Flysch Zone Research Articles

Lower Campanian calcareous nannofossils: Morphometry and palaeoenvironmental implications of the Aspidolithus group (Rhenodanubian Flysch Zone, Austria)

Our calcareous nannofossil study focused on eleven samples from the lower Campanian (UC14a–UC14b) of the Loibichl section, located in the Rhenodanubian Flysch Zone of the Austrian Alps. Relative counts of calcareous nannofossil assemblages were followed by a morphometrical analysis on 1021 specimens belonging to the Aspidolithus genus (Aspidolithus enormis and Aspidolithus parcus). For this analysis, a light microscope was utilized to improve our understanding of the taxonomic concepts of this group during a phase of rapid morphological evolution. The analysis included the maximum length (L), the width of the outer rim versus the small diameter of the central area (b/a), and the number of perforations in the central area. The CaCO3 content and bulk carbonate stable isotope ratios of δ13C and δ18O were analysed to facilitate stratigraphic and palaeoecological interpretations. Additionally, this study was to determine whether variations in nannofossil morphometrics were driven by changing palaeoenvironmental conditions. This study identified five morphotypes: A. enormis subsp. 1, A. enormis subsp. 2, A. parcus expansus, A. parcus parcus, and A. parcus constrictus. The morphometric analysis substantiated the differentiation between “small” morphotypes (L < 8.5 μm; A. enormis) and the “large” A. parcus group (L > 8.5 μm). However, the results did not show any significant patterns that would justify a natural separation of the “subspecies” within the A. enormis and A. parcus group. Our statistical analysis suggests that these morphometric changes may be related to various palaeoenvironmental proxies. Further high-resolution morphometric analysis is required to verify the impact of contrasting environmental factors on Aspidolithus-size variation.

Hydraulic parameters of Submenilite Formation of Ždánice Unit

This study aims to re-asses hydrodynamic tests of the Submenilite Unit of the Outer Carpathian Flysch Zone sediments, exposed at Přítlucká hora located near Rakvice village in South Moravian region, Czech Republic. We focused on four shallow, 6.0–7.6 m deep hydrogeological wells, drilled by Aqua Enviro s. r. o. company in 2005. The purpose of the drilling was a feasibility study for drainage of western part of Rakvice village. The sediments of the Submenilite Formation of the Ždánice unit that were drilled are dominated by compressed clays, claystones and siltstones, containing thin layers of sand and weathered sandstones. For the purpose of determining hydraulic parameters of underlying aquifer, the company conducted pumping and recovery tests on each of the wells. In this work, we used Jacob’s semilogarithmic method to interpret the measured groundwater level data. Hydraulic conductivity and transmissivity parameters were consequently calculated. The resulting transmissivity values range from 1.6 × 10–2 m2/d to 3.7 × 10–1 m2 /d and hydraulic conductivity value ranges from 3.6 × 10–3 m/d to 1.0 × 10–1 m/d. The calculated index of transmissivity Y corresponds to 4.32–4.57 and index of conductivity Z ranges between 5.80 and 6.27. The values of index of transmissivity Y from this study are generally comparable with results presented by previous authors and demonstrate very low transmissivity of the rocks of this unit mostly built by non-permeable pelitic rocks.

Internal structure of an active landslide based on ERT and DP data: New insights from the Hofermühle landslide observatory in Lower Austria

Slopes with clay-rich, deeply weathered soils, such as those present in the Flysch Zone of Lower Austria, are prone to landslide processes. Even though generally being of low magnitude and velocity, they can cause substantial economic losses and threaten settlements as well as infrastructure. Previous studies have demonstrated the importance of sub-surface information to further increase our understanding on landslide processes and triggers in different areas as well as to support any decision makers to determine any appropriate landslide mitigation measures. The combination of direct and indirect methods thereby has proven to be an adequate methodology, yet case studies are still needed to develop a universal strategy for the investigation of clay-rich landslides. In this study, we applied Electrical Resistivity Tomography (ERT) and Dynamic Probing Medium (DPM) to further investigate the complex Hofermühle landslide in the Flysch Zone of Lower Austria in order to improve our knowledge on sub-surface conditions. The focus is on the initially activated main landslide area, which has already formed earth-flow-like processes in the past. The methodology facilitated a representative characterization of the sub-surface. We were able to approximate the geometry and depth of slip surfaces, as well as the transition to bedrock, allowing us to delimit those parts of the slope which are likely to fail and, respectively be re-activated in the future. The results show that a range of thicknesses can be found in the investigated part of the Hofermühle landslide. In particular, near the surface, which has been altered by creep displacement and also by anthropogenic alteration, the resistivity is more variable compared to deeper, presumably less disturbed, layers. Furthermore, it is assumed that clay particles are transported with the surface runoff and deposited in the surroundings of the drainage channels, resulting in lower resistivity values and higher saturation at this locations. The location of the slip surface is interpreted to be on the surface of the bedrock, where there is a highly disturbed, clay-rich mass with no interbedded layers. Layers with lower resistivity directly above the bedrock indicate weathered material and remolding of materials during creep.

A comparison of the hydrodynamic characteristics of surface runoff generated by flash floods in geologically different areas of the Bohemian Massif (crystalline rocks) and the western Carpathians (flysch)

Abstract The geological environment is undoubtedly one of the basic factors that influence the formation of surface runoff. The extent to which this factor can also affect the hydrodynamic characteristics of flash floods, which is also indirectly associated with flood risk, is the main topic of this study. In two geologically different areas of the Bohemian Massif (crystalline rocks predominate) and the western Carpathians (flysch rocks predominate), a total of 40 watersheds characterised by sharing a certain hydrological analogy were selected (20 watersheds from the Massif and 20 from the Flysch zone). In each of these watersheds, 1-year, 10-year and 100-year flash flood return periods were constructed using the two-dimensional hydrodynamic model Iber. The outputs from this model included raster datasets of areas, depths, and flow velocities during inundations. Subsequently, these rasters were analysed and compared with an emphasis on differences within the individual geological study areas. The outputs showed clear differences in the individual hydrodynamic characteristics (e.g. the average inundation area during Q100 was 29.07% larger in the Flysch than in the Massif). Overall, the Flysch zone appeared to be far riskier in terms of flash floods than in the case of the Bohemian Massif.

Exploring the dynamics of a complex, slow-moving landslide in the Austrian Flysch Zone with 4D surface and subsurface information

Complex, slow-moving landslides are common in deeply weathered soils with clay-rich layers, as can be found in the Flysch Zone of Lower Austria. Complex process behaviour on differing spatio-temporal scales calls for long-term measurement series on both surface and subsurface parameters. Only then, dynamics and interrelations with possible triggering mechanisms might be further understood. This study investigates a small, slow-moving earth slide - earth flow system.Information on surface changes, based on digital elevation models (DEMs) of Difference (DoDs) using terrestrial laser scanning (TLS), is available since 2015 (2009, including ALS). Subsurface monitoring started in 2018. Data was analysed comparatively for overlapping periods: A conceptual subsurface model was generated with geotechnical information (penetration tests/ drill core samples), incorporating regolith thickness and potential shear surfaces. For four periods between 2018-11-14 and 2020-11-18 (∼2 years), interrelations of hydro-meteorological input data (precipitation/ temperature), changes in the spatio-temporal development of subsurface hydrology (piezometers), subsurface dynamics (inclinometer) and surface dynamics (DoDs) were analysed in detail.Total dynamics in the 2-year period were marginal. Total inclinometer displacements were max. ∼1.65 cm; these changes were too small to be depictable on the surface with TLS based DoDs. Nonetheless, several relations of present state and known former dynamics were found: Regolith thickness could be reasonably described via penetration tests, being relatively shallower in areas of known process activity. Interpolated shear surfaces based on drill core analyses, penetration tests and inclinometer data are highly simplified; nevertheless, they depict relations to locations of known activity with respect to depth and geometry. Locations of shallowest groundwater levels and highest fluctuations correspond with areas of recent minor and former larger dynamics. Inclinometer displacement rates exhibit relations to hydro-meteorological input data and are in locations known from former bigger process magnitudes.

Predictive Modelling of Landslide Susceptibility in the Western Carpathian Flysch Zone

Landslides are the most common geodynamic phenomenon in Slovakia, and the most affected area is the northwestern part of the Kysuca River Basin, in the Western Carpathian flysch zone. In this paper, we evaluate the susceptibility of this region to landslides using logistic regression and random forest models. We selected 15 landslide conditioning factors as potential predictors of a dependent variable (landslide susceptibility). Classes of factors with too detailed divisions were reclassified into more general classes based on similarities of their characteristics. Association between the conditioning factors was measured by Cramer’s V and Spearman’s rank correlation coefficients. Models were trained on two types of datasets—balanced and stratified, and both their classification performance and probability calibration were evaluated using, among others, area under ROC curve (AUC), accuracy (Acc), and Brier score (BS) using 5-fold cross-validation. The random forest model outperformed the logistic regression model in all considered measures and achieved very good results on validation datasets with average values of AUCval=0.967, Accval=0.928, and BSval=0.079. The logistic regression model results also indicate the importance of assessing the calibration of predicted probabilities in landslide susceptibility modelling.

Dynamic characterization of a slow-moving landslide system – Assessing the challenges of small process scales utilizing multi-temporal TLS data

Slow-moving landslides play an important role in both theoretical slope evolution and practical landslide hazard and risk research. Related dynamics therefore are of major interest, including the investigation of surficial changes. Yet, very slow process rates impede their quantitative analysis over short time periods, the actual change not uncommonly lying within the error margins of the respective methodological approaches. This study aims in investigating the surface dynamics of a small, retrogressive, slow-moving (cm-dm/a) earth slide-earth flow system in the Flysch Zone of Lower Austria via multi-temporal, high-resolution terrestrial laser scanning (TLS) data. 7 epochs covering a 10 years' observation period were utilized to apply both detailed morphological mapping and the computation of digital elevation models (DEMs) of difference (DoDs). Data was analysed to 1) determine and delineate (recently active) process areas, 2) to describe their characteristics, rates and tendencies comparatively via mapping and DoDs - but also 3) to assess the applicability of TLS regarding vegetation cover and to 4) evaluate the added value of this comparative approach when it comes to interpreting landslide dynamics on such detailed scale. Two small Subsystems of the respective landslide, I (~3300 m2) and II (2100 m2), exhibit the highest activity within the observation period. Results show 1) areas of changes in surface height correspond with changes in the distribution and characterization of morphological landslide features, indicating landslide activity. 2) Both Subsystems exhibit different results regarding the magnitude of changes in surface height (DoDs) and feature assembly (mapping), but show similarity regarding the frequency of both changes in surface height and feature evolution, identifying them as rotational and translational process types interrelated with the main landslide system. 3) Findings suggest TLS based DoD computations to be able to detect real surface change on detailed scale (0.05 m raster, ±0.05 error range, 0.05 m steps) in areas of optimum conditions regarding vegetation cover, but also that 4) real surface change could be assessed in areas of less optimum conditions (±020 m error range, 0.20 m steps) where real surface change was overshadowed by changes in vegetation cover via comparatively analysing both DoD and mapping results.

Changes in the radial growth of trees in relation to biogeomorphic processes in an old‐growth forest on flysch, Czechia

AbstractTree radial growth is influenced by individual tree abilities, climate, competition, disturbance regimes, as well as biogeomorphic processes – including biomechanical interactions between trees and soil. Trees are actively involved in hillslope dynamics, both responding to and affecting many (bio)geomorphic processes. Using dendrochronology, we studied feedbacks associated with tree–soil–landscape formation, specifically relationships between hillslope processes, biomechanical effects of trees in soils, tree microhabitat conditions and their morphological adaptations, in the flysch zone of the Carpathians. We visually evaluated stem shape, microhabitat conditions and the biomechanical effects of 1663 trees. Cores were taken in four growing directions from 224 individuals of European beech (Fagus sylvatica L.). In a set of 193 cross‐dated beeches, average tree‐ring widths and tree eccentricities in all directions were calculated and analysed in relation to the biogeomorphic impacts of trees. Some significant drivers of tree radial growth and sources of stem eccentricity were detected. The radial growth of trees on which deadwood was leaning was markedly limited. In contrast, trees with exposed roots expressed the highest growth rates. This clearly suggests that root exposure may not be an effect of ‘exogenous’ soil creep, but may rather result from individually intensifying tree growth due to fine‐scale disturbance dynamics. The response of biomechanical tree–soil interactions in tree radial growth weakened with increasing stem diameter, reflecting the stabilizing role of larger trees. The significance of calendar year on radial growth suggests seasonality in the dynamic component of soil creep. Tree eccentricity was observed mainly in the downslope direction, which suggests a relatively complex effect of biomechanics on stem tilting. © 2020 John Wiley &amp; Sons, Ltd.

Assessment of landslide susceptibility using statistical modelling in the flysch zone of the Western Carpathians (NW Slovakia)

ABSTRACT Landslides represent one of the most frequent geodynamic phenomena in Slovakia. This contribution focuses on the relations of the selected landscape attributes and landslides in flysch area of the Western Carpathians. We presented three statistical methods of assessing and making a prognosis of the landslide hazard: multivariate, factor and zonal analysis. These methods complement each other and their aim is to analyse and recognize natural processes, which trigger the landslides in a more complex way. With multivariate analysis, we evaluated mutual interactions between the input attributes and determined their level of impact on landslide hazard. Using factor analysis, we extracted latent factors with the highest factor loads and identified the main factors that could trigger landslides. Areal extension of landslides in individual landscape attributes was expressed by zonal analysis, based on the superposition of the individual vector layers. Our evaluation shows that the slope predisposition to landslides is predominantly given by the geological, hydrogeological and morphological conditions. The proposed landslide risk assessment procedure allows for the functional sustainable development of the landscape development planning documents. The results presented in this paper are relevant for the area formed by flysch rock (Alps and Carpathians), but also for areas where clastic sediments alternate rhythmically.

P–T–tevolution of the Cycladic Blueschist Unit in Western Anatolia/Turkey: Geodynamic implications for the Aegean region

AbstractEclogite and blueschist facies rocks occurring as a tectonic unit between the underlying Menderes Massif (MM) and the overlying Afyon Zone/Lycian Nappes and the Bornova Flysch Zone in western Anatolia represent the eastward continuation of the Cycladic Blueschist Unit (CBU) in Turkey. This high‐Punit is attributed to the closure of the Pindos Ocean and consists of (a) a Triassic to Upper Cretaceous coherent series derived from passive continental margin sediments and (b) the tectonically overlying Upper Cretaceous Selçuk mélange with eclogite blocks embedded in a pelitic epidote‐blueschist matrix. The coherent series has experienced epidote‐blueschist facies metamorphism (490 ± 25°C/11.5 ± 1.5 kbar; 38 km depth).40Ar/39Ar white mica and206Pb/238U monazite dating of quartz metaconglomerate from coherent series yielded middle Eocene ages of 44 ± 0.3 and 40.1 ± 3.1 Ma for epidote‐blueschist facies metamorphism, respectively. The epidote‐blueschist facies metamorphism of the matrix of the Selçuk mélange culminates at 520 ± 15°C/13 ± 1.5 kbar, 43 km depth, and is dated at 57.5 ± 0.3–54.5 ± 0.1 Ma (40Ar/39Ar phengite). Eclogite facies metamorphism of the blocks (570 ± 30°C/18 ± 2 kbar, 60 km depth) is early Eocene and dated at 56.2 ± 1.5 Ma by206Pb/238U zircon. Eclogites experienced a nearly isothermal retrogression (490 ± 40°C/~6 to 7 kbar) during their incorporation into the Selçuk mélange. The retrograde overprints of the coherent series (410 ± 15°C/7 ± 1.5 kbar from Dilek Peninsula and 485 ± 33°C/~6 to 7 kbar from Selçuk–Tire area) and the Selçuk mélange (510 ± 15°C/6 ± 1 kbar) are dated at 35.8 ± 0.5–34.3 ± 0.1 Ma by40Ar/39Ar white mica and 31.6 ± 6.6 Ma by206Pb/238U allanite dating methods, respectively. Regional geological constrains reveal that the contact between the MM and the CBU originally formed a lithosphere‐scale transform fault zone.40Ar/39Ar white mica age from the contact indicates that the CBU and the MM were tectonically juxtaposed under greenschist facies conditions during late Eocene, 35.1 ± 0.3 Ma.

The \u201cSalcher\u201d landslide observatory\u2014experimental long-term monitoring in the Flysch Zone of Lower Austria

Shallow landslide processes in geologically prone areas are recognised to pose threat to both human life and property. As precipitation is one of the main triggers for landslides, hydro-meteorological interrelationships and related future changes regarding frequency and magnitude of landslide processes in particular are of major interest. Long-term monitoring investigations of active landslide sites can provide a better understanding of the kinematic behaviour and triggering conditions of slope instabilities induced by hydro-meteorological patterns. In this study, we present the installation and first results of a long-term monitoring setup in the Flysch Zone of Lower Austria equipped with a large variety of combined hydrological and geotechnical measuring techniques. The geological unit of the Flysch Zone, characterised by high contents of clay and the corresponding weathering products, is exceptionally prone to earth and debris slides which are mostly triggered by heavy precipitation events or snow melting. The landslide under investigation is situated in the heterogeneous lithology of Flysch deposits, surrounded by private property and without any agricultural usage. There is evidence of landslide activity since the 1950s. As it is showing only moderate displacement velocities (max. 20 cm in 2009), it represents a predestined study site for a long-term monitoring and the testing of new monitoring techniques. One of the main aims of this study is to characterise the internal structure, assess the current landslide dynamics and to analyse recent process activity by means of surface and subsurface monitoring installations. Surface methods currently include terrestrial laser scanning, GNSS and total station measurements. With these, surface movement rates of approx. 12 cm/6 months have been detected in the most active part of the landslide. Inclinometer measurements together with results from core drillings and penetrations tests suggest a complex, rotational landslide system with different shear zones, consisting of a more active part in the upper 3 m underlain by a less active part down to 9-m depth. As this monitoring site is designed to be operated for at least 10 years, information about its structure and high-resolution, multi-temporal data about its dynamics can be correlated with hydrological cause variables in the future. These insights and the exemplary nature of the study site regarding shallow landslide processes in Flysch deposits will be useful for the development of novel analysis methods for both Lower Austria as well as study sites with similar initial conditions.

Landsliding as a Limit to Possible Territorial Development in the Kysuce Region

Abstract The growing development of settlements in mountainous areas and their sustainable development constantly requires new approaches to assess the land in terms of occurrence of landslides. The flysch zone, where the monitored area is located, is one of the most landslide prone areas in Slovakia. Landslides respond sensitively to the quality of the individual factors that form the landscape and to the change of natural conditions. Their occurrence is a geo-barrier that reduces or totally prevents the use of natural environment and negatively affects the life of population and territorial development. The reason for the increased hazard of landslides is not only demographic pressure on territories, but also its poor management. Consistent spatial planning addresses not only the spatial layout but also the functional use of the territory. Landslides represent one of the limits of land use. This study is based on the assessment of landsliding as a limit to possible territorial development. The input parameters for the assessment were elements of the current landscape structure (built up structure, forest stands, transitional woodland-shrubs, traditional agricultural land, permanent grasslands and arable land) and occurring landslides (active, potential and stabilized). On most of the determined elements of the landscape, landslides occur on about a quarter of their area. They have a smaller share only in areas of mixed forests, built up areas and have the smallest share on arable land. Potential landslides have the largest proportion on all landscape elements. They occupy the largest areas on coniferous forests (1578.93 ha) and on permanent grasslands (741.33 ha). By evaluating the overall endangerment of the area by landslides according to the degree of threat, we found that the greatest threat of landslides is in the Skalité and Svrčinovec cadastral areas, the smallest threat is in the Čadca cadastral area. In addition to the danger of landsliding in the individual elements of the landscape, we have also set limits for its development. Spatial planning limits have been divided into two categories according to the sectors they affect the most: limiting the development of an area assigned for residential building, or restricting the development of an area designed for agricultural and forestry purposes.

The deepest Moho in the Western Carpathians and its respective crustal density model (CEL12 section)

Abstract The main aim of this study is to compile 2-D density model of the CELEBRATION 2000 profile CEL12, which is based on seismic refraction data. The profile CEL12 crosses the External Western Carpathians Flysch zone and is located in the southern part of Poland. The general feature of the resultant density model shows significant changes in the crustal thickness. The Moho depth changes in the interval from 31 km to 43 km. The interpreted 43 km crustal thickness over a 60 km section of the profile results in the discovery of an area, which represents the thickest crust in the entire West Carpathians. This area is situated ~50 km north-east from the High Tatras in Poland.

Provenance and palaeogeographic evolution of Lower Miocene sediments in the eastern North Alpine Foreland Basin

Detrital heavy mineral analysis and sediment chemistry of Lower Miocene sediments of the Lower Austrian Northern Alpine Foreland Basin generally indicate provenance from metapelitic source rocks. The sediments of the Traisen Formation (Ottnangian) were primarily derived from Alpine sources such as the Austroalpine crystalline units of the Eastern Alps and reworked and eroded siliciclastics strata on top of the Northern Calcareous Alps and, in addition, low-grade metamorphic rocks of the Bohemian Massif. Ottnangian and Karpatian sediments in the subground of the northern Lower Austrian Molasse basin were mainly fed from the same southern sources, from low-grade metamorphic rocks of the Bohemian Massif and via resedimentation of Lower Miocene and Palaeogene of the Waschberg–Ždanice Unit and the Vienna Basin. A large-scale input of material from the Rhenodanubian Flysch Zone and of higher-grade metamorphic units and granites of the Bohemian Massif in the Lower Miocene Molasse basin can be ruled out. A compilation of well sections and heavy mineral data point to the existence of a partly emerged, N–S oriented ridge during the Egerian.

Palaeomagnetic time and space constraints of the Early Cretaceous Rhenodanubian Flysch zone (Eastern Alps)

The Rhenodanubian Flysch zone (RDF) is a Lower Cretaceous-lower Palaeocene turbidite succession extending for similar to 500 km from the Danube at Vienna to the Rhine Valley (Eastern Alps). It consists of calcareous and siliciclastic turbidite systems deposited in a trench abyssal plain. The age of deposition has been estimated through micropalaeontologic dating. However, palaeomagnetic studies constraining the age and the palaeolatitude of deposition of the RDF are still missing. Here, we present palaeomagnetic data from the Early Cretaceous Tristel and Rehbreingraben Formations of the RDF from two localities in the Bavarian Alps (Rehbrein Creek and Lainbach Valley, southern Germany), and from the stratigraphic equivalent of the Falknis Nappe (Liechtenstein). The quality of the palaeomagnetic signal has been assessed by either fold test (FT) or reversal test (RT). Sediments from the Falknis Nappe are characterized by a pervasive syntectonic magnetic overprint as tested by negative FT, and are thus excluded from the study. The sediments of the Rehbreingraben Formation at Rehbrein Creek, with positive RT, straddle magnetic polarity Chron M0r and the younger M'-1r' reverse event, with an age of similar to 127-123 Ma (late Barremian-early Aptian). At Lainbach Valley, no polarity reversals have been observed, but a positive FT gives confidence on the reliability of the data. The primary palaeomagnetic directions, after correction for inclination shallowing, allow to precisely constrain the depositional palaeolatitude of the Tristel and Rehbreingraben Formations around similar to 28 degrees N. In a palaeogeographic reconstruction of the Alpine Tethys at the Barremian/Aptian boundary, the RDF is located on the western margin of the Brianconnais terrain, which was separated from the European continent by the narrow Valais Ocean.

Lower Badenian coarse-grained Gilbert deltas in the southern margin of the Western Carpathian Foredeep basin

AbstractTwo coarse-grained Gilbert-type deltas in the Lower Badenian deposits along the southern margin of the Western Carpathian Foredeep (peripheral foreland basin) were newly interpreted. Facies characterizing a range of depositional processes are assigned to four facies associations — topset, foreset, bottomset and offshore marine pelagic deposits. The evidence of Gilbert deltas within open marine deposits reflects the formation of a basin with relatively steep margins connected with a relative sea level fall, erosion and incision. Formation, progradation and aggradation of the thick coarse-grained Gilbert delta piles generally indicate a dramatic increase of sediment supply from the hinterland, followed by both relatively continuous sediment delivery and an increase in accommodation space. Deltaic deposition is terminated by relatively rapid and extended drowning and is explained as a transgressive event. The lower Gilbert delta was significantly larger, more areally extended and reveals a more complicated stratigraphic architecture than the upper one. Its basal surface represents a sequence boundary and occurs around the Karpatian/Badenian stratigraphic limit. Two coeval deltaic branches were recognized in the lower delta with partly different stratigraphic arrangements. This different stratigraphic architecture is mostly explained by variations in the sediment delivery and /or predisposed paleotopography and paleobathymetry of the basin floor. The upper delta was recognized only in a restricted area. Its basal surface represents a sequence boundary probably reflecting a higher order cycle of a relative sea level rise and fall within the Lower Badenian. Evidence of two laterally and stratigraphically separated coarse-grained Gilbert deltas indicates two regional/basin wide transgressive/regressive cycles, but not necessarily of the same order. Provenance analysis reveals similar sources of both deltas. Several partial source areas were identified (Mesozoic carbonates of the Northern Calcareous Alps and the Western Carpathians, crystalline rocks of the eastern margin of the Bohemian Massif, older sedimentary infill of the Carpathian Foredeep and/or the North Alpine Foreland Basin, sedimentary rocks of the Western Carpathian/Alpine Flysch Zone).

SHALLOW HYDROCARBON INDICATIONS ALONG THE ALPINE THRUST BELT AND ADJACENT FORELAND BASIN: DISTRIBUTION AND IMPLICATIONS FOR PETROLEUM EXPLORATION

Shallow oil and gas shows are common in the Alpine thrust front (including the Flysch Zone) and the North Alpine Foreland Basin in Switzerland, southern Germany and Austria, but have not hitherto been evaluated systematically. In the vertically‐drained Vienna Basin and the easternmost part of the Flysch Zone, shallow oil and gas shows and seeps often coincide with deeper‐lying hydrocarbon accumulations, and gas shows occur along major faults – for example within the urbanised area of the city of Vienna. The number of gas shows decreases in the Vienna Basin away from (to the south of) the subcrop of the main thermogenic source rock (the Upper Jurassic Mikulov Formation); however shallow accumulations of microbial gas occur in that area. To the west, along the northern margin of the laterally‐drained North Alpine Foreland Basin, oil shows have been recorded in both Austria and Switzerland; microbial gas shows are common in addition to thermogenic hydrocarbons. Typically the shows form regional clusters along river valleys and occur above shallow gas accumulations.A Lower Oligocene organic‐rich interval represents the main source of oil / condensate and thermogenic gas in the Upper Austrian part of the North Alpine Foreland Basin, whereas the composition of oil shows within the Calcareous Alps to the south indicates the presence of mature Mesozoic source rocks within the Alpine nappes. This implies the presence of an additional, as‐yet untested petroleum system. Thermogenic gas, occurring in Permo‐Triassic evaporitic rocks in the Calcareous Alps, as well as microbial gas in younger sediments, has frequently been encountered during salt mining and tunnelling activities.A surprising discrepancy has been found in different parts of the study area between the number of hydrocarbon shows and the number of economic fields. Whereas the number of fields and shows are approximately in proportion in the Vienna Basin and the Austrian sector of the North Alpine Foreland Basin, shows appear to be “under‐represented” in Germany. By contrast in Switzerland, despite a high number of shows especially in the North Alpine Foreland Basin and the Jura fold‐and‐thrust belt, no economic production has been established to date. Future exploration will show whether this is due to poor reservoir/trap quality, or if undiscovered resources are in fact present. The presence of oil shows generated from Mesozoic and Oligocene source rocks in the SW German and Swiss parts of the North Alpine Foreland Basin suggests the occurrence of multiple petroleum systems; these systems should be delineated in future studies.Few surface seeps have been recorded in less populated parts of the study area such as the high Alps, possibly due to sampling bias. However, this bias does not explain the low frequency of recorded hydrocarbon shows in the German part of the North Alpine Foreland Basin. This may be because the geological setting there is in general less favourable for the migration of thermogenic gas into shallow reservoirs and its preservation in shallow traps.

Conceptual model of the Gülbahçe geothermal system, Western Anatolia, Turkey: Based on structural and hydrogeochemical data

The Gülbahçe Geothermal Field is located on the eastern margin of the Karaburun Peninsula, about 45km from the city of İzmir, western Anatolia, Turkey. The stratigraphy of the study area is represented by a Miocene volcano-sedimentary succession, including several sedimentary and volcanic units. These units overlie the basement rocks of the Karaburun Platform and Bornova Flysch Zone which consist of sandstones, shales and carbonate blocks. These rock units are cut and deformed by a series of NW-SE- to NE-SW-trending faults, extending from Sığacık Bay to Gülbahçe Bay. Structural studies suggest that while most of the geothermal systems in western Anatolia are controlled by normal faults, the geothermal system at Gülbahçe is controlled by a strike-slip dominated shear zone, previously named the İzmir-Balıkesir Transfer Zone. Along the fault zone, associations of active fault segments accommodate deep circulation of hydrothermally modified sea water, and thus the resulting negative flower structure is the primary control mechanism for the geothermal system.Hydrogeochemical properties of the field show that surface temperature of fluid ranges from 30 to 34°C. Geothermal fluids in Gülbahçe have high salinity (EC>34 mS/cm) and low enthalpy. Piper and Schoeller diagrams indicate that geothermal fluid is in the NaCl facies. Chemical geothermometers suggest that the reservoir temperature is around 53–136°C. The isotopic data (oxygen-18, deuterium and tritium) suggest that geothermal fluids are formed by local recharge and deep circulation of sea water.

Geochemistry and origin of Dehoo manganese deposit, south Zahedan, southeastern Iran

Dehoo manganese deposit is located 52 km to the south of Zahedan in Sistan and Baluchestan Province, southeastern Iran. This deposit that lies in the central part of the Iranian Flysch Zone is lenticular in shape and lies above the micritic limestone-radiolarite cherts of the upper Cretaceous ophiolite unit. It is hosted within the reddish to brown radiolarite cherts and in places interlinks with them, so that the radiolarite chert packages play a key role for Mn mineralization in the region. Investigated ore-paragenetic successions and the geochemical characteristics of the Dehoo deposit were studied by means of major oxide, trace, and rare earth element (REE) contents that provide information as to the mineral origin. Strong positive correlations were found between major oxides and trace elements (Al2O3-TiO2, r = 0.95; TiO2-MgO, r = 0.94; Fe2O3-Al2O3, r = 0.90; MgO-Al2O3, r = 0.84; MgO-Fe2O3, r = 0.88; Fe2O3-TiO2, r = 0.91; Fe2O3-K2O, r = 0.74; Al2O3-K2O, r = 0.69; Al2O3-V, r = 0.72; TiO2-V, r = 0.73, and MgO-V, r = 0.69) that testify to the contribution of mafic terrigenous detrital material to the deposit. Chondrite-normalized REE patterns of all ore samples are characterized by negative Ce (0.06–0.15, average 0.10) and slightly positive Eu (0.29–0.45, average 0.36) anomalies. Based on ratios of Mn/Fe (average 56.23), Co/Ni (average 0.33), Co/Zn (average 0.38), U/Th (average 3.40), La/Ce (average 1.45), Lan/Ndn (average 2.16), Dyn/Ybn (average 0.33), and light REE/heavy REE (average 8.40; LREE > HREE), as well as Ba (average 920 ppm) and total REE contents (average 6.96 ppm) negative Ce and positive Eu anomalies, Dehoo could be considered a predominantly submarine hydrothermal Mn deposit complemented by terrigenous detrital mafic material.

Formation conditions of Upper Eocene olistostromes and retro-overthrusts at the southern slope of the Greater Caucasus

The paper considers age, formation conditions, and tectonic setting of Upper Eocene olistostromes of the southern slope of the Greater Caucasus. The formation of olistostromes resulted from the contribution of coarse-clastic material to the Late Eocene basin, which was related to the erosion of thrusted sheets of the Racha–Vandam cordillera of the Gagra–Java zone of the southern slope of the Greater Caucasus and concomitant multiple catastrophic landslide processes. In the Early Pliocene (Rodanian folding phase), Upper Eocene olistostromes along with nappes of the flysch zone were thrust to the south. In the pre- Quaternary (Valakh) folding phase, due to intense shortening, olistostromes in the frontal part of nappes were squeezed, displaced to the north, and thrust with the formation of retro-overthrust, fragments of which remain as isolated blocks (klippen) inside the flysch zone.