Sedimentology and modelling of the Mitterndorf Basin

Die Mitterndorfer Senke ist das größte Pleistozän Becken in Österreich. Das Becken hat sich entlang der sinistralen Wiener Becken Transfer Störung ausgebildet. Im Bereich dieser wichtigen Blattverschiebung haben sich durch fortlaufende Bewegung Stoerungsflächen gekrümmt (befreiende Kruemmung oder auch releasing bend) und Platz für die Beckenformation geschaffen. Die bis zu 170 m mächtigen quartären Sedimente spiegeln die deutlichen Klimaveränderungen während des Quartärs in ihrer Lithofacies wider. Die massiven, grobkörnigen Sedimente stellen ein sehr großes Porenvolumen und damit auch ein bedeutendes Aquifer dar. Es ist eines der größten Europas. Die Kenntnis der Beckenstratigraphie ist damit nicht nur entscheidend um dieses Aquifer besser zu verstehen, sondern auch um die in der Lithofazies vorhandene Information zur Klimatik und Umwelt besser zu verstehen. Intensive Feld- und Laborarbeit wurde durch computerisierte Datenprozessierung unterstützt. Die gesamten Daten, betreffend Geologie (z.B. Bohrlogs, Feld- und Labordaten), Geophysik (z.B. Bouguer Schwere, Geoelektrikdaten, Seismikdaten) und Geographie (Luftbilder, Topographische Information) wurden in ein Geographisches Informationssystem integriert. Diese große Datenbank stellt die Plattform für alle statischen und gerichteten Modelle dar. Drei wissenschaftliche Arbeiten wurden bisher geschrieben und eingereicht: Salcher and Wagreich (2008) haben den Einfluss von Klima und Tektonik auf die Lithofazies des Mitterndorfer Beckens untersucht. Die grobkörnige, massive Fazies steht im Zusammenhang mit hochenergetischen Flutereignissen die ein ausgeprägtes nivales Regime während der Glaziale anzeigt. Im Gegensatz dazu stehen feinkörnige, gut geschichtete Sedimente die Perioden eines großen Verhältnisses von Niederschlag zu Sedimenttransport zeigen. Günstige Sequenzenpreservationseigenschaften wurden durch Subsidenzraten von etwa 0.5 bis 1 mm pro Jahr geschaffen. Die Subsidenzraten sind in der Regel auch groß genug um einen großen Teil warmzeitlicher Information vor Erosion zu bewahren. Dieser Teil fehlt in fluviatilen Terrassen häufig. Neue 14C und relative Alter die aus dem Studiengebiet entstammen beweisen den starken Einfluss klimatischer Oszillationen auf das Klima und auf die fluviale Stratigraphie im Zeitraum von MIS3 bis MIS1. Salcher, Meurers, Decker, Wagreich (2008) haben eine Technik verwendet um Bouguer Schweredaten auf ihre hochfrequenten Anteile zu filtern und oberflächennahe Strukturen zu beleuchten. Verschiedene erste Ableitungen wurden verwendet um eine genaue Störungslokation zu erhalten. Zusammen mit Loginformationen aus Bohrungen wurde ein neues und genaues Modell des Mitterndorfer Beckenuntergrundes erstellt. Das Modell zeigt den kinematischen Einfluss auf die Beckengeometrie und auf Störungsaktivität während des Pleistozäns. Reichhaltige Information wie 2D, 3D Seismik, Geoelektrik-, Log- und Erdbebenaktivitätsdaten wurden verwendet um die die Übereinstimmung der Strukturen mit den Schwereanomalien zu demonstrieren. Zusätzlich wurden Computermodelle gerechnet um die Effektivität der Ableitungen zu beweisen und auch um Dargestelltes besser zu interpretieren. Resultate zeigen nicht nur den Einfluss von Störungen auf die Landschaftsentwicklung. Es konnte gezeigt werden dass diverse geomorphologische Strukturen tektonisch bedingt sind wie Z.B. Böschungen, Gräben und Täler. Salcher, Faber, Wagreich (2008) haben klimatisch bedingte Aggrations- und Degrationszyklen, den Einfluss von Subsidenz und Änderungen des fluviatilen Akkomodationslevels mittels eines numerischen Models untersucht. Der Modellierungszeitraum betrug 25.000 Jahre. Die Modelle, so genannte Landschaftsevolutionsmodelle, beschreiben Langzeitänderungen von Oberflächenformen. Die Modelle haben von den reichlich vorhandenen Daten profitiert und wurden an den naturalistischen Bedingungen des Untersuchungsgebietes kalibriert. Diesbezüglich wurde der Programmkode erweitert und implementiert. Die resultierenden Modelle zeigten dass Änderungen der Sedimentzufuhr die stärksten Auswirkungen auf das System haben. Starke Änderungen der Sedimentzufuhr hängen direkt mit den klimatischen Bedingungen im Einzugsgebiet zusammen. Der Einfluss von Subsidenz ist geringer und wird erst nach einer längeren Zeit deutlich. Änderungen des Akkomodationslevels wirken sich prinzipiell stärker und schneller aus, haben aber für die Mitterndorfer Senke keine Bedeutung. Beide können sich während längeren, klimatisch wärmeren Perioden besonders deutlich auswirken.The Mitterndorf Basin is the largest Pleistocene Basin in Austria. The basin is linked to a releasing bend along the major Vienna Basin transfer fault. Basin formation is supposed to start during the Middle Pleistocene. The up to 170 m of accumulated Quaternary sediments show strong variations in their lithofacies reflecting distinct climate oscillations. Massive coarse grained sediments provide huge pore space making the Mitterndorf Basin to one of Europe s largest drinking water reservoirs. Knowledge about the basin's stratigraphy is therefore not only crucial to better understand this important aquifer, basin's subsidence and associated preservation of lithofacies provide also valuable information on Quaternary climate and environment. Intense field and lab work was supported by computer data processing. All data concerning geology (e.g. drill logs, field and lab data), geophysics (e.g. Bouguer gravity, geoelectric data, seismic data) and geography (e.g. aerial images, topographic information) were integrated in a geographic information system (GIS). This major database builds the platform for all static and forward models. Within the 3 years of this PhD, 3 scientific papers have been written so far: Salcher and Wagreich (2008) investigated the impact of climate and tectonic on the lithofacies in the Mitterndorf Basin. The coarse grained, massive facies is associated with high-energetic flood events reflecting a distinct nival regime during glacial times. In contrast, fine grained, well stratified sediments mark periods of rather high discharge to sediment supply ratios during warmer periods. Sequence preservation was provided by subsidence rates of approx. 0.5 to 1 mm per year. High subsidence rates preserve a relatively large record of sequences compared to fluvial terraces which reflect mainly sediments deposited during and shortly after glacials. New 14C and relative ages demonstrate the strong impact of oscillations in climate on fluvial stratigraphy covering times from the upper period of MIS 3 to the MIS 1. Salcher, Meurers, Decker, Wagreich (2008) applied a technique in Bouguer gravity filtering to high pass near surface structures. Different first order derivates of gravity data were used to precisely determine fault locations. Together with drill log information a new and considerably more accurate model of the Mitterndorf Basin's underground was developed. The presented model demonstrated the kinematic (sinistral, pull apart basin) impact on the basin geometry and on fault activity during the Pleistocene. Abundant geophysical and geological data such as 2 D, 3 D seismic, geoelectric, log and outcrop data were used to verify coincidence of structural features with gravity anomalies gained from derivatives. Additionally, numerical models were carried out to better understand effectiveness of derivatives and better interpret gravity anomaly features. Results do not only demonstrate the impact of faults on landscape development. It could be demonstrated that diverse geomorphologic features have a tectonic origin such as scarps, grabens and valleys. Salcher, Meurers, Decker, Wagreich (2008) have been among the first to apply gravity high pass filtering technique in general and the first who demonstrate the suitability in a continental Pleistocene Basin. Salcher, Faber, Wagreich (2008) used a numerical model approach to investigate climate induced aggradation and degradation cycles, the influence of subsidence and the impact of base-level change (Danube) on this large Pleistocene basin within a time frame of 25 ka. Models were carried out as landscape evolution models describing long term changes in size, shape and relief of landforms. Models were calibrated on real world conditions benefiting from abundant data of the study area. New codes were tested and implemented. Software (SedTec) provided excellent calibration possibilities, helping to make models more realistic. Our models showed that adjustments in sediment supply mainly impact basin's sequence evolution. Strong alterations in sediment supply are related to changing climate, ranging from cool or cold to warm and rather wet conditions. The effect of subsidence is minor compared to climate and only gets relevant over longer time spans. The impact of the axial main river (Danube) is principally strong and fast but has no relevance for the study area. Both factors are especially relevant during long lasting warm periods

The impact of the Bohemian Spur on the cooling and exhumation pattern of the Eastern Alpine wedge

Fold and thrust belt dynamics and architecture may largely be impacted by the geometry of the overridden basement. The Bohemian Spur, the subcrop extension of the Bohemian massif, guided thrust propagation leading to the arcuate shape of the orogen and a narrowing of the Molasse Basin at the transition to the between the W-E trending Eastern Alps and the SW-NE trending Western Carpathians. Thermochronological studies in the Eastern Alps were mainly focused on the core of the collisional orogen, where deformation has been most prominent. Further to the east, some FT work is concentrated along fault zones but thermochronometers with lower closure temperatures have hardly been applied to higher elements of the nappe pile. Due to the scarcity of the dataset and preferential application of fission track dating uppermost crustal cooling below ca. 80 °C remains undetected. In this study we present new apatite (U-Th)/He and apatite fission track data from clastic units of the Rhenodanubian Flysch zone and the Northern Calcareous Alps. We find reset ages, that monitor a so far un(der)appreciated phase of prominent Late Oligocene to Miocene cooling. Thermal modeling of age data from the flysch samples reveals rapid Early Miocene cooling at rates of up to 40 °C/Ma between ca. 20 and 15 Ma. We propose a buttressing effect of the underlying tectonically structured eastern rim of the Bohemian Spur to be the driving mechanism for this phase of intensified exhumation. Our tectonic model (Fig. 1a) invokes contractional reactivation of pre-existing normal faults inherited from Penninic continental rifting. This positive inversion led to the shortening of the Jurassic half-graben infill and its extrusion as a major fold. Thermochronological data and thermal modeling of data from samples in the Lunz nappe of the Northern Calcareous Alps nappe pile indicate less punctuated cooling and exhumation. Modeling defines an increase of cooling rates at the latest at ca. 27 to 25 Ma, i.e., earlier than in the Flysch samples. Cooling occurred at a much lower rate of 3 to 6 °C/Ma and was synchronous with northward movement of the deformation front. In our tectonic model (Fig. 1b), we propose a staircase pattern that influences wedge dynamics: The topographically segmented downgoing plate leads to less localized and more distributed deformation invoking a broader area of uplift than the spatially focused uplift of the Flysch samples. Wedge propagation is initially inhibited or retarded by the relief of the basement. The ongoing northward movement of the propagating wedge is compensated through deep duplexing of the autochthonous foreland sequence. When calling upon deep-seated processes to explain the exhumation pattern the buttressing effect needs to be taken into account. Early Miocene drainage pattern reorganization in the Molasse Basin is proposed to be a consequence of uplift induced by the subcrop promontory

The Chironico landslide (Valle Leventina, southern Swiss Alps): age and evolution

In this study, we focus on the postglacial Chironico landslide in Valle Leventina, the valley of the Ticino river immediately south of the Gotthard pass (southern Swiss Alps). At Chironico, 530 millionm3 of granite gneiss detached from the eastern wall of Valle Leventina and slid along valley-ward dipping foliation joints and fractures. The slide mass was deposited into the valley bottom and blocked the Ticino river, as well as a tributary, the Ticinetto stream, on the opposite side of the valley. Wood fragments found in lacustrine sediments in the slide-dammed upstream lake were previously dated, yielding a minimum age for the landslide of approximately 13,500calyears BP. Based on the deposit morphology, the landslide was in the past interpreted as being composed of two events. In order to directly date the landslide, ten boulders were dated using the cosmogenic nuclides 10Be and 36Cl. Mean exposure ages indicate that the landslide occurred at 13.38±1.03ka BP, during the Bølling-Allerød interstadial. This implies that the Chironico landslide, one of the few pre-Holocene slides known in Alps, is also the oldest in crystalline rock. With runout modelling using DAN3D we could reproduce the hypothesized single-event failure scenario, as well as the character and extent of motion of the landslide mass. Both the ages and the modelling suggest that the landslide was released in one event around 3,000years following deglaciation

Glow up: does a professional photoshoot intervention affect self-esteem and emotions among adolescent psychiatric patients?—A longitudinal intervention study

BackgroundToday, online communication is shaped by a billion-dollar social media (SM) and social networking site (SNS) industry. Visual content consumed by children and adolescents has been shown to influence behavioral patterns, state emotions, and self-esteem (SE). In this study, we introduced a novel intervention creating visual content through a professional photoshoot and investigated its impact on state emotions and SE in child and adolescent psychiatric (CAP) patients.MethodsStandardized and validated self-rating questionnaires were used to assess SE, state emotions, coping mechanisms, psychopathological symptoms, and internet use behavior at baseline. SE and state emotions were monitored at different time points around a professional photoshoot within 45 CAP patients (30 female patients; mean age, 15.1 years) using a longitudinal design.ResultsWithin-subject repeated-measures ANOVA and bootstrapped paired-sample t-tests showed a significant fluctuation in state emotions and SE throughout the intervention. Spearman correlations and univariate logistic regressions revealed that internalizing symptomatology and maladaptive coping significantly worsened the outcome of the intervention on state emotions and SE in girls. Internet-related variables heightened the positive effect of the intervention in boys and lowered SE in girls during the intervention.ConclusionThe photo intervention had various gender-specific effects. Boys did benefit from the intervention in terms of longitudinal outcome on positive state emotions (PE) and SE, even positively influenced by SNS and SM. Thus, it might be concluded that online social comparison was processed more beneficial in boys. In contrast, when working with visual content in girls, psychopathology and coping must be considered. Internet consumption in general, especially SM and SNS, was related to low SE in girls. Nevertheless, when therapeutically accompanied, the “glow up moment” during the shoot (high on PE and SE; low on negative state emotions) could be used as an index moment for therapeutic reflection

Geografiska Annaler: Series A, Physical Geography / Geophysical, topographic and stratigraphic analyses of perialpine kettles and implications for postglacial mire formation

Kettle holes are common ice decay features in formerly glaciated areas. They are highly variable in size and geometry and may form in a variety of glacial and glaciofluvial landforms. Kettle holes are either dry or exist as wetlands or lakes, only rarely transforming into kettle-hole mires. This study investigates Late Pleistocene kettles in the area of the LGM Salzach Glacier Lobe in the North Alpine Foreland. Kettles are here specifically well preserved and concentrate along the former glacier lobe terminus, where they could develop within large elevated areas protected from pro and postglacial sediment redistribution also showing minor anthropogenic overprint. Highest kettle concentrations were observed within a narrow swath along the distal lobe dominated by terminal moraines, ice wastage and outwash deposits, whereas they are almost absent in the centre of the former glacier lobe. Based on a new dataset on regional kettle distribution and a study of comparable wetland environments, we show that kettle lake formation is a specific but rare phenomenon, which is closely related to the preceding dynamics at the glacier lobe and the glacial depositional environment. By applying geophysical surveys (electrical resistivity tomography, ground-penetrating radar), topographic as well as stratigraphic investigations (DEM analysis, core-drilling and radiocarbon dating), we explore the postglacial evolution of the Jackenmoos kettle and propose a modified model of peat formation in kettle-hole mires, mainly as a function of the centripetal growth of a floating mat covering a central subsurface water body.(VLID)249699

The degree of glacial modification controls non-glacial erosion in alpine landscapes

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Reconstructing basal ice flow patterns of the Last Glacial Maximum Rhine glacier (northern Alpine foreland) based on streamlined subglacial landforms

Based on high-resolution (sub)glacial geomorphological mapping, we present a first digital inventory of streamlined bedforms within the footprint of a Last Glacial Maximum (LGM) Alpine piedmont glacier. A total of 2460 drumlins were mapped across the Rhine glacier foreland. Glacial lineations and one field of subglacial ribs (ribbed/Rogen moraines) - the first record of this type of subglacial landform on the Alpine foreland-were identified. Two flowsets, associated with (i) the Rhine glacier's LGM maximum advance (Schaffhausen stadial) and (ii) a late LGM readvance (Stein am Rhein stadial), are differentiated. The vast majority of streamlined bedforms occur in fields aligned in a 16- to 30-km-wide swath upstream of the Stein am Rhein frontal moraines. Orientation and elongation of drumlins and glacial lineations set the basis for the reconstruction of paleo-ice flow. Basal flow paths of the LGM maximum advance are visually interpreted and restricted to the zone proximal to the former ice front. The flow field reconstructed for the late LGM glacier readvance (Stein am Rhein stadial) extends tens of kilometres upstream and is modelled implementing a recently published kriging routine. The derived basal flow patterns paired with information on ice surface levels from lateral and frontal moraines and combined with relative ice velocity differences inferred from spatial changes in bedform elongation reveal detailed insights on ice flow geometries, particularly during the glacier readvance. Reconstructed flowlines highlight basal flow under shallow ice that is strongly controlled by local topography evidenced by diverging around basal bumps and converging in (narrow) valley sections and troughs, where basal flow velocities, steered by topography, are high. Gained paleo-ice basal flow patterns offer new insights on landscape evolution of the northern Alpine foreland and provide evidence-based flow data to validate future physical modelling results.ISSN:0197-9337ISSN:1096-983

The Chironico landslide (Valle Leventina, southern Swiss Alps): age and evolution

In this study, we focus on the postglacial Chironico landslide in Valle Leventina, the valley of the Ticino river immediately south of the Gotthard pass (southern Swiss Alps). At Chironico, 530 million m3 of granite gneiss detached from the eastern wall of Valle Leventina and slid along valley-ward dipping foliation joints and fractures. The slide mass was deposited into the valley bottom and blocked the Ticino river, as well as a tributary, the Ticinetto stream, on the opposite side of the valley. Wood fragments found in lacustrine sediments in the slide-dammed upstream lake were previously dated, yielding a minimum age for the landslide of approximately 13,500 cal years BP. Based on the deposit morphology, the landslide was in the past interpreted as being composed of two events. In order to directly date the landslide, ten boulders were dated using the cosmogenic nuclides 10Be and 36Cl. Mean exposure ages indicate that the landslide occurred at 13.38 ± 1.03 ka BP, during the Bølling-Allerød interstadial. This implies that the Chironico landslide, one of the few pre-Holocene slides known in Alps, is also the oldest in crystalline rock. With runout modelling using DAN3D we could reproduce the hypothesized single-event failure scenario, as well as the character and extent of motion of the landslide mass. Both the ages and the modelling suggest that the landslide was released in one event around 3,000 years following deglaciation.ISSN:1661-8734ISSN:1661-872

Late-Pleistocene catchment-wide denudation patterns across the European Alps

We compile detrital 10Be concentrations of Alpine rivers, representing the denudation rates pattern for 375 catchments across the entire European Alps. Using a homogeneized framework, we employ state-of-the-art techniques for inverting in-situ 10Be concentrations into denudation rates. From our compilation, we find that (i) while lithologic properties and precipitation/runoff do influence erosion mechanisms and rates at the scale of individual catchments and in some specific Alpine regions, such controls do not directly stand for the entire Alps, (ii) as also previously suggested, catchment-wide denudation rates across the entire European Alps closely follow first-order Alpine topographic metrics at the scale of individual catchments or selected Alpine sub-regions. However, in addition to previous local-scale studies conducted in the European Alps, our large-scale compilation highlights a functional relationship between catchment-wide denudation and mean catchment slope angle. Catchment-wide denudation positively correlates with mean catchment slope up to a threshold angle (25–30°). Above this threshold, any correlation between catchment-wide denudation and slope as well as other catchment metrics breaks apart. We can reconcile these systematic patterns by proposing a regional erosion model based on diffusive-transport laws for catchments located below the slope threshold angle. In oversteepened catchments situated above-threshold slopes, erosion is stochastic in nature, as glacial carving likely caused a partial decoupling between hillslope and fluvial domains with complex topographic relationships and sediment connectivity patterns. Finally, we identify a first-order positive relationship between modern geodetic rock uplift and catchment-wide denudation for the European Alps. The observed spatial pattern is highly variable and possibly reflects the surface response to deep geodynamic mechanisms prevailing in the different Alpine regions. We conclude that today's topography and geomorphic features of the entire Alps are the result of a millenial-scale geomorphic response to past glacial processes and active rock uplift, highlighting a link between external and internal drivers for mountain erosion.ISSN:0012-8252ISSN:1872-682

Quantification of the damming and sediment trapping capacity of landslides and their dammed lakes: the example of the Hintersee landslide dam

International audiencePerennial landslide dams interrupt the sediment connectivity of rivers. Although most landslide dams do not persist for more than a few days, those that do can exhibit significant sediment trapping capacity. While water can pass through or over the dam, the sediment load is trapped upstream of the dam until the dam breaks or gradually erodes, or is completely filled with deposits. The volume of sediment stored in this way can reach up to three times the volume of impounded water, as we find by back-analyzing the lake Hintersee in southeastern Germany. In this work, we reconstruct the pre-landslide topography using Petrel and then use the Gerris shallow-water flow solver with a Voellmy rheology to back-analyze this landslide-dammed lake in the Bavarian Alps. We test several landslide release scenarios and different landslide rheologies to obtain the best-fitting reconstruction of the dam topography. We then fill the landslide dam with water and sediment using simple slope algorithms and validate the results against the current topography. Finally, we compare the landslide deposit thicknesses, water depths, and trapped sediment thicknesses of our different scenarios in order to provide new insight into the damming and sediment trapping capacity of landslides