The end-Permian mass extinction (EPME; ca. 251.94 Ma) is the most severe mass extinction in the geological record. Detailed paleobiological investigations show a very rapid EPME event, and recently ...published δ238U data show a large negative excursion and thus a massive shift to globally expanded anoxia at the main extinction phase in the latest Permian. The negative shift in δ238U is in correlation with a globally characterized negative δ13C excursion near the Permian-Triassic boundary (PTB). In some highly expanded PTB carbonate sections, however, there are two distinct negative δ13C excursions whereas uranium isotopes (δ238U) from such sections have not yet been examined, leaving a gap in the understanding of the global perturbations of marine redox conditions immediately following the EPME. Here, we present a new δ238U study of syn-depositional dolostones from a well-characterized and highly expanded drill core, which recorded two pronounced negative δ13C excursions across the PTB, from the Carnic Alps, Austria. This drill core extends 331-meters across the PTB and provides a unique opportunity to explore the detailed timing, duration, and extent of marine redox chemistry changes before, during, and immediately after the EPME. Our new δ238U record shows two negative shifts, which are correlated with the two negative δ13C excursions. The first negative δ238U excursion preceding the EPME confirms the recently published δ238U records from across the EPME and support that syndepositional marine dolostones can record δ238U trends of seawater similar to that of limestones. Modeling of uranium isotope cycling in the latest Permian and earliest Triassic oceans suggests two distinct stages of expanded marine anoxia separated by a brief interval (∼100 kyr) of reoxygenation across the PTB. The first anoxic episode lasted for ∼ 60 kyr while anoxic seafloor area expanded to cover >18% of the entire seafloor, coeval with the main EPME horizon, agreeing with marine anoxia as a proximate kill mechanism for the EPME. The second anoxic event was less intense compared to the first anoxic pulse but sustained for a longer duration. A global modeling of coupled C, P, and U cycles show that two pulses of volcanic carbon injection that drives global warming and increased phosphorus weathering rate can reasonably reproduce our data to match two phases of anoxia. The model also demonstrates that the loss of terrestrial vegetation in the EPME is crucial to generating an intervening interval of oxygenated ocean. Our new study adds to a growing body of evidence that the global marine redox conditions underwent rapid oscillations during the EPME event and continued afterward, which may have played a central role in delaying the marine ecosystem recovery in the Early Triassic.
The kinematic acceleration of rock glaciers observed in recent decades shows that the behavior of these landforms is related to climate change. Velocity variations on yearly to seasonal time scales ...are frequently investigated, but velocity changes measured on shorter time scales (i.e., on hourly resolutions) are as yet poorly investigated. We used a ground based synthetic aperture radar to investigate, on an hourly time scale, the displacement of a rock glacier located in Val Senales (European Alps, northern Italy). We observed velocity fluctuations occurring at a very regular pace, characterized by phases of sharp acceleration (up to 0.9 mm/hr) lasting 4–11 hr followed by long phases of stagnation lasting 13–20 hr. This study describes an unprecedented observation of an hourly velocity rhythm of an active rock glacier and opens up new perspectives in the analysis and interpretation of rock glacier kinematics.
Plain Language Summary
Rock glaciers are debris landforms commonly found in mountain permafrost environments. Active rock glaciers slowly move downslope, and their kinematics is related to the internal structure and driven by external factors associated with the climatic variables. Rock glacier velocity varies on different time scales, from millennial to annual, and their movement can be observed using a range of techniques. We measured velocity variations of an active rock glacier in the eastern European Alps on an hourly time scale, by using a ground based synthetic aperture radar. For the first time, we documented a peculiar kinematic behavior for a rock glacier, showing a “step‐like” cumulative movement associated with velocity peaks occurring at a regular daily rhythm. The internal processes driving the kinematics of rock glaciers are still not fully understood, and further investigations are needed to clarify the main reasons for the pattern observed in this study. Our unique data provide a new perspective to improve understanding of rock glacier kinematics and their recent velocity acceleration driven by climate change.
Key Points
We used terrestrial radar interferometry to measure the displacement of an active rock glacier on an hourly time scale
We observed velocity peaks lasting 4–11 hr, separated by phases of stagnation lasting 13–20 hr
The velocity peaks were observed to have a regular rhythm during the investigated period
An integrated study of the litho-, bio-, and isotope stratigraphy of carbonates in the Southern Alps was undertaken in order to better constrain δ13C variations during the Late Carboniferous to Late ...Permian. The presented high resolution isotope curves are based on 1299 δ13Ccarb and 396 δ13Corg analyses. The carbon isotope record of diagenetically unaltered samples from the Carnic Alps (Austria) and Karavanke Mountains (Slovenia) shows generally high δ13C values, but Late Carboniferous and Early Permian successions are affected by a diagenetic alteration as consequence of glacio-eustatic sea level changes. Negative δ13C excursions are related to low-stand deposits and caused by diagenetic processes during subaerial exposure. The comparison with δ13C records from other parts of the world demonstrate that δ13C values are high in most unaltered samples, an overall negative trend during the Permian, as recently published, is not obvious and negative excursions related to changes in the carbon isotope composition of the global oceanic carbon pool cannot be confirmed, except for the Permian–Triassic boundary interval.
•A carbon isotope record for the Late Paleozoic of the Southern Alps is presented.•Eustatic sea-level fluctuations/subaerial exposure results in diagenetic alteration.•Negative carbon isotope excursions seen as consequence of diagenetic resetting•An overall negative trend in δ13C during the Permian is not confirmed.
Abstract Cryospheric long-term timeseries get increasingly important. To document climate-related effects on long-term viscous creep of ice-rich mountain permafrost, we investigated timeseries ...(1995–2022) of geodetically-derived Rock Glacier Velocity (RGV), i.e. spatially averaged interannual velocity timeseries related to a rock glacier (RG) unit or part of it. We considered 50 RGV from 43 RGs spatially covering the entire European Alps. Eight of these RGs are destabilized. Results show that RGV are distinctly variable ranging from 0.04 to 6.23 m a −1 . Acceleration and deceleration at many RGs are highly correlated with similar behaviour over 2.5 decades for 15 timeseries. In addition to a general long-term, warming-induced trend of increasing velocities, three main phases of distinct acceleration (2000–2004, 2008–2015, 2018–2020), interrupted by deceleration or steady state conditions, were identified. The evolution is attributed to climate forcing and underlines the significance of RGV as a product of the Essential Climate Variable (ECV) permafrost. We show that RGV data are valuable as climate indicators, but such data should always be assessed critically considering changing local factors (geomorphic, thermal, hydrologic) and monitoring approaches. To extract a climate signal, larger RGV ensembles should be analysed. Criteria for selecting new RGV-sites are proposed.
The >1,000 m-thick Carboniferous sedimentary succession of Nötsch is divided into the Erlachgraben, Badstub, and Nötsch formations with poorly constrained precise ages, but probably constituting a ...continuous lithostratigraphic Group deposited from the latest Viséan to the early Bashkirian, thus including a complete Serpukhovian succession. We date the early Serpukhovian (Steshevian) in exotic limestone clasts of the Badstub Fm. based on algae and foraminifers. These limestone clasts have been reworked from a carbonate shelf, indicating that they are older than the Badstub Fm. Microfacies and fossil assemblages indicate that a shallow marine carbonate shelf was developed at the northern margin of the deep-sea basin of Nötsch. The assemblages include the red alga Hortonella, rare green algae, and incertae sedis algae Praedonezella, Aoujgalia, and Frustulata; howchiniid and lasiodiscid foraminifers; atypical endothyrids, probably belonging to Semiendothyra emend.; rare Janischewskina; taxonomically disputable eostaffellids (including Eostaffellina aff. paraprotvae) and pseudoendothyrids; attached forms transitional between pseudolituotubid Fusulinata and calcivertellid Miliolata; and probably the oldest known free Miliolata. Newly described taxa include the incertae sedis algae Praedonezella sebbarae nov. sp. and the foraminifers Pseudoendotaxis nov. gen., Quasilituotuba serpens nov. sp., Q. pseudospiroides nov. sp., and Eoglomospiroides carnica nov. sp. Revised foraminiferal taxa include Pseudolituotubidae, Quasilituotuba cf. serpuchoviensis nov. comb., and Q. ex gr. extensa nov. comb. The studied material provides information about the phylogeny of the first Miliolata and permits the reconstruction of the lineage of Pseudolituotubidae and Calcivertellidae, between the classes Fusulinata and Miliolata. The palaeobiogeography of Austria during the Serpukhovian is not yet clearly established, but relationships with the Saharan and Mediterranean Provinces exist, and especially with the Donbass. Fewer relationships are conspicuous with England, the Moscow Basin or the Urals.
Active rock glaciers—known as mixtures of unconsolidated debris with interstitial ice, ice lenses or a core of massive ice—are widespread indicators of mountain permafrost. The age of a frozen rock ...glacier core in the Central European Alps (Lazaun, Italy) was dated to about 10,000 years. Here we report on the chemical composition of the frozen Lazaun core. The ice containing part of the core extended from about 2.8 m down to 24 m depth and consisted of two lobes—both a mix of ice and debris, separated by more than 3 m thick almost ice-free layer. The two lobes of the core showed layers of high solute content and peak values of electrical conductivity exceeding 1,000 μS/cm, but they differed in acidity and metal concentration. High acidity (minimum pH of 4.15) and high levels of elements like nickel, cobalt, zinc, manganese, iron and aluminum characterized the upper lobe, while neutral to alkaline pH and low metal values prevailed in the bottom lobe. We attributed solutes accumulated in the ice matrix to the weathering of bedrock minerals, with peak values favored by the oxidation of pyrite, or by an enhanced reactive surface area in fine-grained sediment layers. The chemical composition of the ice core also revealed signals of prehistoric atmospheric deposition from different sources including wood combustion, metal ore mining, and large volcanic eruptions (Thera, Aniakchak II). To our knowledge, this is the first study that presents the chemical stratigraphy of an entire rock glacier ice core.
Rock glaciers are widespread periglacial landforms in mountain regions like the European Alps. Depending on their ice content, they are characterized by slow downslope displacement due to permafrost ...creep. These landforms are usually mapped within inventories, but understand their activity is a very difficult task, which is frequently accomplished using geomorphological field evidences, direct measurements, or remote sensing approaches. In this work, a powerful method to analyze the rock glaciers’ activity was developed exploiting the synthetic aperture radar (SAR) satellite data. In detail, the interferometric coherence estimated from Sentinel-1 data was used as key indicator of displacement, developing an unsupervised classification method to distinguish moving (i.e., characterized by detectable displacement) from no-moving (i.e., without detectable displacement) rock glaciers. The original application of interferometric coherence, estimated here using the rock glacier outlines as boundaries instead of regular kernel windows, allows describing the activity of rock glaciers at a regional-scale. The method was developed and tested over a large mountainous area located in the Eastern European Alps (South Tyrol and western part of Trentino, Italy) and takes into account all the factors that may limit the effectiveness of the coherence in describing the rock glaciers’ activity. The activity status of more than 1600 rock glaciers was classified by our method, identifying more than 290 rock glaciers as moving. The method was validated using an independent set of rock glaciers whose activity is well-known, obtaining an accuracy of 88%. Our method is replicable over any large mountainous area where rock glaciers are already mapped and makes it possible to compensate for the drawbacks of time-consuming and subjective analysis based on geomorphological evidences or other SAR approaches.
The Late Paleozoic (early Kasimovian–late Artinskian) sedimentary sequence of the Carnic Alps (Austria/Italy) is composed of cyclic, shallow-marine, mixed siliciclastic–carbonate sedimentary rocks. ...It contains different types of skeletal mounds in different stratigraphic levels. The oldest mounds occur at the base of the Auernig Group, within a transgressive sequence of the basal Meledis Formation. These mounds are small and built by auloporid corals. Algal mounds are developed in the Auernig Formation of the Auernig Group, forming biostromes, and Lower
Pseudoschwagerina Limestone of the Rattendorf Group forming biostromes and bioherms. The dominant mound-forming organism of these mounds is the dasycladacean alga
Anthracoporella spectabilis. In mounds of the Auernig Formation subordinately the ancestral corallinacean alga
Archaeolithophyllum missouriense is present, whereas in mounds of the Lower
Pseudoschwagerina Limestone a few calcisponges and phylloid algae occur locally at the base and on top of some
Anthracoporella mounds. Mounds of the Auernig Formation formed during relative sea level highstands whereas mounds of the Lower
Pseudoschwagerina Limestone formed during transgression. The depositional environment was in the shallow marine, low-turbulence photic zone, just below the active wave base and lacking siliciclastic influx. The algal mounds of the Carnic Alps differ significantly from all other algal mounds in composition, structure, zonation and diagenesis; the formation of the mounds cannot be explained by the model proposed by Wilson (1975). The largest mounds occur in the Trogkofel Limestone, they are composed of
Tubiphytes/Archaeolithoporella boundstone, which shows some similarities to the “
Tubiphytes thickets” of stage 2 of the massive Capitan reef complex of the Guadalupe Mountains of New Mexico/West Texas.
Le Paléozoïque supérieur (Kassimovien inférieur–Artinskien supérieur) des Alpes Carniques (Autriche/Italie) est composé d’une série sédimentaire mixte siliciclastique et carbonatée, cyclique, de mer peu profonde. Cet ensemble contient différents types de bioconstructions (« skeletal mounds ») à différents niveaux. Les plus anciens monticules bioconstruits sont situés à la base du groupe d’Auernig, dans une séquence transgressive de la formation de Meledis basale. De taille modeste, ils sont édifiés par des tabulés auloporidés. Des biostromes algaires sont fréquents dans la formation d’Auernig du groupe éponyme et dans le Calcaire inférieur à
Pseudoschwagerina du groupe de Rattendorf, à la fois sous forme de biostromes et de biohermes. Le principal organisme constructeur est la dasycladale seletonellacée
Anthracoporella spectabilis. Dans la formation d’Auernig, des algues corallines ancestrales
Archaeolithophyllum missouriense leur sont subordonnées, tandis que dans le Calcaire inférieur à
Pseudoschwagerina, quelques calcisponges et de rares algues phylloïdes les accompagnent localement, à la base et au sommet de certains édifices. Les monticules de la formation d’Auernig se sont formés lors de hauts-niveaux marins relatifs, alors que ceux de l’autre formation ont pris naissance durant des transgressions. L’environnement de dépôt était situé en mer peu profonde, dans la zone photique, loin des apports siliciclastiques et en eaux faiblement agitées, juste sous la limite d’action des vagues. Les bioconstructions algaires des Alpes Carniques diffèrent nettement des autres monticules de ce type, par leur composition, leur structure, leur zonation et leur diagenèse ; leur formation ne peut donc pas être expliquée par le modèle proposé par Wilson (1975). Les plus grands monticules bioconstruits se rencontrent dans le Calcaire de Trogkofel. Ils sont composés de boundstones à
Tubiphytes/Archaeolithoporella qui ne sont pas sans rappeler les «
Tubiphytes thickets » du stade 2 du complexe récifal du Capitan dans les monts de Guadalupe (Nouveau Mexique et Texas occidental, États-Unis).
PDF
