Forest soils are an important component of the global C cycle as they store large amounts of organic carbon (OC). Particularly in mountain forest ecosystems, soil organic matter is of crucial ...importance for site productivity and ecosystem services, but probably sensitive to climate change. Robust information about the OC stocks of mountain soils is rare due to their limited accessibility and large spatial heterogeneity. Our study covered the entire German Alps in a large-scale sampling campaign in 2011 and 2012, and provides soil organic carbon (SOC) stock data obtained from 150 forest soil profiles with different site conditions (elevation, aspect, air temperature, precipitation, parent material, soil type) and different intensities of historical forest utilization. The mean SOC stock of the investigated soils is 10.9kgm−2. The median value is 9.6kgm−2, indicating a skewed distribution of SOC stocks in forest soils of the German Alps. On average, 30% of the SOC stock is bound in the organic surface (O) layer, and 70% in the mineral soil. SOC stocks show a considerable dependency on site conditions (elevation, air temperature, precipitation, parent material). Soils in the German Limestone Alps show a significant OC stock gradient from W (Werdenfels) to E (Berchtesgaden region), which probably has been caused by more intense historical forest utilization in the latter compared to the former region. Soils at high-elevation sites with low air temperature and high precipitation have particularly large OC stocks. However, the elevation and climate effect is statistically significant only for precipitation due to the large variation of other factors with relevance for SOC stocks (e.g. parent material, soil type) in a given elevation/climate stratum. Histosols on consolidated calcareous bedrock and Histic Rendzic Leptosols have significantly larger SOC stocks than Rendzic Leptosols, Rendzic Cambisols, or soils on easily-weatherable parent material (marl, clayey sandstone, moraine). The fact that SOC stocks in forest soils of the German Alps are by trend larger at high-elevation sites with low air temperature and high precipitation suggests a sensitivity to the ongoing climate change and a risk of SOC losses for the predicted climate scenarios.
•SOC stocks of forest soils in the German Alps are on average 10.9kgm−2.•Highly skewed distribution; majority of soils have SOC stocks <8kgm−2.•Less SOC in Eastern German Alps, where historical forest utilization was intensive.•SOC stocks are dependent on site elevation, air temperature and precipitation.•SOC stocks are sensitive to the ongoing climate change.
We investigate the tectonic evolution of the Wetterstein and Mieming mountains in the western Northern Calcareous Alps (NCA) of the European Eastern Alps. In-sequence NW-directed stacking of thrust ...sheets in this thin-skinned foreland thrust belt lasted from the Hauterivian to the Cenomanian. In the more internal NCA major E-striking intracontinental transform faults dissected the thrust belt at the Albian–Cenomanian boundary that facilitated ascent of mantle melts feeding basanitic dykes and sills. Afterwards, the NCA basement was subducted, and the NCA were transported piggy-back across the tectonically deeper Penninic units. This process was accompanied by renewed Late Cretaceous NW-directed thrusting, and folding of thrusts. During Paleogene collision, N(NE)-directed out-of-sequence thrusts developed that offset the in-sequence thrust. We use this latter observation to revise the existing tectonic subdivision of the western NCA, in which these out-of-sequence thrusts had been used to delimit nappes, locally with young-on-old contacts at the base. We define new units that represent thrust sheets having exclusively old-on-young contacts at their base. Two large thrust sheets build the western NCA: (1) the tectonically deeper Tannheim thrust sheet and (2) the tectonically higher Karwendel thrust sheet. West of the Wetterstein and Mieming mountains, the Imst part of the Karwendel thrust sheet is stacked by an out-of-sequence thrust onto the main body of the Karwendel thrust sheet, which is, in its southeastern part, in lateral contact with the latter across a tear fault.
This study summarizes and provides new data concerning the composition, fabrics, depositional environment and palaeogeographic distribution of Upper Jurassic–lowermost Cretaceous ...(Kimmeridgian–Berriasian) upper slope build-ups with complex microencruster-microbialite-calcified sponge frameworks associated with large amount of early marine cement crusts. The focus is on reef carbonates from the Štramberk-type limestones from the Carpathians (Getic Carbonate Platform) and Apuseni Mountains in Romania, with additional data from the Plassen Carbonate Platform (Northern Calcareous Alps, Austria) and the Štramberk Carbonate Platform (Western Carpathians, Czech Republic and Poland). The microencrusters, often of problematic biological affinity, are mainly Crescentiella morronensis (Crescenti 1969), Labes atramentosa Eliášová 1986 and Radiomura cautica Senowbari-Daryan & Schäfer 1979. Specialized encrusting calcified sponges are also common, with Perturbatacrusta leini Schlagintweit & Gawlick 2011 as the most abundant and characteristic form. Light-dependent microencrusters (e.g., “Lithocodium-Bacinella”) that are abundant in coeval overlying coral-dominated reefs, are rare, as are corals (microsolenids adapted to low-light level). Three dominant types of fabric-based framework varieties are considered for the studied build-ups. The main differences between these types reflect a bathymetric zonation in their development. The abundance of Crescentiella, microbialites, massive radiaxial fibrous cement crusts, and poorly diversified microencruster/sponge assemblages, are all suggesting that Type I framework variety is characteristic for build-ups formed in the deepest parts of an upper slope environment. Type II most probably developed at slightly lower depths than Type I, as revealed by its main features (clusters of calcified sponges and microencrusters associated with less extensive cement crusts) and distribution between the other two types in the sedimentary sequences. Type III, the most common, characterizes build-ups formed at the shallowest depths of the upper slope environment and is composed of alternating layers of diverse microencrusters (including several light-dependent species), calcified sponges, rare microsolenid corals, microbialites and early marine cement crusts. The distribution patterns of these framework varieties (Type I to Type III) together with their associated facies, strengthen this depositional interpretation. From a process-based perspective, these upper slope build-ups exemplify triple hybrid carbonates which are intimate combinations of microbial and skeletal components (microencrusters/microbialites and calcified sponges), associated with abiotic precipitates (early marine cement crusts). Their palaeogeographic importance is reflected in their formation on the slopes of rimmed carbonate platform systems facing open oceanic domains, predominantly within the central Western Tethys Realm. Such hybrid build-ups appear to have been absent on the southern European shelf where other reef frameworks commonly developed on carbonate ramps and ramp-type carbonate platforms.
•Recognition of Upper Jurassic–lowermost Cretaceous hybrid build-ups in the Western Tethys Realm.•Establishment of three main types of microencruster-microbialite-calcified sponge framework based on microfabric diversity.•Identification of key-elements for the recognition of carbonate platforms with the microbial factory on their slopes.•Implications for palaeogeographic reconstructions of the central-Western Tethys Realm.
Shear zones – A review Fossen, Haakon; Cavalcante, Geane Carolina G.
Earth-science reviews,
August 2017, 2017-08-00, Letnik:
171
Journal Article
Recenzirano
Strain in the lithosphere localizes into tabular zones known as shear zones that grow from small outcrop-size individual zones to large composite structures. Nucleation is related to distributed ...microscale flaws or mesoscale structures such as fractures and dikes, and they soon establish displacement profiles similar to faults. Also similar to faults, they grow in width and length primarily by segment linkage as they accumulate strain and displacement, and this process typically results in shear zone networks. Consequently, mature shear zones are heterogeneous and composite zones characterized by anastomosing patterns and local variations in thickness and finite strain. Kinematic vorticity estimates suggest that most shear zones deviate from simple shear, and even if subsimple shear may be a useful reference model in many cases, finite strain data indicate that many shear zones involve three-dimensional combinations of coaxial and non-coaxial deformation, such as transpression and transtension. Strain geometry and kinematic vorticity can vary significantly within shear zone networks, which makes it difficult to estimate the bulk deformation type for a composite shear zone or shear zone network. However, perhaps the most challenging aspect is that of progressive deformation, i.e. to what extent and how flow parameters change during deformation (non-steady state deformation), which needs to be addressed by a combination of detailed field observations and numerical modeling.
We present a map that correlates tectonic units between Alps and western Turkey accompanied by a text providing access to literature data, explaining the concepts used for defining the mapped ...tectonic units, and first-order paleogeographic inferences. Along-strike similarities and differences of the Alpine-Eastern Mediterranean orogenic system are discussed. The map allows (1) for superimposing additional information, such as e.g., post-tectonic sedimentary basins, manifestations of magmatic activity, onto a coherent tectonic framework and (2) for outlining the major features of the Alpine-Eastern Mediterranean orogen. Dinarides-Hellenides, Anatolides and Taurides are orogens of opposite subduction polarity and direction of major transport with respect to Alps and Carpathians, and polarity switches across the Mid-Hungarian fault zone. The Dinarides-Hellenides-Taurides (and Apennines) consist of nappes detached from the Greater Adriatic continental margin during Cretaceous and Cenozoic orogeny. Internal units form composite nappes that passively carry ophiolites obducted in the latest Jurassic–earliest Cretaceous or during the Late Cretaceous on top of the Greater Adriatic margin successions. The ophiolites on top of composite nappes do not represent oceanic sutures zones, but root in the suture zones of Neotethys that formed after obduction. Suturing between Greater Adria and the northern and eastern Neotethys margin occupied by the Tisza and Dacia mega-units and the Pontides occurred in the latest Cretaceous along the Sava-İzmir-Ankara-Erzincan suture zones. The Rhodopian orogen is interpreted as a deep-crustal nappe stack formed in tandem with the Carpatho-Balkanides fold-thrust belt, now exposed in a giant core complex exhumed in late Eocene to Miocene times from below the Carpatho-Balkan orogen and the Circum-Rhodope unit. Its tectonic position is similar to that of the Sakarya unit of the Pontides. We infer that the Rhodope nappe stack formed due to north-directed thrusting. Both Rhodopes and Pontides are suspected to preserve the westernmost relics of the suture zone of Paleotethys.
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•Tectonic map correlates tectonic units between Alps and western Turkey.•Profiles visualize architecture of Alpine-eastern Mediterranean orogens.•Review provides overview of Alpine-type orogens across national boundaries.
The general chronological outline of the Last Glacial Maximum (LGM) in the Alps is well known after more than two centuries of ice age research in Europe. Current studies focus on resolving the ...details of the deglaciation process after the LGM. Particularly few data in this context are available from the High Alps. Here we report chronological constraints on the onset of deglaciation in two different study areas from the Western and Eastern Alps: the Mont Blanc (Italy) and Zillertal Alps (Austria). We sampled 32 bedrock and boulder surfaces from high elevation ridges beneath the glacial trimline. The oldest 10Be exposure ages of ∼18.5 ka correspond to the initiation of lowering of the LGM ice surface. Identical ages from both study areas suggest synchronous decay of the LGM glaciers in the accumulation zones of the Western and Eastern Alps. Thus, the High Alpine ice surface lowered roughly synchronously to the downwasting of the glacier tongues in the forelands that was completed 19–18 ka. In both study areas, ages of numerous samples that are consistently 2–3 ka younger than 18.5 ka suggest the persistance of remnant ice patches at high elevations in the Lateglacial accumulation zones approximately until the Bølling-Allerød interstadial.
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•Determination of initial lowering of LGM ice surface in the High Alps.•Trimline dating in two study sites: Mt. Blanc (Italy) and Zillertal Alps (Austria).•Lowering starts simultaneously at ∼ 18.5 ka in both study sites.•Synchronous with significant retreat of the piedmont lobes soon after 19 ka.•Rapid decay of LGM ice cover (∼1 km/1–2 ka) in the center of the Alps.
Unraveling the age and kinematics of low temperature deformation events is crucial in understanding the late‐stage evolution of orogens. However, accurate age constraints can often be challenging to ...obtain due to unideal outcrop conditions, large sedimentary hiatuses or the lack of well‐defined thermal events. In this study, we show on the example of the Nekézseny Thrust, a poorly exposed late orogenic thrust in the southern Western Carpathians, that a combined approach of structural analysis and multi‐method thermochronology can provide the necessary temporal, kinematic and thermal constraints for a detailed reconstruction of the deformation history. While structural mapping revealed that the Late Cretaceous Uppony Gosau Basin in the footwall of the Nekézseny Thrust underwent a significant post‐Campanian and pre‐Miocene shortening, K/Ar dating of fault gouge samples from the main fault zone constrained the primary thrusting event to the Maastrichtian. Based on the acquired apatite fission‐track and (U‐Th)/He ages, subsequent heating of the Upper Cretaceous sediments due to tectonic burial was limited to 75–100°C, followed by deformation‐related and gradual cooling between the Eocene and Early Miocene. Considering the reconstructed deformation history, as well as the large‐scale tectonic affinity of the displaced units in its footwall and hanging wall, the Nekézseny Thrust is a far‐traveled (ca. 600 km) segment of the Late Cretaceous Alps‐Dinarides contact zone, whose development was linked to the switch from lower plate to upper plate position with respect to the Sava Zone and Alpine Tethys sutures, respectively.
Key Points
Detailed structural analysis is combined with three thermochronological methods to reconstruct low temperature deformation events
K/Ar age of fault gouges date the fault activity directly, while apatite fission‐track and (U‐Th)/He data constrain the exhumation history
The Maastrichtian age of the Nekézseny Thrust is interpreted in lights of the late‐stage Alpine‐Carpathian‐Dinaric tectonic evolution
Rocky desertification, which is relatively less well known than desertification, refers to the processes and human activities that transform a karst area covered by vegetation and soil into a rocky ...landscape. It has occurred in various countries and regions, including the European Mediterranean and Dinaric Karst regions of the Balkan Peninsula, Southwest China on a large scale, and alarmingly, even in tropical rainforests such as Haiti and Barbados, and has had tremendous negative impacts to the environment and social and economic conditions at local and regional scales. The goal of this paper is to provide a thorough review of the impacts, causes, and restoration measures of rocky desertification based on decades of studies in the southwest karst area of China and reviews of studies in Europe and other parts of the world. The low soil formation rate and high permeability of carbonate rocks create a fragile and vulnerable environment that is susceptible to deforestation and soil erosion. Other natural processes related to hydrology and ecology could exacerbate rocky desertification. However, disturbances from a wide variety of human activities are ultimately responsible for rocky desertification wherever it has occurred. This review shows that reforestation can be successful in Southwest China and even in the Dinaric Karst region when the land, people, water, and other resources are managed cohesively. However, new challenges may arise as more frequent droughts and extreme floods induced by global climate change and variability may slow the recovery process or even expand rocky desertification. This review is intended to bring attention to this challenging issue and provide information needed to advance research and engineering practices to combat rocky desertification and to aid in sustainable development.
The most recent and complete French glacier inventory was previously the Vivian database, dating from the end of the 1960s but incorporated in the World Glacier Inventory database at the end of the ...1990s. Because of the important changes in glacier extent over recent decades an update of the inventory of glaciers of the French Alps was made in a digital vector format (with the associated database) for several dates covering the last 40years. Such a multitemporal glacier inventory matches a key demand of the Global Terrestrial Network for Glaciers and the Global Land Ice Measurements from Space initiative (GLIMS). Topographical maps, aerial photographs and satellite images were used to map the extent of glaciers using both manual and automatic methods; and the database was generated considering the design of the GLIMS database. Glaciers in the French Alps covered 369km2 in 1967/71, 340km2 in 1985/86, 300km2 in 2003, and 275km2 in 2006/09. This represents a decrease in surface area of about 25% over the entire study period. Acceleration in glacier shrinkage during the study period was revealed, probably linked to the increase in average air temperature in the 20th century, which has been particularly pronounced since the 1970s. The behaviour of glaciers of the French Alps is in agreement with that of glaciers observed by other studies across the European Alps. We also report the distribution of the morpho-topographic variables (aspect, elevation, etc.) of glaciers of the French Alps for the period 2006/09, and analyse changes of these variables in the last four decades.
•We realize the first multitemporal inventory of the glaciers in the French Alps.•We show that glacier extent decrease by 25% between 1967–71 and 2006–09.•Glacier shrinkage greatly increases during the period 1985–86 to 2006–09.•Shrinkage of the French Alpine glaciers is in agreement with other Alpine glaciers.•Shrinkage of the French Alpine glaciers is linked with air temperature increase.
The Late Jurassic Chenaillet ophiolitic complex (Western Alps) represents parts of an oceanic core-complex of the Liguria-Piemonte domain. A model for the origin and evolution of the Chenaillet ...ophicalcites based on textural and isotopic characterization is presented. The Chenaillet ophicalcites correspond to brecciated serpentinized peridotites that record seafloor shallow serpentinization at a minimum temperatures of 150°C followed by authigenic carbonation. Carbonation starts with a network of micrometric to millimetric pre- or syn-clast formation calcite veins accompanied by a pervasive carbonation of residual olivine and serpentine inside the serpentinite mesh core. A matrix of small calcite (<50μm, 12μm in average) cemented clasts after their individualization. Texture of the breccia, grain size distribution within the matrix, and chrysotile clusters support rapid cementation from a strongly oversaturated fluid due most likely to hydrothermal fluid cooling and decompression. Later fluids infiltrated by multiple crack formation and some dolomite locally formed along serpentinite-calcite interfaces. Carbonates have δ13C (VPDB) values that range between −5‰ and +0.4‰. The lower values were obtained for calcite within the serpentinite clasts. The δ18O (VSMOW) values have a range between +11‰ and +16‰ in carbonated clasts. The δ18O values in the matrix are fairly homogeneous with an average at +12‰ and the late calcite veins have values between +12.5 and +15.5‰. These values suggest a relatively high temperature of formation for all the carbonates. Carbonates within clast are mainly characterized by a formation temperature in the range of 110°C to 180°C assuming a δ18O value of seawater of 0‰, the matrix forms at a temperature of ca. 165°C. Late veins are characterized by a formation temperature ranging between 120and 155°C. We propose a model where serpentinization is followed by discrete carbonation then brecciation and cementation as a consequence of continuous hydrothermal fluid circulation in the serpentinite basement. This is comparable to observations made in the stockwork of present-day long-lived oceanic hydrothermal systems.
•The Chenaillet ophicalcites were formed in oceanic hydrothermal system.•Ophicalcites recorded serpentinization at a minimum temperatures of155°C.•Multistep serpentinite carbonation occurred at temperature ranging from 180 to 110°C during mantle rock exhumation.•Breccia cementation is fast and marked by calcite (± chrysotile) matrix precipitation.
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