It has been argued that the beginning of significant pelagic calcification could have been linked to the Carnian Pluvial Episode (CPE), a climate change in the Late Triassic (~234–232 Ma) that was ...marked by C-cycle disruption and global warming. Nevertheless, abundant calcareous nannofossils have been described so far only in post-CPE rocks, and therefore no conclusive hypotheses can be drawn on possible causal links with it. Here we show that in deep-water successions of the Western Tethys, Orthopithonella calcispheres interpreted as calcareous dinocysts became an important component of carbonate sedimentation from the onset of the CPE, and could constitute up to 8% of hemipelagic limestones. Before the CPE, in similar depositional environments, calcispheres are rare or absent, and never constitute a significant part of the sediment. This change in the deep-water carbonate sedimentation, is mirrored in the shallow water environments by the rise of the reefs built by Scleractinia corals. These important innovations in Earth's carbonate systems may indicate a deep modification in the ocean biogeochemistry during the CPE.
•Calcispheres were studied in successions across the Carnian Pluvial Episode (CPE).•In Western Tethys Calcispheres are abundant from the onset of the CPE.•They belong to the genus Orthopithonella.•They were a significant component of CPE hemipelagic–pelagic limestones.
Magmatic rocks from the Dolomites, Carnic and Julian Alps, Italy, have been sampled to investigate the origin and geodynamic setting of Triassic magmatism in the Southern Alps. Basaltic, gabbroic and ...lamprophyric samples have been characterized for their petrography, mineral chemistry, whole-rock major and trace elements, and Sr, Nd and Pb isotopic compositions. Geothermobarometric estimates suggest that the basaltic magmas crystallized mostly at depths of 14–20 km. Isotopic data show variable degrees of crustal contamination decreasing westwards, probably reflecting a progressively more restitic nature of the crust, which has been variably affected by melting during the Permian period. Geochemical and isotopic data suggest that the mantle source was metasomatized by slab-derived fluids. In agreement with previous studies and based on geological evidence, we argue that this metasomatism was not contemporaneous with the Ladinian–Carnian magmatism but was related to previous subduction episodes. The lamprophyres, which likely originated some 20 Ma later by lower degrees of melting and at higher pressures with respect to the basaltic suite, suggest that the mantle source regions of Triassic magmatism in the Dolomites was both laterally and vertically heterogeneous. We conclude that the orogenic signatures of the magmas do not imply any coeval subduction in the surrounding of Adria. We rather suggest that this magmatism is related to the Triassic rifting episodes that affected the western Mediterranean region and that were ultimately connected to the rifting events that caused the break-up of Pangea during the Late Triassic – Early Jurassic period.
High altitude karstic environments often preserve permanent ice deposits within caves, representing the lesser-known portion of the cryosphere. Despite being not so widespread and easily reachable as ...mountain glaciers and ice caps, ice caves preserve much information about past environmental changes and climatic evolution.
We selected 1111 ice caves from the existing cave inventory, predominantly but not exclusively located in the periglacial domain where permafrost is not dominant (i.e., with mean annual air temperature <3°C but not in a permafrost environment). The influence of climate and topography on ice cave distribution is also investigated. In order to assess the thickness and the inner structure of the deposits, we selected two exemplary ice caves in the Canin massif (Julian Alps) performing several multifrequency GPR surveys. A strong influence of global and local climate change in the evolution of the ice deposits has been particularly highlighted in the dynamic ice cave type, especially in regard to the role of weather extremes. The natural response of ice caves to a warming climate could lead to a fast reduction of such ice masses. The increased occurrence of weather extremes, especially warmer and more intense precipitation caused by higher mean 0°C-isotherms, could in fact be crucial in the future mass balance evolution of such permanent ice deposits.
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•Permanent ice deposits in high altitude karstic environment•Inventory of ice caves in the Southeastern European Alps•The role of weather extremes under climate change in the evolution of ice caves•Relation between ice caves distribution and the climate•The use of GPR in imaging and characterization of the underground cryosphere
This article describes the flora of the northern slopes of the Triglav Peak (Julian Alps). Further, we discuss the flora of Dubrovnik (the old town area) and the flora of the towns of Budva and ...Podgoritsa.
Sieve lobes typically appear in gravel‐rich and matrix‐poor alluvial fans. Despite being extensively studied, the sieve‐lobe facies has been defined largely based on qualitative field observations ...without quantitative sedimentological analyses. Additionally, depositional activity of sieve lobes has not been monitored over extended periods (monthly to annually) and not directly associated with specific precipitation triggers. Furthermore, the internal geometry of sieve‐lobe built alluvial fans has not yet been imaged by subsurface methods. We performed a multi‐method analysis of sieve lobes in the Julian Alps (NW Slovenia) on an alpine alluvial fan composed of carbonate gravels. We performed a detailed textural and structural sedimentological analysis of 11 recent sieve lobes differing in size and age. A three‐year aerial survey of the alluvial fan surface with a small unmanned aircraft and photogrammetric modelling was used to detect active sieve‐lobe evolution. Detected sieve‐lobe formation events and volumetric surface changes were paired with triggering precipitation events. Ground‐penetrating radar (GPR) profiling depicted the geometry of the sieve‐lobe built alluvial fan. The sieve‐lobe facies consists of over 80% poorly sorted, open‐framework gravels and less than 2% mud. Lobes exhibit downward coarsening and increase in clast mean size. These textural and structural characteristics are present in all sieve lobes regardless of their age and size. Sieve lobes form with a sub‐annual frequency, usually following 24 h rainfall events exceeding 50 mm. Over 1000 m3 of sediment was deposited during these events. The GPR profiles confirm that the studied alluvial fan is formed predominantly by stacked sieve lobes. Quantitative sedimentary analysis of sieve lobes, monitoring of their recent evolution, and depiction of their subsurface geometry—demonstrated in this study—reinforce the challenged concept that sieve lobes are one of the main building blocks of alluvial fans. This work also demonstrates that, under specific conditions, sieving may become the dominant alluvial fan‐forming process.
We performed a detailed sedimentological analysis of 11 sieve lobes on an active alluvial fan. A three‐year aerial surface survey detected active sieve‐lobe evolution, which was paired with triggering precipitation events. Ground‐penetrating radar depicted the architecture of the sieve‐lobe built alluvial fan. Lobes exhibit downward coarsening and increased clast mean size. They are deposited annually during rainfalls exceeding 50 mm, during which more than 1000 m3 of sediment was deposited. Gravel‐rich and matrix‐poor alluvial fans can be almost entirely sieve‐lobe built.
Sequences of lake sediments often form long and continuous records that may be sensitive recorders of seismic shaking. A multi‐proxy analysis of Lake Bohinj sediments associated with a ...well‐constrained chronology was conducted to reconstruct Holocene seismic activity in the Julian Alps (Slovenia). A seismic reflection survey and sedimentological analyses identified 29 homogenite‐type deposits related to mass‐wasting deposits. The most recent homogenites can be linked to historical regional earthquakes (i.e. 1348 ad, 1511 ad and 1690 ad) with strong epicentral intensity greater than ‘damaging’ (VIII) on the Medvedev–Sponheuer–Karnik scale. The correlation between the historical earthquake data set and the homogenites identified in a core isolated from local stream inputs, allows interpretation of all similar deposits as earthquake related. This work extends the earthquake chronicle of the last 6600 years in this area with a total of 29 events recorded. The early Holocene sedimentary record is disturbed by a seismic event (6617 ± 94 cal yr bp) that reworked previously deposited sediment and led to a thick sediment deposit identified in the seismic survey. The period between 3500 cal yr bp and 2000 cal yr bp is characterized by a major destabilization in the watershed by human activities that led to increases in erosion and sedimentation rates. This change increased the lake's sensitivity to recording an earthquake (earthquake‐sensitivity threshold index) with the occurrence of 72 turbidite‐type deposits over this period. The high turbidite frequency identified could be the consequence of this change in lake earthquake sensitivity and thus these turbidites could be triggered by earthquake shaking, as other origins are discarded. This study illustrates why it is not acceptable to propose a return period for seismic activity recorded in lake sediment if the sedimentation rate varies significantly.
Mountain grazing and ore processing had a significant impact on the Alpine environment in the last 5000 years, but few studies have so far focused on environmental changes of the south eastern Alps. ...This study investigates the vegetation history and sedimentary processes in the catchment of Lake Bohinj (Julian Alps, Slovenia), where a 12-m-long core was collected in the central part of the lake. Sediment in the early Holocene section of the core was partially reworked due to a major seismic event dated to 6711–6523 yr cal BP (Rapuc et al. 2018), therefore a detailed palaeoenvironmental reconstruction was performed only for the top 4.4 m of the core. Here the results of mineralogical, sedimentological, geochemical, stable isotope (δ13C and δ15N), and pollen analysis are presented in order to better understand the impact of people (agriculture, grazing, mining) on the environment, and climate-human interactions over the last 6600 years.
The results of palynological research suggest that at ca. 6000 yr cal BP Lake Bohinj was surrounded by mixed forest composed of Picea, Abies, deciduous Quercus, with Fagus becoming dominant after ca. 3300 yr cal BP. In the Bronze and especially the Iron Age (3500–2500 yr cal BP), when the region was, according to archaeological data, densely populated, clearing of forests due to agriculture, livestock production and metallurgical activities was detected through Cerealia type pollen, Plantago lanceolata, and the decline of Abies. These activities probably triggered soil erosion recorded as increased sedimentation rates. In the subsequent centuries human impact on the environment continued (increased), but it seems that the watershed was not destabilised again. Several periods of high terrigenous input were recorded at 6100–6000, 5700–5550, 5000–4600, 3900, 3700–3550, 2300–2200 yr cal BP and could be associated with a mobilisation of river inflow from the eastern flysch bearing catchment, due to river migration during periods of wetter climate. These flood patterns match with periods of enhanced flood activity in the wider Alpine region.
•Vegetation history and sedimentary processes at Lake Bohinj were investigated.•Several periods of wetter climate were recorded in the last 6600 years.•Human impact (grazing and fire disturbance) intensified in the Bronze Age.•In the Iron Age (2600 BP) human activity triggered massive soil erosion.
Small mountain lakes are natural archives for understanding long‐term natural and anthropogenic impact on the environment. This study focused on long‐term (last ca. 13 000 years) vegetation changes ...and sedimentary processes in the catchment area of Lake Planina pri jezeru (1430 m a.s.l.) by using mineralogical, geochemical and palynological methods. Palynological results suggest that regional vegetation between 12 900 and 11 700 cal a bp was a herbaceous–forest tundra (Pinus, Artemisia, Poaceae). Climate warming at the beginning of the Holocene (ca. 11 700 cal a bp) caused the transition from a wetland (Cyperaceae) to an eutrophic lake with alternating anoxic (pyrite) and oxic conditions (gypsum). In addition, the surrounding area became forested (Picea, Larix, Ulmus). Fagus expanded at 10 200 cal a bp and Abies at 8200 cal a bp. Between 7500 and 4300 cal a bp, human impact on the environment was barely noticeable and mostly limited to grazing. During 4300–430 cal a bp human impact became more evident and gradually increased. The greatest influence was observed from 430 cal a bp onwards, when excessive exploitation of the surrounding area (logging and grazing) severely eutrophicated the lake.
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