Aeolian sedimentology

The stop (24°50'2"E, 57°10'15"N, for location see Fig. .1) at the Krimulda Castle ruins in Sigulda introduces the geological structure, morphology and formation of the River Gauja valley and slope processes between the towns of Valmiera and Vangaži. This stretch of the river valley, also known as the Lower Gauja spillway valley, is about 110 km long. The spillway is confined to an ancient buried valley incised into Middle and Upper Devonian sedimentary rock (Pērkons 1947). The oversized river valley is 1-2.5 km wide and reaches a depth of 25 m near Valmiera, 35-40 m in the vicinity of Cēsis and 85 m at Sigulda. The floor of the bedrock within the valley lies at 17-18 m a.s.l. near Valmiera, 12 m b.s.l. in the vicinity of Cēsis and more than 50 m b.s.l. at Sigulda (Fig. 1.2). It is significant that downstream of Cēsis the ancient valley is carved into weakly-cemented and/or soft Devonian terrigenous rock that runs along the lithological boundary with carbonate rock.

ABSTRACTArcuate mud‐drapes have been observed in an interdune area in southern Tunisia. They are believed to have been formed by deposition from ponded water around aeolian dunes during flood events. They are preferentially preserved on the stoss‐side of the dunes as a result of subsequent dune migration, and exhibit extensive evidence of animal tracks. They are useful in illustrating dune‐interdune dynamics and recording the type of animals present.

Dunefields are very common in the northern coastal zone of northeast Brazil. They have the potential to yield important information about paleoclimate, paleo-winds and regional winds and their response to sea-level fluctuations during the Holocene. We reconstructed the coastal dunes geochronological evolution of northwest Ceará State -Brazil, in the last 3000 cal yrs BP, using detailed analyses of lithostratigraphy, microfossil (foraminifera), wind regime, dune monitoring and 8 radiocarbon dates. The chronology was based on 14 C dating in eolianites and monitoring transversal mobile dunes movement processes. Radiocarbon date results indicated that the dunes corresponding to eolianites revealed ages between 2760-2480 and 980-750 cal yrs BP, suggesting that the vast transversal mobile dunefields were formed after this period in similar condition to the current sea-level. We considered that the material transportation by the prevailing east winds towards the transversal dunes is estimated in the order of 11.0 m/year, thus the current aeolian system is less than 1000 yrs BP.

The Upper Miocene-Lower Pliocene Río Negro Formation (Río Negro Province, Argentina) contains diverse and abundant continental trace fossils. The purpose of this contribution is to recognize distinctive trace fossil assemblages in interdune lakes as response to lake expansion and contraction. The interdune deposits host 23 invertebrate, vertebrate, and plant ichnotaxa that are linked to the hydrological dynamics of the lake. During lake expansion a highly diverse subaqueous trace fossil assemblage reflects an infaunal bivalve population living in a littoral zone with swampy vegetation and semiaquatic mammals. The trace fossil assemblage recorded during Lake Highstand is less diverse and mostly linked to bivalve-generated trace fossils reflecting resting, locomotion, and escape/equilibrium behaviour (comparable to the Mermia ichnofacies). The assemblage during lake contraction exhibits high ichnodiversity and is dominated by vertebrate trace fossils reflecting foraging activities of shorebirds, cursorial birds, and herding semiaquatic mammals and ground sloths frequenting water holes. Flat sandy areas with moist substrates marginal to the interdune lake displayed a moderate ichnodiversity and its distinctive components were armadillo meniscate burrows and footprints in cross-section, as well as subvertical calcareous root casts. Neogene interdune lacustrine deposits reflect a particular zonation of trace fossils in response to changing physical conditions.

My oral presentation at GEOHYDRO-2011 was at 11:00 am (Tues, Aug 30, 2011) in the session Quaternary Geology, Paleoenvironments and Geomorphology. After my power point presentation (30 slides) the floor was opened for questions. Colleagues who are doing similar geochronological dating work in Canada asked questions which essentially wanted to know about our methodological approaches and how they related to protocols they were using in their labs. In particular they wanted to know about the following: • what methods we use to normalize our samples (weight or irradiation) • what sources we use for irradiating our samples • if we have problems with signal contamination from feldspar when using post –IR blue-OSL stimulation with the portable OSL reader on bulk samples These were very constructive questions and, following my responses, I got some very interesting feedback. We will incorporate some of this feedback as we proceed with our research. Later during the conference I also had th...

The Great Salt Lake (Utah, USA) is reducing in size, which raises several ecological concerns, including the effect of an increasing area of dry playa exposed by the retreating lake. This study focuses solely on concerns about the toxicity of metals in the dust blowing off the playa. Although considerable efforts have been made to understand aeolian dust in urban areas along the Wasatch Front, located just east and south of the Great Salt Lake, there is still a need to consolidate existing research and to conduct a compositional analysis of the dust found in these urban areas. We investigated the dust reaching urban monitoring sites around the Great Salt Lake that are managed by the Utah Division of Air Quality. By analyzing historical data, we found that the decrease in the Great Salt Lake’s surface area has not led to a statistically significant increase in dust events in urban areas. Windrose plots align with prior research, indicating that heightened dust levels in urban areas coincide with winds originating from the south or west, passing over identified playas and deserts such as the Milford Flats, Sevier Dry Lake, Tule Dry Lake, Great Salt Lake Desert, Dugway Proving Grounds, and the West Desert of Utah. Metallic compositional analysis of urban dust was used to evaluate potential health risks associated with the dust using the hazard quotient, air regional screening levels, and cancer risk methods. This analysis revealed no significant increase in concentrations of toxic metals. However, this is not to preclude a risk of dust-related health concerns, especially due to pre-existing arsenic and lead levels.
Synopsis: This study provides insights into dust-related health risks and environmental impacts in Utah, analyzing dust exposure from shrinking Great Salt Lake.

Relict beach ridges of aeolian origin and associated soils are often used for inferring relative sea level and climate with contrasting results. Most studies link the aeolian coastal deposits to regressive phases, some to high sea-level stands, and a few to intermediate relative sea-level positions. We interpret the apparent contradictions as indicating the lack of an over-arching concept and the inconsistent usage of sea level-related terms. In this paper we present an integrated morpho-sedimentological concept for a microtidal, mid-latitudinal coast and review existing data from the Levant (East Mediterranean) coast to evaluate the concept and to eliminate nomenclatural confusion. A coastal depositional environment in a semi-arid environment consists of shallow-marine, aeolian and alluvial facies which together form an aeolian beach-ridge complex as a package of strata which respond simultaneously to sea-level change. A transgressive complex forms through reworking or overstepping of the coastal foredune and a regressive complex forms by downstepping. Under transgression the aeolian beach ridge represents the highstand deposit and its adjacent shallow marine sediment is the transgressive deposit. Under regression the complex represents the falling stage and the associated downdip surface marks the lowstand. On the Levant coast we find chronologically well-constrained, offlapping aeolian beach ridges as parts of six downstepping beach ridge complexes formed between ~200 ka and 10 ka. The complexes represent the falling stage systems tract (FSST) of a short-lived (5th-order) depositional sequence when the shoreline shifted from a position close to the modern coastline to the shelf or below the shelf edge. Three of these FSSTs and their up dip and down dip super bounding surface together form the 4th order (~100 ka) sequence of the last interglacial/glacial cycle. The absence of transgressive, highstand and lowstand systems tract is explained by the poor preservation potential due to the small sediment budget of the complex. The falling stage complex has a high preservation potential because sediment source area increases while the sand drift potential remains above the local threshold. On the Levant coast, sand delivery to the backshore continued during relative sea-level falls for distances of up to 10 km between dune and coastline which is unprecedented in most modern analogues. The significance of the dune-soil succession for climate is limited because the dunes are governed by relative sea-level change; the vegetation response to changes in precipitation is non-linear and the dune dynamics are characterised by low resilience and hysteresis.

Introduction. The predominance of aeolian (wind-driven) activity as a surface modifying agent on Mars has been recognized throughout the history of telescopic, satellite, and robotic investigation of the planet. The most obvious expressions of aeolian processes are manifested in dunes, yardangs (aerodynamic ridges in bedrock) [1,2], sand ripples [3,4], and Transverse Aeolian Ridges (TARs) [5]. TAR is a nongenetic general term proposed for linear to curvilinear aeolian features. Since their first recognition, the origin of TARs remains an area of healthy debate, are TARs small dunes or are they large ripples? The answer to this question is critical to understanding the way the wind works on the martian surface and this has implications for NASA strategic interests in area of sustained human and robotic exploration of Mars. The challenge is that to answer the questions of origin, we need to understand the details of shape, size, and spatiotemporal development of the bedforms, and the size and density of the grains that form them. Although the resolution of remotely sensed data improves rapidly, down to 25cm/pixel with HiRiSE, we are still not capable of resolving sediment-size distributions [6]. Until we can do this, our understanding of aeolian processes on Mars will remain limited to the few lander and rover sites. Thus, we still rely heavily on our understanding of similar features on Earth as analogs both in terms of form and process. Recent rover investigations of Martian TARs provide perhaps the most definitive data [7].

Negev erg of Egypt − Particle-size fractionation of eolian sand along the Sinai Email alerting services articles cite this article to receive free e-mail alerts when new www.gsapubs.org/cgi/alerts click Subscribe America Bulletin to subscribe to Geological Society of www.gsapubs.org/subscriptions/ click Permission request to contact GSA http://www.geosociety.org/pubs/copyrt.htm#gsa click official positions of the Society. citizenship, gender, religion, or political viewpoint. Opinions presented in this publication do not reflect presentation of diverse opinions and positions by scientists worldwide, regardless of their race, includes a reference to the article's full citation. GSA provides this and other forums for the the abstracts only of their articles on their own or their organization's Web site providing the posting to further education and science. This file may not be posted to any Web site, but authors may post works and to make unlimited copies of items in GSA's journals for noncommercial use in classrooms requests to GSA, to use a single figure, a single table, and/or a brief paragraph of text in subsequent their employment. Individual scientists are hereby granted permission, without fees or further

Au Sahel, l’érosion éolienne se développe particulièrement sur les surfaces cultivées. La présente étude vise : 1) à quantifier les résidus de culture sur les champs traditionnels pour en déterminer leurs impacts sur l’intensité des flux d’érosion éolienne ; 2) à déterminer le rôle de l’érosion éolienne dans le développement des croûtes d’érosion d’horizon B et à déterminer en retour l’impact de cet encroûtement sur le flux d’érosion éolienne ; 3) à tester le rôle que pourraient jouer des aménagements de type bandes enherbées sur des sols nus très sensibles. Six années de mesures de flux d’érosion éolienne ont été entreprises à Banizoumbou dans le sud-ouest du Niger. Celles-ci ont permis de montrer que les résidus de culture protègent la surface des champs de l’érosion éolienne pendant la saison sèche (janvier – avril) et la diminuent significativement (de plus de 3 fois) au début de la saison des pluies (mai – juillet). Cependant, en dessous d’un seuil de 100 kg.ha-1 de recouvremen...

Introduction: Dunes on Mars provide evidence of active and ancient aeolian processes and are critical for understanding the planet's stratigraphy and surface modification history. Active sand transport and ripple migration occurring on Mars has been observed using automated image feature correlation and change detection [1, 2, 3], but genetically-related Transverse Aeolian Ridges (TARs) [e.g., 1] appear to have been stationary over recent history. TARs are commonly imaged by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter (MRO), and our goal is to develop an efficient, automated mapping strategy for TARs to understand their spatial distribution, morphological characteristics, and processes of formation. Methodology: Mapping TARs and including information such as shape, crest spacing, sinuosity and surface albedo is challenging because of their small footprint in HiRISE images. TARs can be found over large areas, but are typically found in isolated patches. To obtain quantitative topographic information about TAR height and morphology, high-resolution (1 m/pixel) digital terrain models (DTMs) can be constructed from HiRISE stereo-image pairs [5] using ISIS and SOCET SET software. These stereophotogrammetry methods are based on featurematching and the algorithms often have difficulty retrieving three-dimensional (3D) information from smooth surfaces, subtle features, or contiguous ripple textures. TARs typically occupy only a small portion of any HiRISE image, which makes processing an entire DTM for these small features a time-consuming task. Likewise, the area and size of TAR bedforms are generally small and near the limit of detection with respect to the spatial resolution (~1 m/pixel) of the DTMs. Although height information is highly desirable for analysis, the pattern of ripple and TAR ridges seen from HiRISE images alone can reveal information about paleo-wind directions, which is important for understanding Martian climate. Our initial efforts to map TARs focused on manual digitization of TAR patterns and 3D profile extraction, but it became apparent that automated image processing tools would be better for mapping TARs. Various approaches have been taken to automatically map sand ripples in image data by automatic detection of ripple crest patterns [6] and dunes using supervised machine learning [7]. We initially tested techniques [6]

Wind erosion flux and dune front dynamic in Manga, SE Niger Anthropic and climate changes reduced the vegetation cover and induced dunes movement in South-east of Niger. This work aimed to characterize wind erosion on moving dunes of the Manga in Niger. Specially, it aimed to measure wind erosion flux and to determine the velocity of the dunes fronts dynamics and the optimal period of their movement. Thus, an automatic meteorological station is installed in the village of Kilakina to direction and velocity of wind and rainfall. Metallic pickets have been installed in front of 22 dunes to measure theirs dynamics. And 3 masts of BSNE sand catcher have been installed to characterize wind erosion horizontal flux. The results show that wind erosion flux is maximal at the beginning of the rainy season while wind speeds are high. Dunes front without fixation device are more mobile. On their surfaces wind erosion happened all the year because of wind speed is regularly superior to the thres...

Piping is one of the main causes of the earth-fill dam failures. Most of the researchers realizing numerical analyses make some simplified assumptions concerning the shape of the breach and the discharge of water flowing through the breach. The aim of this study is to realize experiments to provide data needed to perform numerical analyses by making more realistic assumptions. The dam having a height of 0.6 m, a bottom width of 2 m and a crest width of 0.20 m is built in a channel 1 m wide, 0.81 m high and 6.14 m long. The evolution of the breach and the discharge through the breach resulting from piping due to seepage at the earth-fill dam bottom was investigated experimentally. The evolution of the dam failure is recorded by six cameras located at different locations. The time-varied of the breach areas at upstream and downstream sides are determined by applying the Gauss Area functions. The discharge of water through the breach and average outflow velocity are determined by using the continuity equation.

International Science Congress Association 14 Grain Sorting on a Coastal dune of Orissa, Bay of Bengal and a comparison with the Desert Dune of Rajasthan, India Barendra Purkait, Dipanjan Das Majumdar and Ashis Kumar Paul Department of Geology, University of Calcutta, 35 B. C. Road, Kolkata700 019 INDIA Department of Remote Sensing and GIS, Vidyasagar University, Midnapore, West-Bengal – 721102, INDIA Department of Geography and Environment Management, Vidyasagar University, Midnapore, West-Bengal – 721102, INDIA

Enigmatic structures grouped under the term "shark-fins" are documented in laminated deposits of pyroclastic currents. They consist of an overturning of a few laminae on a decimeter scale, forming overbent "flames" or convolute laminae, which occur in successive, periodic patterns. More than 200 shark-fins were investigated and measured in cross-laminated deposits from the 2006 pyroclastic currents of Tungurahua volcano (Ecuador). Shark-fins often underlie erosive lines. They occur in periodic repetitions or amalgamated in swarms and can show signs of migration as well as concurrent growth during sedimentation. These shark-fins are interpreted in terms of syn-depositional soft sediment deformation. The patterns are interpreted as due to the reworking of the bed by wave instabilities, which form around a shear horizon between a traction carpet and the bed. A theoretical framework based on two fluid layers separated by a shear horizon is adapted from the Holmboe instability problem. The calculated growth rates of the waves are compared to sedimentation rates in order to infer aspects of the stability and preservation of the sheared interfaces. The good agreement of the physical model with field data supports the process-based interpretation. In particular, such modified Holmboe instabilities seem more adequate than Kelvin-Helmholtz instabilities to explain overturned sharkfins structures. Other incidental overturned patterns are presented and discussed, which likely result from an intraflow event as well as from syn-flow slumping. Such observations on flow-bed interactions contribute to the understanding of a flow rheology, shear partitioning, and the transmission of shear stress out of the flow and into the substrate.

Sand dunes of the Quaternary age occupy large areas of Iran's semiarid and arid regions. In this study, some 33 sediment samples were collected from the crest, the lee and stoss sides of the linear dunes of the southern part of Qazvin plain. Sedimentological, geochemical, and mineralogical investigations were carried out in order to identify the origin and probable source of the aeolian dune sands. Grain size analysis of the sediments shows that most of the aeolian sands are generally fine-grained, moderately well-sorted, fine skewed and leptokurtic. The textural, mineralogical and the geochemical results supported by the statistical approach indicate that the dune sands were mainly derived from the Quaternary flood plain with a minor contribution from alluvial and fluvial sands. Facies study leads to the determination of 4 facies in 2 facies associations, including: 1) medium-grained lithofacies (Sdpc, Sdl, and Sdm), and 2) gypcrete facies (G). The studied aeolian sands are characterized by the predominance of gypsum and quartz, and stable minerals together with sedimentary, metamorphic, and volcanic fragments, and a few unstable pyroxene and amphibole minerals. The sand dunes of the Qazvin Plain record a semi-arid to arid paleoclimate and the relatively stable tectonic background characterized by the mineralogical and geochemical composition and gypcrete facies in the dunes.

Structure from Motion-Multi-View Stereo (SfM-MVS) is a relatively new technique that is being adopted in the analysis of sedimentary systems. The technique is especially applicable to studies which focus on the distribution, geometry and quantification of geological bodies including the analysis of sedimentary forms and tectonic structures. This photogrammetric method allows for generating virtual outcrops (VO) and high-resolution digital terrain models (DTMs). In comparison with more sophisticated and expensive techniques such as airborne LiDAR scanning or terrestrial laser scanning, SfM-MVS is a fast low-cost method which with careful use of ground control points, can produce models which are comparable to other digital survey methods for spatial accuracy. In this study, the effectiveness of SfM-MVS in a series of quantitative case studies in sedimentary and basin analyses is discussed. Focus is placed on how the research questions define the workflow strategy to know the limitations, sources of error and potential utility that the SFM-MVS technique has when a virtual sedimentary system is interpreted. Three case studies of different sedimentary environments, previously analyzed with traditional fieldwork techniques, were selected and re-analyzed. For each case study the objective was to resolve quantitative questions that were not possible to determine without the use of VO or DTMs. Questions include: (i) geometrical restoration of a growth strata succession associated with thrust systems; (ii) stacking patterns of littoral ridges during a relative sea-level fall after the Holocene climatic optimum; and (iii) quantification of lake level fall during the past 44 years of a closed lake basin. The results of the work show that the technique has significant application in the analysis of sedimentary systems. However, since geological interpretations depend on the quality of the models that are generated, planning and construction of the VO or DEMs along with their validation are essential to ensure reliable results.

Two large-scale sediment deformation structures, minor fold occurrences in cross-bedded sand dune deposits and complex convolute folds, are observed in red sandstones, in a zone about 1.5 km long in floodway cuts at the Sérgio Motta/Porto Primavera dam, São Paulo state, Brazil. The most important structures are confined to planar zones, up to 10 m thick, in undeformed dune foreset strata were they can be traced laterally for about 50-60 m. The sandstones are part of the Rio Paraná Formation, Caiuá Group, which accumulated in a great sand sea of about 100,000 km 2. The Caiuá Desert developed during the Late Cretaceous in the southern part of the Bauru Basin, an intracontinental subsiding area in the central-southern part of the South-American Platform. The basin was filled by a sandy sequence about 300 m thick. The sand sea deposits correspond to the Caiuá Group and comprise: a) deposits of dry sand sheets (Santo Anastácio Formation), b) deposits of medium-sized dunes and humid interdunes of the sand sea peripheral zones (Goio Erê Formation), and c) deposits of large-sized complex aeolian dunes and draas, that correspond to the central part of the inland sand sea (Rio Paraná Formation). The deformations in the sediments are attributed to the effects of fluidization, liquefaction and shear stress, which are interpreted as being earthquake-induced structures, mainly because: (1) the deformed horizons are confined between undeformed cross-bedded strata, (2) the complex convolute folds sometimes include nappe-like structures that overlie foreset facies, (3) during the Bauru Basin infilling there was tectonic activity associated with alkaline volcanism on the borders of the basin and related silicification in the central-southern part. The main silicification zones are aligned to regional lineaments that cross the area near the large-scale sedimentary deformation structures.

Patchy aeolian landforms, representing the NE part of the European Sand Belt, occur in NE Estonia, between the Gulf of Finland and Lake Peipsi. The dunes are restricted to the former glacial lakebed, thus lying directly in contact with glaciolacustrine sediments, and have so far prompted different opinions regarding their genesis and age. This study aims to answer these open questions regarding the age and origin of these landforms and to provide information on the associated past sedimentary processes. To achieve this, we combine macro-scale (sedimentary structures and ground-penetrating radar survey) and micro-scale (grain-size, shape and character of quartz grain surfaces and mineral composition) studies with optically stimulated luminescence dating. The glaciolacustrine fines in the study area are wavy stratified, with the occurrence of mica horizons and prevalence of quartz sand grains with aeolian characteristics. Therefore, these sediments argue for near-standing/low-energy water conditions in the glacial lake, where allochthonous material was delivered by wind. A fall in the lake level and the occurrence of dry land on the northern coast of the regressive Late Weichselian Lake Peipsi favoured aeolian activity from ca. 13.5 to 10.5 ka in the region. The aeolian accumulation was brief-as apparent from the results of the micro-scale study-and lacks evidence of sediment recycling. Only easily-removable mica was deflated at the end of the aeolian depositional phase. Aeolian activity terminated ca. 10.5 ka due to a rising groundwater level that is apparent from the onset of paludification in the region.

Blake, D. T. Vaniman, C. N. Achilles, N. Castle, S. J. Chipera, P. I. Craig, D. J. Des Marais, R. T. Downs, J. Farmer, R. Hazen, B. Horgan, M. Lapotre, D. W. Ming, R. V. Morris, S. M. Morrison, T. S. Peretyazhko, A. H. Treiman, V. Tu, A. S. Yen. NASA JSC (elizabeth.b.rampe@nasa.gov), NASA Ames, PSI, Univ. Ariz., LPI/USRA, CHK Energy, Ariz. State Univ., Carnegie, Purdue, Harvard, Jacobs at NASA JSC., JPL

Sedimentological, mineralogical, morphological and geochemical studies of sand dunes from ten locations in Saudi Arabia were conducted in order to determine the differences between them and to find out the provenance and tectonic setting of these sand dunes. Sixty seven samples were collected from different sand dunes types ranging in morphology from linear, barchans, parabolic to stars dunes. In overall, the sand dunes are fine to coarse grained mean grain size, moderately sorted, near symmetrical skewness with mesokurtic distribution characterized sand dunes in most locations. The sand dunes grains are subrounded in all locations except in the Red sea, Qassim, central Arabia and the eastern province which showed sub-angular grains. The main mineral compositions of studied aeolian sand dunes are quartz, feldspar, calcite, and mica. Quartz is the dominant mineral in locations with significant amount of feldspars and mica in Najran, Red sea and Central Arabia locations. Moreover, calcite is present in Sakaka and NW Empty Quarter (Jafurah). Basement related sand dunes in Najran, Central Arabia and Red sea locations are sub-mature in terms of their mineralogical maturity. Whereas, sand dunes in other locations are texturally mature except those from the Red sea which showed sub-mature sand. The sands are classified as quartz arenite, except in the basement related sand dunes in Najran, central Arabia and the Red sea are ranging from sub-arkose, sub-litharenite and lithraenite. Morphologically, parallel to sub-parallel sand ridges with NE-SW orientation occurred in east and north parts of Empty Quarter (Najran and Jafurah) and NW-SE orientation in Dahna and Nafud deserts in central and north regions of Saudi Arabia. Parabolic sand dunes characterized the Nafud desert (Hail, Sakaka, Tayma locations). Barchans and star sand dunes characterize the Empty Quarter (Jafurah). Major, trace, and rare earth elements studies were carried out to determine the composition, provenance and tectonic history of the sand dunes. Geochemical analysis indicated that most of sand dunes are quartz arenite type, except in the Red sea, basement related central Saudi Arabia and Najran areas, the sand dunes are sub-arkoses, sub-litharenite and litharenite. The concentration of major,trace and rare elements showed active continental margins as a tectonic setting of Red sea, basement related Najran and central Arabia sand dune. In contrast, passive continental margins for the other locations. The distribution of major, trace and rare earth elements showed similarity in chemical composition between basement related sand dunes in Red sea, Najran and central Arabia.

Modifications to valley form due to extreme flooding in the lower 34 km of the Ha! Ha! River were analyzed. Heavy regional precipitation in July 1996 triggered extreme runoff and the catastrophic drainage of Ha! Ha! Lake, producing discharges of 1100 m3/s, 8 times the 100‐year flood. Dominant valley modifications, revealed by comparing preflood and postflood topographies derived photogrammetrically, were related to two large‐scale avulsions; in particular, a deep retrogressive incision which bypassed the 30‐m‐high Perron Falls, exporting 6 × 106 m3 of glacial stratified drift from a 2‐km section of valley and producing massive sedimentation in the reach downstream. Reconstructed maximum flow power values support the existence of a 300 W/m2 threshold for major scouring of the alluvial valley bottom. The evidence highlights the potential for massive scour and fill and reorganization of the long profile, with potentially catastrophic effects on infrastructure, during extreme floods in ...

As dunas da região costeira do Estado do Ceará estão formadas por acumulações do tipo lençol de areia e barcana, cujas dimensões, relações geométricas e taxas de migração foram estudadas a partir de dois tipos de aproximação. Como principal resultado, se observa que as dunas barcanas apresentam uma relação geométrica de equilíbrio, caracterizada pelos parâmetros adimensionais H/W e W/L. As dunas são altamente móveis, com taxas média de migração de 17,5 m/ ano para as barcanas e 10 m/ano para os lençóis de areia. As taxas de migração calculadas para esses dois tipos de dunas apresentam uma relação inversa com suas. Esta relação está associada à existência de uma taxa de transporte comum ao longo dos campos de duna, que induz uma resposta geomorfológica diferenciada e dependente das dimensões das dunas. A partir da evolução multitemporal das dunas foi possível estimar a taxa de transporte eólico de sedimentos para a região, cuja magnitude é da ordem de 90-100 m 3 /m/ano. Ao final, destaca-se algumas implicações da migração das dunas para a área de estudo.

The study aims to determine mean annual wave heights and wind speeds in the Adriatic Sea. The Adriatic serves as a shipping route towards central Europe and a food and energy source for surrounding countries. Wave and wind climate information can serve as basis for design, research and policy making regarding ship safety and operability, potential renewable energy exploitation, design of offshore installation etc. Mean annual wave height and wind speed values have been statically derived based on 43,274 ship sea state observations reported by the Hydrographical Institute of Republic of Croatia. This data has been digitalized and processed resulting in mean annual observed wave heights and corresponding wind speed values. Calm sea and no wind time percent periods have been calculated and wind-speedto-wave-height correlations presented. The obtained results are discussed for accuracy, significant effects are listed and future work guidelines are given.

The beaches represent dynamic environments and exchange of energy and matter between the continent and the ocean. The transport of sediments is constant and the features are constituted by unconsolidated materials, being characterized by maintaining fragile structures for the processes of human occupation. From granulometric analyzes performed according to preestablished protocols, it was possible to define the granulometric and chemical composition of the sands of the Barriers Beach and Lighthouse, in the city of Camocim, west coast of the State of Ceará. In the beach zone, subdivided into backshore, foreshore and nearshore, there are lithoctic sands, litobioclastic sands and bioclastic rocks, containing high concentrations of calcium carbonate from organic agents (shells, corals, algae etc.) and inorganic (from the ocean or continents), as well as the erosion of beach rocks.

The scanning electron microscope photograph of the clay slide (fig. 1) prepared in this manner shows that the clay-size particles are welloriented. The preparation time for two (or multiple of two, depending on the capacity of the centrifuge) slides is less than one hour.

Piping is one of the main causes of the earth-fill dam failures. Most of the researchers realizing numerical analyses make some simplified assumptions concerning the shape of the breach and the discharge of water flowing through the breach. The aim of this study is to realize experiments to provide data needed to perform numerical analyses by making more realistic assumptions. The dam having a height of 0.6 m, a bottom width of 2 m and a crest width of 0.20 m is built in a channel 1 m wide, 0.81 m high and 6.14 m long. The evolution of the breach and the discharge through the breach resulting from piping due to seepage at the earth-fill dam bottom was investigated experimentally. The evolution of the dam failure is recorded by six cameras located at different locations. The time-varied of the breach areas at upstream and downstream sides are determined by applying the Gauss Area functions. The discharge of water through the breach and average outflow velocity are determined by using the continuity equation.

Sands and calcite cement-bodies (the Baran6w Beds) from Swiniary, eastern margin of the Holy Cross Mts. The paper presents the results of studies of sands with horizons of sandstones in the fonn of calcite cement-bodies from §winiary near Baran6w Sandomierski. Besides a IIUlCros~opic description numerous laboratory tests such as SEM viewing, X~ray diffraction and trace elements content have been applied in these gediments. Motfology and microtexture of quartz grains enable detennination of differences in the sedimentation environment of each part of the discussed sand deposits: from a marine basin with distinct innuence of a shore :rone, through a gradual change of pbysical-chemical conditions connected with deepening. followed by a decrease of shore zone grain content and increase of chemical features content. Chemical analyses of the cement and character of quartz grain surfaces from the calcite cement-bodies point to a complicated course of diagenetic processes connected with precipitation of calcite and barite and synchronous quartz dissolution and silica dmining. The trace elements content of the cement points to non-marine source of cements. The age of diagenetic processes may be defined as Pliocene till present.

The aim of the present study is to determine the location and morphometric characteristics of fluvial islands in a 234.5 km long reach of the River Neris (from the Lithuanian-Belarusian border till the mouth of the river), to evaluate the changes of their number, area and location that have occurred since the second half of the 20th century, and to analyse the main geological and hydrological factors which possibly have affected the development of these islands. The fluvial islands, i.e. river channel forms situated above the average long-term water level, separated from the land by river branches and generated by fluvial processes, i.e. by the interaction of ground and surface water flows or, in other words, by erosion-accumulation processes taking place in the river basin, are fully or partly covered by vegetation and best reflect the external scenery of the river. Islands are scattered over the whole investigated reach of the river, yet their number highly depends on morphometric, hydrogeological and geological conditions in different segments. Small islands are dominant (area b1 ha, height up to 1 m). They account up to 89% of the total number of islands, yet their total area accounts only up to 33% of the total island area in the studied segment. The minimum number of islands (1 island in a 10 km long segment on the average) is observed in the segments where the river flows across morainic massifs and in the relatively straight segments. The maximum number of islands (1 island in a 1 km long segment) occurs downstream from the eroded segments where they occupy up to 5.4% of the river channel area. During the last 40 years, both the number and the area of fluvial islands have increased. The increasing area of the fluvial islands in the channel reduces transportability of the river flow. Investigations of the flow showed that at the end of the 20ththe beginning of the 21st century the annual peak discharge was 48% smaller than comparing to the end of the 19th start of the 20th century. Due to the reduction of the flood plain area and shorter duration of floods, the amount of sediments left in the flood plain has been continuously decreasing. This might have been caused by the increased sedimentation in the channel resulting in the intensive formation and accretion of the islands. In the future, the reduced transportability caused by the increasing number and area of the fluvial islands may predetermine higher and longer floods and higher flood hazards for the urbanised riverside territories under the conditions of the same discharge.

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The eolianites, distributed along the northwestern part of Ceará State coast, are formed by arenaceous rock deposits of quartz-bioclastic composition, cemented by calcium carbonate. This unit establishes an unique record of aeolian activity with peculiar features, rare on the ...

Considering the evolution of aeolian to marine transitions for the geological record, either catastrophic or gradual transgressive scenarios showing high or low rates of coastal migration have been proposed. A critical evaluation of modern analogues suggests that a catastrophic transgression shares many characteristics with Holocene transgressions, yet they are caused by different rates of sea‐level rise. The present study provides insights into the evolution of aeolian to marine transitions in order to discuss these alternative scenarios of sea‐level rise. For this purpose, a sedimentological and ichnological analysis was carried out on ten stratigraphic sections of the Picún Leufú area, Argentina. There, marine deposits of the Vaca Muerta Formation accumulated over the aeolian deposits of the Quebrada del Sapo Formation during the early Tithonian. The sedimentary evolution of the transition can be summarized in: (i) a shutdown of aeolian dune field deposition, generating a plana...

Considering the evolution of aeolian to marine transitions for the geological record, either catastrophic or gradual transgressive scenarios showing high or low rates of coastal migration have been proposed. A critical evaluation of modern analogues suggests that a catastrophic transgression shares many characteristics with Holocene transgressions, yet they are caused by different rates of sea‐level rise. The present study provides insights into the evolution of aeolian to marine transitions in order to discuss these alternative scenarios of sea‐level rise. For this purpose, a sedimentological and ichnological analysis was carried out on ten stratigraphic sections of the Picún Leufú area, Argentina. There, marine deposits of the Vaca Muerta Formation accumulated over the aeolian deposits of the Quebrada del Sapo Formation during the early Tithonian. The sedimentary evolution of the transition can be summarized in: (i) a shutdown of aeolian dune field deposition, generating a plana...

Considering the evolution of aeolian to marine transitions for the geological record, either catastrophic or gradual transgressive scenarios showing high or low rates of coastal migration have been proposed. A critical evaluation of modern analogues suggests that a catastrophic transgression shares many characteristics with Holocene transgressions, yet they are caused by different rates of sea‐level rise. The present study provides insights into the evolution of aeolian to marine transitions in order to discuss these alternative scenarios of sea‐level rise. For this purpose, a sedimentological and ichnological analysis was carried out on ten stratigraphic sections of the Picún Leufú area, Argentina. There, marine deposits of the Vaca Muerta Formation accumulated over the aeolian deposits of the Quebrada del Sapo Formation during the early Tithonian. The sedimentary evolution of the transition can be summarized in: (i) a shutdown of aeolian dune field deposition, generating a plana...

The studies were conducted in a dry valley in NE Poland. They were aimed at determining the origin of this structure and tracing the processes that have shaped the dry valley in a time span of about 130 ka. The research included detailed geological mapping, including piercing of a number of boreholes and electrical resistivity tomography (ERT) surveys. The obtained material was pollen analysed, OSL dated, and the grain size distribution and the morphoscopy of sand quartz grains were investigated; additionally the organic matter (OM) content was determined. Based on the obtained results it was concluded that the structure currently occupied by sediments of the dry valley was formed during the Warta Stadial of the Odranian Glaciation (Saalian; MIS 6) as a glacial tunnel valley. Small, probably isolated depressions functioned in the dry valley bottom after the ice sheet retreat. The sediments record a full succession of climate oscillations from the Eemian Interglacial (MIS 5e) (pollen zones E1 to E7) through the Early Vistulian (MIS 5a-5d) to MIS 4. In the Early Vistulian, the depressions functioned as lakes, or got shallower and were replaced by peat-bogs, depending on the climate conditions. During MIS 4, the bottom of the dry valley was subjected to erosion as a result of concentrated water flow. This caused draining of the existing depressions and their incorporation within the flow. Probably during MIS 3, solifluction was activated on the slopes of the dry valley. During LGM, permafrost aggradation occurred in the study area, recorded by two generations of epigenetic sand wedges and development of aeolian processes. In contrast to analogous processes within the European Sand Belt, the latter processes acted for a short time and only locally. The final record are Holocene soils. It seems that the analysed valley is a good example of palaeoenvironmental conditions in Eastern Europe.

Pyroclastic density currents represent one of the most destructive hazards associated with explosive volcanism. This destructive nature does not only urge the need for but also prevents the obtainment of in situ measurements of their physical characteristics. The resulting deposits offer, however, evidence of the physics of their sedimentation phase. Deposits of dilute pyroclastic density currents frequently exhibit repeated cycles of deposition and erosion, yielding insights into the turbulent shearing along the ground. The utilization of such field observations can be greatly enhanced by the calibration of physical properties of such flows under well-constrained laboratory conditions. Here, wind tunnel measurements were performed using pyroclastic particles. The saltation threshold and surface roughness length were calculated for wind above a pyroclastic bed. The results serve as an aid in linking field observations to quantitative values of turbulent shear at the base of a flow. Scoria and pumice particles were investigated as a function of grain size (1 ϕ fractions between 0.125 and 4 mm), as well as the influence of bedslope (−20°to +25°in 10°steps). The results point to the dominant control of density, grain size and, contrary to previous assumptions, differ moderately from results obtained for round beads. Properly utilized, the dataset enables the establishment of a link between the grain size of natural deposits and the shearing extant during their emplacement. Depending on the type of sedimentary structure observed in the field, the saltation threshold can be used as a minimal or a maximal shearing limit during emplacement of dilute pyroclastic density current deposits. Stoss-aggrading laminations likely involve the saltation threshold as an upper limit, whereas for truncation events it must have been overcome. The effect of particle concentration within the flow, a critical parameter for pyroclastic density currents and the extent of validity of the data, are discussed.