Dune Formation Research Articles

Age-depth modelling and the effect of including – or not – shared errors across sets of OSL samples: The case study of Beg-er-Vil (Brittany, France)

The coastal site of Beg-er-Vil (Brittany, France) has yielded remains of a dwelling site from the Mesolithic period, dating back to ca. 8000 years ago. These archaeological remains were covered by a marine sand dune. Among the research questions raised by recent excavations, the timing of the dune formation with respect to the human occupations is of particular interest: how much time elapsed between these two events? To resolve this question, we employed radiocarbon dating to infer the timing of human occupations and OSL dating to date the dune aggradation. We combined radiocarbon and OSL data in a Bayesian framework, including stratigraphic constraints and measurement errors shared across OSL samples, to build a robust and precise chronological model of the site. We then built an age-depth model for the dune to determine the onset of dune formation. We conclude that we cannot detect a time gap between the latest human occupations and dune aggradation. Finally, we demonstrate how stratigraphic constraints and shared errors affect – and improve – the precision of the chronology inferred from our measurements.

The distribution and impact of an invasive plant species (Senecio inaequidens) on a dune building engineer (Calamagrostis arenaria)

Disturbance is thought to enhance the probability of invasive species establishment, a prerequisite for naturalisation. Coastal dunes are characterised by disturbance in the form of sand dynamics. We studied the effect of this disturbance on the establishment and spread of an invasive plant species (Senecio inaequidens) in European coastal dunes. Local sand dynamics dictate the spatial configuration of marram grass (Calamagrostis arenaria). Therefore, marram grass configuration was used as a reliable proxy for disturbance. Since marram grass plays a crucial role in natural dune formation, we evaluated the possible effects S. inaequidens could have on this process, if it is able to naturalise in European coastal dunes. We expected the highest probability of S. inaequidens establishment at intermediate marram grass cover because too low cover would increase sand burial, whereas high cover would increase competition. However, our results indicate that S. inaequidens is quite capable of handling higher levels of sand burial. Thus, the probability of S. inaequidens establishment was high under low marram cover but slightly lowered when marram cover was high, hinting at the importance of competition. We expected a negative impact of Senecio-altered soils on marram grass growth mediated by soil biota. However, marram grass grew better in sand gathered underneath Senecio plants due to abiotic soil modifications. This enhanced growth may be caused by Senecio leaf litter elevating nutrient concentrations in an otherwise nutrient-poor substrate. If such increased plant growth is a general phenomenon, further expansion of S. inaequidens could accelerate natural succession in European coastal dunes.

Calculation of the Rub’ al Khali Sand Dune Volume for Estimating Potential Sand Sources

The Rub’ al Khali desert (or Empty Quarter) is the largest and perhaps most significant sand sea in the world. Located on the southern Arabian Peninsula, the dune field has remained largely unexplored owing to the harsh clime and difficult terrain. This study takes advantage of geospatial technology (interpolations, supervised classification, minimum focal statistic) to extract information from the data contained in global Digital Elevation Model (DEM)s, satellite imagery. The main objective here is to identify and map different dune forms within the sand sea, estimate the volume of sand and explore probable sources of sand. The analysis of dune color strongly suggests that the sand is not completely reworked and intermixed. If this is true, a spatial variability map of the mineral composition of the sand could be very revealing. The red sand is quite pronounced, the largest volume of sand (~36%) is associated with the yellow color class. Yellow sand covers most of the western part of the dunes field and seems to be a transitional color between red and white sand in the eastern part of the dune field. This suggests that the yellow sand might be derived from both local and regional sources, or it might be less oxidized, reworked, or have a different composition that represents a combination of red and white sand.

Source‐To‐Sink Aeolian Fluxes From Arid Landscape Dynamics in the Lut Desert

AbstractWe analyze major landforms of the Lut Desert in Iran to provide a comprehensive source‐to‐sink picture of aeolian systems on time scales from decades to millions of years. We map the modern sandflows, along which we evaluate the volume and chronology associated with the excavation of mega‐yardangs upwind and the formation of giant dunes downwind. Sediment discharges deduced from long‐term erosion and deposition are of the same order of magnitude (105–106 m3 yr−1) as short‐term and medium‐term sand discharges derived from wind data and dune morphodynamics. At the scale of the internal aeolian sediment‐routing system of the Lut, we establish an overall sediment budget constrained by the joint development of the erosional and depositional landforms. Our findings thus quantify the geomorphic controls of aeolian processes on arid landscapes at multiple length and time scales, while providing information on mass exchanges between continents and atmosphere.

ВЛИЯНИЕ ЭОЛОВЫХ ПРОЦЕССОВ (ФАКТОРА ВЕТРА) НА ФОРМИРОВАНИЕ И МОРФОЛОГИЮ РУСЕЛ И ПОЙМ РАВНИННЫХ РЕК1

The paper provides a generalized description of the influence of the eolian factor on channel processes in mouth areas of large and largest rivers. It is shown that the impact of wind manifests itself, firstly, in a change in the hydraulic structure of the flow, which leads to an increase or decrease in the surface velocity, transverse distortions of water surface, and level derivations due to up and down surges, causing flow backwater or an increase in slopes (level drop). Accordingly, this affects the development of erosion processes in the windward parts of the channel, accumulation of sediments and shallowing of the leeward parts, including channel branches located here, and the strengthening or weakening of bank erosion depending on the ratio of the vectors of the river flow and wind directions. Secondly, when channel sandy side-bars dry out in a low water period, the eolian process causes a deficit of sediments in the leeward part of the channel and their accumulation in the windward part, leading to its shallowing, as well as intensifying erosion of the island heads or accumulation of sediments in their tails. Thirdly, sand transported from the shoals is accumulated on the floodplain along its edge, forming dunes. The formation of dunes creates new conditions for the interaction of channel and floodplain flows during the flood period. Hydroclimatic changes in the late 20th - early 21st centuries contributed to the overgrowth of riverine shallows and dunes on the floodplain. Other forms of influence of eolian processes on river channels are also shown.

Late Pleistocene and Holocene aeolian activity in the Deliblato Sands, Serbia

AbstractThe Deliblato Sands is among the largest uniform dune fields of Europe, with a very pronounced topography reflecting extensive past aeolian events. Although lacking numerical age data, previous researchers have hypothesized various periods of dune formation. Our research goals were to map the main morphological units of the Deliblato Sands, and to provide the first optically stimulated luminescence (OSL) ages for the major dune types. Mapping was carried out using digital elevation models, satellite images, and GPS profiles. Dune development was investigated using OSL. Several tests were performed concerning thermal treatment, signal characteristics, dose recovery, and dose distributions to assess the suitability of sediments for luminescence dating. Based on our results, two dune generations could be identified that differed in morphology and age. Older dune forms are primarily low sand-supply, hairpin-like parabolic dunes that developed from the last glacial maximum until the end of the early Holocene, then became stabilized. Younger, superimposed parabolic dunes record an intensive aeolian signal from the eighteenth and nineteenth centuries. The history of the Deliblato Sands fits with those from other European sand dune areas, and provides further details to understand paleoenvironmental changes in the region.

Mechanisms of land degradation and their environmental implications in a middle‐latitude desert area of China

AbstractThe movement of aeolian materials and dynamics of dune landforms are results of the transportation and accumulation of sandy sediments under the influence of climate, in which the processes that gave birth to sand dune formations are complex as the arid area has experienced different periods of humidity and aridity. These dynamics are still not well understood at present, especially at the inter‐decadal time scale. Based on a comprehensive analysis of geomorphological, sedimentological, geochemical, and ecohydrological data, this study discussed the dynamical changes of different dune landforms during the past half‐century and their formation mechanism in the Hexi Corridor, northern China. The results show that on the inter‐annual and inter‐decadal scales, the crescent‐shaped dunes move the fastest among different dune types. Dunes in Minqin move the fastest (at 6.2 ± 0.5 m yr−1) and dunes in Dunhuang move the slowest (at 0.8 ± 0.2 m yr−1). The dune sands are mainly medium sand (21.7%–57.4%) and fine sand (23.2%–53.0%) with an average grain size of 0.07 ± 0.01 mm ~0.24 ± 0.06 mm, similar to the world's average particle size of sand dunes. Annual precipitation and spring precipitation, annual average wind speed, and number of annual strong wind days are the main factors affecting the dynamic changes of dunes in the Corridor, indicating a major influence of climatic factors. STC (sufficient transport capacity) is evidenced for both the western and eastern Hexi Corridor, however, SSS (sufficient sand supply) and SA (sand availability) are the favourable factor for dune formation in the east part but is the limiting factor for the west. In the past half‐century, although the vulnerability of land degradation is a function of climate change, geomorphological processes, and anthropogenic pressure in the Hexi Corridor, water resource limitations have been more important.

Contribution of Lake-Dune Patterning to the Dune Height of Mega-Dunes in the Badain Jaran Sand Sea, Northern China

Mega-dunes in the lake group area of the Badain Jaran Sand Sea, China, are generally taller than dunes in the non-lake group area. This spatial distribution of dune heights may provide a new perspective on the controversy regarding the dunes’ formation mechanism. In this study, we calculated the relative heights and slopes of individual dunes based on a digital elevation model, and we confirmed the height distribution of abnormally tall dunes in the lake group area of the sand sea. It was also found that slopes of more than 10° in the lake group area are more common than those in the non-lake group area. Based on meteorological observations, coupled with the measurement of water content in the sand layers, we propose a conceptual model demonstrating that moisture exchange between the lakes and soil via non-rainfall water will humidify dune slopes and form a more favorable accumulation environment for aeolian sand, thus increasing dune heights. Although long-term observations are yet to be carried out, the present study can be used as evidence for understanding the basis of dune formation in the lake group area and assessing groundwater utilization in deserts.

Transformation of baroclinic tidal waves in the conditions of the shelf of the Far Eastern seas

This work is devoted to the study of the regimes of transformation of baroclinic tidal waves under the conditions of the Far Eastern seas within the framework of a fully nonlinear numerical model. Two sections were selected to study the features of wave dynamics – in the Sea of Okhotsk (Sakhalin Island shelf) and in the Bering Sea (near Cape Navarin). On the basis of the performed calculations, regional and seasonal features of the transformation of baroclinic waves and the structure of the flow induced by them were revealed. It is shown that the dynamics in the winter season is less intensive. The rotation effect on the formation of solibore in the studied conditions is analyzed. The obtained estimates of wave amplitudes and velocities are consistent with the published data of field observations in the Sea of Okhotsk. For the Bering Sea, the conditions are shown to be favorable for the generation of intensive internal waves, which indirectly confirms the hypothesis of influence of such waves on the formation of underwater sand dunes.

Ground-Penetrating Radar Prospections to Image the Inner Structure of Coastal Dunes at Sites Characterized by Erosion and Accretion (Northern Tuscany, Italy)

In this study we aimed to gain insights into dune formation and evolution from select coastal tracts of Northern Tuscany by inspecting their internal sedimentary architecture with Ground-Penetrating Radar (GPR) analysis. Erosion, equilibrium and accretion characterize the selected coastal tracts, and this analysis remarks on some GPR features consistently associated with specific coastal evolution states. A standard sequence of data processing made it possible to trace several radar surfaces and reflectors in the GPR profile, eventually interpreted in terms of depositional processes and erosive events. The stable or currently accreting coastal sectors show radar features compatible with a general beach progradation process, punctuated by berm formation in the general context of a positive sedimentary budget. Additionally, the radar facies distribution locally supports a mechanism of dune nucleation on an abandoned berm. Conversely, the GPR profile of the coastal sector today affected by erosion shows how a negative sedimentary budget inhibited coastal progradation and favored destructive events. These events interacted also with the active dunes, as demonstrated by the overlapping of wave run-up and aeolian radar facies. GPR prospections were effective at delineating the recent/ongoing coastal sedimentary budget by identifying radar features linked to construction/destruction phenomena in the backshore, and to dune nucleation/evolution.

Blowing the rivers: Regional-scale control of the drainage network by wind in northern Kalahari (Africa)

Understanding the impact of aeolian processes on the regional-scale dynamics of fluvial systems in semi-arid regions is a major issue in the framework of climate change. Although the interactions between aeolian and fluvial processes have been studied on a meter to kilometer scale, few studies have upscaled to the regional scale. Using satellite images and SRTM-1 digital elevation models we document the formation of parabolic dunes and foredunes along the main rivers of the southern Angolan Plateau and northern Kalahari Basin (Africa). We demonstrate that these aeolian features derive from interactions between the morphology of the drainage system, the wind pattern, the vegetation cover and the transport capacity of the rivers. As a retro-action phenomenon, the progradation of parabolic dune fields induces tens-of-kilometers shifting in rivers courses in the northern Kalahari basin. The mechanism proposed has implications in terms of fluvial dynamics, river capture, geometry of clastic deposits in basins or source-to-sink budget.

Geomorphology of the Tafilalt Basin, South-East Morocco – implications for fluvial–aeolian dynamics and wind regimes

ABSTRACT The hyper-arid Taflilat Basin, South-East Morocco, is dominated by two ephemeral fluvial networks and several ergs with various dune forms from barchans to mega dunes. Especially the genesis of the star dunes remains an open research question. Therefore, a new multi-sheet geomorphological map describes the surface dynamics in the basin. Identification of major surface features was done with remote sensing data and on-site surveys. The analyses were used to identify all different landscape units. Additionally, aeolian features are emphasized to deduce current wind directions. The identification of two opposite wind fields was possible and a spatial correlation in the fluvial-aeolian system is detected. The border of the opposite wind fields crosses Erg Chebbi. Hence, the star dunes are under the influence of a multimodal wind system. Overall, this new geomorphological map strengthens the understanding of the fluvial-aeolian interaction in the Tafilalt Basin and sets a baseline for ongoing in-depth studies.

Formation of parabolic dunes on the shore of Poyang Lake in East China

Parabolic dunes can transform from and into other types of dunes in response to environmental changes. The sand hills, including some parabolic dunes, on the shore of Poyang Lake mainly accumulated during the Last Glaciation and are rare inland aeolian landforms in the humid monsoon climate zone in East China. However, the characteristics, distribution and formation of the parabolic dunes in this region are still not clear. Three sand hills with similar scales and wind regimes at Shaling, Jishan and Songmenshan were selected as the research targets. Integrating topographical, hydrological, vegetation and wind data, we found that the development of the parabolic dunes was effectively controlled by both the vegetation cover of the sand hills and the space available downwind of the sand hills. No parabolic dunes were found at Songmenshan and Shaling; the former has too little vegetation cover, favouring the formation of blowouts, and the latter lacks available space since Shaling is surrounded by villages and farmlands. Three types of parabolic dunes that developed sequentially in the downwind direction, namely, type A, type B and type C dunes, are observed at Jishan, and their formation is related to a narrowly unimodal and high-energy wind regime. Different from existing models, type A dunes are found to originate from the wedge-shaped depositional lobes of trough blowouts; type B dunes transform from type A dunes after migration; and type C dunes develop from very low sand drifts. Composite parabolic dunes are formed when the sand supply is plentiful, while simple parabolic dunes appear when the sand supply is limited. The formation of the parabolic dunes occurred approximately 250 years ago, which is close to the documented time when the sand hills were reactivated due to the vegetation being anthropogenically damaged. Therefore, anthropogenic destruction of vegetation is a trigger for producing parabolic dunes in this humid area. This study may shed light on the evolution of aeolian landforms in humid monsoon climate zones.

Tectonic, hydrogeologic, and climatic controls on Late Holocene dune formation, China Lake basin, Indian Wells Valley, California, USA

AbstractAnalysis of patterns of faulting and hydrogeology, stratigraphic and sedimentologic studies, and luminescence dating of aeolian deposits in China Lake basin provide new perspectives on the origins and development of Late Holocene dunes and sand ramps in the seismically active Indian Wells Valley of eastern California. Aeolian dune and sand sheet deposits were sourced from alluvial material derived from granitic rocks of the south-eastern Sierra Nevada and are concentrated in areas with sand-stabilizing phreatophyte vegetation influenced by high groundwater levels along the active oblique-normal Little Lake and Paxton Ranch faults, which locally form barriers to groundwater flow. Three episodes of sand accumulation are recognized (2.1 ± 0.1 to 2.0 ± 0.1 ka, 1.8 ± 0.2 to 1.6 ± 0.2 ka, and 1.2 ± 0.1 to 0.9 ± 0.1 ka) during conditions in which sediment supplied to the basin during periods of enhanced rainfall and runoff was subsequently reworked by wind into dunes and sand ramps at the transition to more arid periods. Understanding the role tectonics plays in influencing the hydrogeology of seismically active lake basins provides insights to accurately interpret landscape evolution and any inferences made on past hydroclimate variability in a region.

The Formation of Late Pleistocene and Holocene Sand Dunes on Kikaijima Island, Nansei Islands

Coastal sand dunes dating to the latter part of the late Pleistocene were constructed at substantially lower sea levels on Kikaijima Island. They are preserved because of large-magnitude uplifts ascertained from occurrences of outstanding late Pleistocene and Holocene coral terraces. In addition, because Holocene sand dunes occur close to those of Marine Oxygen Isotope Stage 3 (MIS 3), the island is ideal for examining the environments of the formation of sand dunes, which were constructed under different climatic and sea-level conditions. Distributional and depositional features of sand dunes are clarified, and their chronology is constructed on the basis of tephrochronology, 14C dating, and chronological relationships of the sand dunes with marine terraces of known age. The environments of sand-dune formation on Kikaijima are examined in relation to climatic and sea-level records within regional and global contexts. Nine tephra layers are recognized. These include two widespread tephras, Kikai-Akahoya tephra (K-Ah) and Aira-Tn tephra (AT). The other seven tephras, consisting of fine ash layers, are newly recognized and named Kikaijima-1 tephra (Kj-1) to Kikaijima-7 tephra (Kj-7), of which the upper six, lying between K-Ah and AT, are aged from 13,000 to 30,000 cal BP. Holocene sand dunes began to form at c. 8,000 cal BP before the culmination of maximum Holocene sea-level rise. This is earlier than dune formation on other coasts of the Japanese Islands, where formation was generally after the culmination of maximum Holocene sea-level rise. The earlier formation on Kikaijima Island is probably due to coastal emergence caused by the conspicuous uplifts of Kikaijima and the high production of calcareous beach sands sourced from coral and foraminiferal and other materials. Late Pleistocene sand dunes, predominantly distributed at the southwestern part of Kikaijima Island, were formed in MIS 3. These dunes consist of longitudinal and parallel dunes. The largest longitudinal dunes on the lowest MIS 3 terraces, at the northern area of the southwestern part of Kikaijima Island, were formed in late MIS 3, c. 40 to 32 ka, while small and parallel sand dunes on the upper MIS 3 terraces were formed in early MIS 3. The occurrence and chronology of the Holocene and late Pleistocene sand dunes suggest that their formation on Kikaijima Island is mainly related to the occurrence of coastal sandy beaches during sea-level high stands. Although Holocene sand dunes are related to Holocene high stand, those of MIS 3 are related to high stands during cycles of sea-level fluctuations in MIS 3. The longitudinal landform of the sand dunes recognized in the late MIS 3 suggests that the prevailing winds in MIS 3 were stronger than in the Holocene. This study provides critical data for constructing a chronological framework that integrates various aspects of palaeoenvironments, as well as human interactions and responses in southern Kyushu.

Uneven surface moisture as a driver of dune formation on ephemeral lake beds under conditions similar to the present day: A model‐based assessment from the Makgadikgadi Basin, northern Botswana

AbstractAn association between salt pans or dry lake beds and distinctive crescentic lake‐floor sand mounds (1–10 m high, tens to hundreds of metres wide) is commonplace in desert systems. In the Makgadikgadi Basin of northern Botswana, a debate about the formative processes of these landforms has persisted despite numerous morphometric, sedimentary and geochronological analyses, with mound landforms variously inferred to be aeolian dunes, subaqueous dunes, spring mounds or shoreline remnants. We propose a new formative mechanism which draws on the interaction between uneven moisture distribution on the pan surface and mobile aeolian sediments. We use a numerical model (ViSTA), which couples vegetation and aeolian sand transport dynamics, together with optically stimulated luminescence (OSL) dating of a mound in the Makgadikgadi Basin to investigate the feasibility of this ‘sticky mound hypothesis’. We find that under a range of modelled environmental conditions, uneven moisture distribution on the pan surface can lead to the development and stabilization of crescentic aeolian dunes, with these dunes growing upwind from the point of initial deposition, corresponding with the chronological data gained from OSL dating of a mound feature. On removal of this moisture, the modelled dunes erode and dissipate. These findings suggest that the formative mechanism of the mounds could be dependent on the interaction between differential drying of the pan surface and the competence of the aeolian sediment transport system across the pan floor.

Mid-late Holocene climatic reconstruction from coastal dunes of the western Kachchh, India

The present study focuses on the mechanism, climate, and sea-level implications of the coastal dune building activity in the eastern coast of Kori Creek (Gulf of Kachchh). Around 10 m thick dune is investigated using sedimentology, geochemistry, and optical chronology. This study suggests that the dune sediment that overlies the Tertiary Oyster Bed is dated to ∼4 ka. The grain size analysis and correlation of textural parameters of the inland dunes and coastal dunes showed no stark difference, revealing they were deposited during the same time. Further, the geochemical data generated from the samples of the coastal dune site represent semi-arid to semi-humid climate with increasing chemical maturity and weakening monsoon during the time of deposition. Based on the current erosion dune face and optical ages of the samples, it can be related that the Kachchh coastline was exposed due to the lowering of the sea level at the time of the deposition of coastal dunes. The sea must be at a lower level to attain a preferable condition for the deposition of dunal landforms. The lowering of the sea exposed the beach with sandy material, which got blown away in strong wind, leading to dunes deposition. The cold phase at ∼4.2ka became the most conducive environment of coastal dune formation.

Aeolian processes and landforms

Abstract A number of major factors have driven the volume and nature of aeolian geomorphology in the second half of the twentieth century: the growth of process studies; the availability of remote sensing, the development of new dating techniques (e.g. optical dating), the utilization of new technologies (e.g. data loggers and global positioning systems); computer modelling of dune forms, wind action and sediment movement; the recognition of the importance of aeolian forms and processes in extraterrestrial settings (especially Mars); the role of aeolian dust in atmospheric processes; the search for analogues for ancient hydrocarbon-bearing strata; the appreciation of the importance of climatic changes in desert areas; a concern with what may happen to arid environments in a warmer world; and an increasing realization that aeolian phenomena could be hazardous. This chapter does not deal with coastal dunes, but concentrates on those of the major lower-latitude drylands. It discusses the main controls on dune forms, the nature of sand seas, ancient and modern, and the nature of dune sediments. It also shows that during the 1970s there was a burgeoning interest in dust storms. In addition, with the availability of remote sensing imagery, it was possible to see for the first time that wind-furrowed yardangs were striking features with a wide global distribution. The origin of closed depressions (pans) generated a large literature, and hypotheses for their formation were put forward that included wind erosion, solution, excavation by animals, karstic and pseudo-karstic solution, and tectonic subsidence. Remote sensing showed just how important they were in drylands. Other phenomena that attracted attention and some controversy were stone pavements and peri-desert loess. Finally, it is suggested that the nature of aeolian processes and forms will be modified in a warmer world.

Linear stability of sand waves sheared by a turbulent flow

In this paper, the linear stability of sand waves sheared by a turbulent flow is analyzed. The velocity distribution in the streamwise direction is considered to follow the logarithmic law. The modified pressure distribution owing to the streamline curvature induced by the sand waves is employed in the formulation. The pressure distribution is derived using the Boussinesq approximation for the variation of streamline curvature over the flow depth. The flow model is coupled with the sediment transport model to study the stability of sand waves. Both the modes of sediment transport as bedload and suspended load are considered. The linear stability analysis reveals the favorable region for the formation of dunes and antidunes on the plane formed by the Froude number and the dimensionless wavenumber. The region of instability increases with an increase in particle parameter, while it decreases with an increase in relative roughness. The analysis reveals that the sand waves form beyond a limiting Froude number corresponding to the threshold Shields number. The theoretical results compare well with the available experimental data.

Stratigraphic and sedimentologic investigation of collapse features in the Mount Baldy Dune in the Indiana Dunes National Park

Mount Baldy dune is one of the largest active eolian dunes along the southern shore of Lake Michigan and a famous tourist attraction within the Indiana Dunes National Park. It is an anthropogenically disturbed landform where restoration efforts include native beach-grass plantings and restricted foot traffic. In July 2013, a 6-year-old boy was buried more than 3 m below the dune stoss surface after falling into a hole, or “collapse feature.” While previous work indicated that holes formed through the decay of buried oak trees (Quercus spp.), neither the origin of this hole in relation to the dune’s stratigraphy nor its significance as a potential geological hazard were understood. Groundpenetrating radar, sediment cores, and radiocarbon and optically stimulated luminescence dates were collected to define sedimentary packages and facies, and interpret the dune’s depositional history. The data show that an alongshore migrating coastal dune field stabilized ∼3000 ya atop backbarrier lagoonal deposits. Modern Mount Baldy evolved as sands were mobilized and transported onshore over the relict dune field, triggered by ongoing downdrift coastal erosion related to the development of the Michigan City Harbor. The internal architecture of the dune reveals how the topography of the forested landscape, now buried beneath the modern dune form, contributes to variations in the thickness of the upper dune package, controlling the relation of buried and decayed trees to the surface of the stoss slope. The data on sand thicknesses, were used with maps and aerial photographs to create a geohazard map of the dune.