typical dune complex in this area consists of incipient foredunes, an established foredune ridge, a parabolic dune complex, and a back-dune ridge complex. All stages of ecological succession—beginning with a pioneer community dominated by beach grasses and ending with a mesic forest dominated by oak, maple, and beech—are typically present in the larger dune complexes. Like coastal dunes everywhere, surface changes in Lake Michigan dunes are driven by spatial gradients in sand flux, which, in turn, are determined by a complex interaction among wind, vegetation patterns, and preexisting topography. The patterns of surface change are modified by seasonal effects, with the majority of sand transport being associated with strong storms in the autumn, winter, and early spring. Sand can be temporarily stored in niveolian deposits during the winter, leading to oversteepened slopes, which collapse during the spring thaw. A variety of sedimentary bed forms and structures can be viewed in dunes along the southeastern shore of Lake Michigan, including wind ripples, lag deposits, raindrop impressions, adhesion ripples, adhesion warts, eolian turrets, sand pedestals, surface patches of fine-grained dark sand, pinstripes, paleosols, cross-bedding, climbing ripple lamination, niveolian deposits, and avalanche lobes. Most of these features are best seen immediately after strong storms in the autumn and winter. Remnants of older dune surfaces are exposed in a few places in back-dune ridge complexes; however, the current dune complexes are largely a product of events that occurred during and after the rise in lake levels to the Nipissing peak (ca. 4.5 ka). Broad fields of relatively low dunes developed during the drop in lake levels following the Nipissing peak. Beginning with the rise to the Algoma high lake level (ca. 3.2 ka), the lakeward edges of these fields were episodically reworked, forming the large parabolic dune complexes. A period of widespread dune stability resulted in the development of the Holland Paleosol, a particularly well-developed paleosol with Spodosol characteristics. Widespread dune growth and migration resumed prior to European settlement of the area and continue today.