A Holocene history of dune-mediated landscape change along the southeastern shore of Lake Superior     

Walter L. Loope  Timothy G. Fisher  Harry M. Jol  Ronald J. Goble  John B. Anderton  William L. Blewett 《Geomorphology》2004,61(3-4):303-322

Causal links that connect Holocene high stands of Lake Superior with dune building, stream damming and diversion and reservoir impoundment and infilling are inferred from a multidisciplinary investigation of a small watershed along the SE shore of Lake Superior. Radiocarbon ages of wood fragments from in-place stumps and soil O horizons, recovered from the bottom of 300-ha Grand Sable Lake, suggest that the near-shore inland lake was formed during multiple episodes of late Holocene dune damming of ancestral Sable Creek. Forest drownings at 3000, 1530, and 300 cal. years BP are highly correlated with local soil burial events that occurred during high stands of Lake Superior. During these and earlier events, Sable Creek was diverted onto eastward-graded late Pleistocene meltwater terraces. Ground penetrating radar (GPR) reveals the early Holocene valley of Sable Creek (now filled) and its constituent sedimentary structures. Near-planar paleosols, identified with GPR, suggest two repeating modes of landscape evolution mediated by levels of Lake Superior. High lake stands drove stream damming, reservoir impoundment, and eolian infilling of impoundments. Falling Lake Superior levels brought decreased sand supply to dune dams and lowered stream base level. These latter factors promoted stream piracy, breaching of dune dams, and aerial exposure and forestation of infilled lakebeds. The bathymetry of Grand Sable Lake suggests that its shoreline configuration and depth varied in response to events of dune damming and subsequent dam breaching. The interrelated late Holocene events apparent in this study area suggest that variations in lake level have imposed complex hydrologic and geomorphic signatures on upper Great Lakes coasts.  相似文献   

Investigating dune-building feedback at the plant level: Insights from a multispecies field experiment     

Elsemarie Mullins  Laura J. Moore  Evan B. Goldstein  Theo Jass  John Bruno  Orencio Durán Vinent 《地球表面变化过程与地形》2019,44(9):1734-1747

Coastal foredunes provide the first line of defense against rising sea levels and storm surge and for this reason there is increasing interest in understanding and modeling foredune formation and post-storm recovery. However, there is limited observational data available to provide empirical guidance for the development of model parameterizations. To provide guidance for improved representation of dune grass growth in models, we conducted a two-year multi-species transplant experiment on Hog Island, VA, U.S.A. and measured the dependence of plant growth on elevation and distance from the shoreline, as well as the relationship between plant growth and sand accumulation. We tracked total leaf growth (length) and aboveground leaf length and found that Ammophila breviligulata (American beachgrass) and Uniola paniculata (sea oats) grew more than Spartina patens (saltmeadow cordgrass) by a factor of 15% (though not statistically significant) and 45%, respectively. Our results also suggest a range of basal/frontal area ratios (an important model parameter) from 0.5-1 and a strong correlation between transplant growth and total sand deposition for all species at the scale of two years, but not over shorter temporal scales. Distance from the shoreline and elevation had no effect on transplant growth rate but did have an effect on survival. Based on transplant survival, the seaward limit of vegetation at the end of the experiment was approximately 30 m from the MHWL and at an elevation of 1.43 m, corresponding to inundation less than 7.5% of the time according to total water level calculations. Results from this experiment provide evidence for the dune-building capacity of all three species, suggesting S. patens is not a maintainer species, as previously thought, but rather a moderate dune builder even though its growth is less stimulated by sand deposition than A. breviligulata and U. paniculata. © 2019 John Wiley & Sons, Ltd.  相似文献   

Two-dimensional time dependent hurricane overwash and erosion modeling at Santa Rosa Island     

R.T. McCall  J.S.M. Van Thiel de Vries  N.G. Plant  A.R. Van Dongeren  J.A. Roelvink  D.M. Thompson  A.J.H.M. Reniers 《Coastal Engineering》2010

A 2DH numerical, model which is capable of computing nearshore circulation and morphodynamics, including dune erosion, breaching and overwash, is used to simulate overwash caused by Hurricane Ivan (2004) on a barrier island. The model is forced using parametric wave and surge time series based on field data and large-scale numerical model results. The model predicted beach face and dune erosion reasonably well as well as the development of washover fans. Furthermore, the model demonstrated considerable quantitative skill (upwards of 66% of variance explained, maximum bias − 0.21 m) in hindcasting the post-storm shape and elevation of the subaerial barrier island when a sheet flow sediment transport limiter was applied. The prediction skill ranged between 0.66 and 0.77 in a series of sensitivity tests in which several hydraulic forcing parameters were varied. The sensitivity studies showed that the variations in the incident wave height and wave period affected the entire simulated island morphology while variations in the surge level gradient between the ocean and back barrier bay affected the amount of deposition on the back barrier and in the back barrier bay. The model sensitivity to the sheet flow sediment transport limiter, which served as a proxy for unknown factors controlling the resistance to erosion, was significantly greater than the sensitivity to the hydraulic forcing parameters. If no limiter was applied the simulated morphological response of the barrier island was an order of magnitude greater than the measured morphological response.  相似文献   

Modelling storm impacts on beaches, dunes and barrier islands   总被引：10，自引：0，他引：10  

Dano Roelvink  Ad Reniers  Ap van Dongeren  Jaap van Thiel de Vries  Robert McCall  Jamie Lescinski 《Coastal Engineering》2009,56(11-12):1133-1152

A new nearshore numerical model approach to assess the natural coastal response during time-varying storm and hurricane conditions, including dune erosion, overwash and breaching, is validated with a series of analytical, laboratory and field test cases. Innovations include a non-stationary wave driver with directional spreading to account for wave-group generated surf and swash motions and an avalanching mechanism providing a smooth and robust solution for slumping of sand during dune erosion. The model performs well in different situations including dune erosion, overwash and breaching with specific emphasis on swash dynamics, avalanching and 2DH effects; these situations are all modelled using a standard set of parameter settings. The results show the importance of infragravity waves in extending the reach of the resolved processes to the dune front. The simple approach to account for slumping of the dune face by avalanching makes the model easily applicable in two dimensions and applying the same settings good results are obtained both for dune erosion and breaching.  相似文献   

Rare earth elements of the Altar Desert dune and coastal sands, Northwestern Mexico     

Juan Jos Kasper-Zubillaga  Beatriz Acevedo-Vargas  Ofelia Morton Bermea  Glicinia Ortiz Zamora 《Chemie der Erde / Geochemistry》2008,68(1):45-59

Twenty-one surficial sand samples from the Altar Desert coastal and desert dune systems were analysed for rare earth elements (REE) content. This was done to observe the provenance signatures for four strategic dune localities near the Colorado River Delta, the El Pinacate dune fields, and the beaches of the north of the Gulf of California in the state of Sonora, Mexico. Our goals are to show which mechanisms (i.e., aeolian, marine) exert more influence on the composition of the Altar Desert dune sands. This study also shows the usefulness of REE spatial distribution to determine the relative mobility of the sand. Some sand samples from the dune systems in San Luis Río Colorado (SLRC), Golfo de Santa Clara (GSC), and Puerto Peñasco (PP) displayed dissimilar REE concentrations with respect to the rest of the sand samples from the same sites. These differences can be related to short aeolian transport distance in the sands with high REE concentrations and long aeolian transport distance in the sands with low REE concentrations. Besides, high REE concentration in the sands might be due to their closeness to the Colorado River Delta sediments and to recycled sands derived from granitic rocks. In contrast, all the sand samples from the El Pinacate (EP) site have similar REE concentration values, suggesting that the El Pinacate dune sands are influenced by more selective aeolian processes and less diverse heavy mineral content. The Altar Desert dune sands are derived from granitic sources eroded by the Colorado River. Our results also indicate that the Altar Desert dune sands are low in heavy mineral content (with the exception of Fe and Ti bearing minerals) and enriched in carbonates with phosphates (especially at the PP site) yielding poor correlations between REE and major element concentrations. The REE geographical distribution values in the Altar Desert dune sands indicate that light and heavy REE concentration values are related to aeolian transport, maturity of the sands, their low weathering rates, proximity of the source rocks, and the biogenic debris input from beach sands into the dune.  相似文献   

Elongation and migration of sand dunes   总被引：3，自引：0，他引：3  

Haim Tsoar  Dan G. Blumberg  Yoav Stoler 《Geomorphology》2004,57(3-4):293-302

Two distinct processes are known to act on dynamic dunes, the process of migration by erosion on the windward side and deposition on the lee side, typical for transverse dunes, and the process of elongation typical for linear dunes. These two processes are determined by wind direction relative to the dune alignment. This article reviews the assertion that linear dunes experience lateral displacement in addition to elongation. Fieldwork on vegetated linear dunes (VLDs) and GIS work on seif dunes indicates no lateral migration for these dunes. Linear dunes can shift laterally only when a slip face, formed on the lee side, reaches the plinth of the dune. The winds from both sides of the seif dune are never symmetric; usually winds from one direction are more dominant and effective. The outcome is the formation of peaks and saddles along the dune. The strongest winds create a slip face on the lee side of the peak segments of the dune, oblique to the dune alignment, which reaches the base of the dune and displaces the peak downwind along the dune alignment. The internal structure of the seif dune is formed mostly by this dominant wind direction and gives the impression that the dune has shifted laterally. On the other hand, there are cases in which the wind directions relative to dune alignment fall between those of transverse and seif dunes. In such cases, both processes act on the dune, which subsequently experiences migration as well as elongation.  相似文献   

Variations of horizontal and vertical velocities over two-dimensional transverse dunes: A wind tunnel simulation of the effect of windward slope   总被引：2，自引：0，他引：2  

G. Qian  Z. Dong  W. Luo  H. Wang 《Journal of Arid Environments》2009,73(12):1109-1116

The changes in wind velocity induced by dune topography have an important significance in dune dynamics. In this paper, the horizontal and vertical velocities over six transverse dune models were measured non-intrusively by means of Particle Image Velocimetry in a wind tunnel. The windward slope angle and the free-stream wind velocity both affected the horizontal and vertical velocity components. On the windward side, the acceleration of horizontal velocity depended mainly on the windward slope angle and the height above the dune surface, but was also affected by the free-stream wind velocity. The speed-up ratio increased with increasing slope angle but decreased with increasing height. The ascending vertical velocities also increased with increasing slope angle and free-stream wind velocity. The maximum values moved upper along the dune when the windward angle became steeper. In the leeward sides, the horizontal velocity decreased and reversed because of airflow separation; the maximum reverse velocity in the separation cell was about 17% of the free-stream wind velocity. Behind the dune crest, the airflow moves downwards, and its maximum downward velocity is found near the flow reattachment point. Finally, we discussed the significance of these velocity variations for sediment transport and dune dynamics.  相似文献   

Episodic Late Holocene dune movements on the sand-sheet area, Great Sand Dunes National Park and Preserve, San Luis Valley, Colorado, USA     

S.L. Forman  M. Spaeth  J. Pierson  F. Bunch 《Quaternary Research》2006,66(1):97-108

The Great Sand Dunes National Park and Preserve (GSDNPP) in the San Luis Valley, Colorado, contains a variety of eolian landforms that reflect Holocene drought variability. The most spectacular is a dune mass banked against the Sangre de Cristo Mountains, which is fronted by an extensive sand sheet with stabilized parabolic dunes. Stratigraphic exposures of parabolic dunes and associated luminescence dating of quartz grains by single-aliquot regeneration (SAR) protocols indicate eolian deposition of unknown magnitude occurred ca. 1290-940, 715 ± 80, 320 ± 30, and 200-120 yr ago and in the 20th century. There are 11 drought intervals inferred from the tree-ring record in the past 1300 yr at GSDNPP potentially associated with dune movement, though only five eolian depositional events are currently recognized in the stratigraphic record. There is evidence for eolian transport associated with dune movement in the 13th century, which may coincide with the “Great Drought”, a 26-yr-long dry interval identified in the tree ring record, and associated with migration of Anasazi people from the Four Corners areas to wetter areas in southern New Mexico. This nascent chronology indicates that the transport of eolian sand across San Luis Valley was episodic in the late Holocene with appreciable dune migration in the 8th, 10-13th, and 19th centuries, which ultimately nourished the dune mass against the Sangre de Cristo Mountains.  相似文献   

敦煌莫高窟窟顶沙丘移动的初步研究   总被引：7，自引：0，他引：7  

屈建军  苗天宝 《甘肃地质》1995,4(2):87-93

通过窟顶风沙资料的理论计算和沙丘动态监测，首次提出了窟顶沙丘移动方向为ＳＷ→ＮＥ向，移动方式为盘旋式－慢速稳定型。窟顶沙丘年平均移动量０．４２ｍ／ａ，入窟沙量４２９１ｍ￣３。在近百年内，沙丘不会埋没洞窟，但风沙流的危害仍十分严重。因此防止窟顶风沙流的危害是目前石窟保护中急待解决的重要问题。  相似文献   

Heinrich events recorded in a loess-paleosol sequence from Hexigten,Inner Mongolia     

Ji-Ling Song  Hong-Yan Sun  Ming-Zhong Tian  Xu-Jiao Zhang  Xue-Feng Wen  Miao Sun 《地学前缘(英文版)》2018,9(2):431-439

We describe the last glaciation climatic history Marine Isotope Stage(MIS, 2-4) from 66.7 ka to 14.5 ka in Hexigten, northeast Inner Mongolia, North China. The climate of the region experienced frequent and significant fluctuations between dry-cold and less dry-cold during the late MIS4. The climate was generally warm and humid during early MIS3(MIS3 c) and late MIS3(MIS3 a), whereas it was cold and dry in middle MIS3(MIS3 b) and during MIS2. In this study, the cold and dry conditions were correlated with a stronger East Asian winter monsoon and strong dune activity; whereas, warm and humid conditions were related to a stronger East Asian summer monsoon(EASM) and weak dune activity. This study establishes six distinct dry and cold intervals during the last glacial period(66.7-14.5 ka) based on optically stimulated luminescence data, multi-proxies record(magnetic susceptibility, grain size analysis, Rb/Sr, SiO2/TiO2) and chemical index of alteration(CIA). The last glacial period may be correlated with Heinrich events 1 to 6 which were further confirmed by comparison with the Hulu cave stalagmites and Greenland ice core records. It is concluded that the study area was substantially affected by the EASM, as compared with the loess-desert transition zone of the Chinese Loess Plateau, especially in MIS3 c and suggested that the East Asian monsoon played a pivotal role in the last glacial period climate and dune activity.  相似文献