1,721,029 research outputs found
The pre-Variscan Sequence of the Carnic Alps (Italy-Austria)
Full text linkThe Pre-Variscan Sequence of the Carnic Alps is exposed across the state border between north-east Italy and Austria. It includes Middle Ordovician to lower Pennsylvanian rocks that, although affected by both Variscan and Alpine orogenesesorogeny, preserve continuous and non-metamorphosed successionssequences. Depositional settings vary from shallow water to open marine environments. Remarkable is the presence of the largest Devonian reefs of Europe, and related deposits from back reef to fore-reef and basin. The field trip is organized as a pre-congress excursion of the 90th congress of the Italian Geological Society (Trieste, September 2021) and includes three days to visit the main localities of the central sector of the Carnic Alps, focusing on various aspects of stratigraphy, palaeontology and tectonics of the sequence
Lochkovian (Lower Devonian) conodonts from Rio Malinfier Section (Carnic Alps, Italy).
No full textConodont data from the Rio Malinfier section, located in the Cason di Lanza area (Carnic Alps, Italy) are presented. Twelve taxa belonging to eight genera (Ancyrodelloides, Dvorakia, Icriodus, Lanea, Oulodus, Ozarkodina, Pseudooneotodus and Zieglerodina) allow to state a middle Lochkovian (Lower Devonian) age for the section. The lithological boundary between the Nölbling and the La Valute formations is dated to the transitans Zone
Compositional data analysis and hydrogeochemistry of the Continental Intercalaire aquifer (northwestern Africa): A regional synthesis
No full textThe Continental Intercalaire (CI) aquifer, spanning Algeria, Tunisia, and Libya, is analyzed using piezometry, major ions, and stable isotopes (δ2H, δ18O) to track flow paths from recharge to discharge areas. A new piezometric map was generated for the CI from the interpolation of extensive datasets from the three countries (measured in 2008). A hydrochemical study was conducted on data compiled from previous investigations (n = 248 samples) and compared to new samples from this study (n = 10 samples). Hierarchical cluster analysis (HCA) and principal component analysis (PCA) were applied to hydrochemical data transformed using the centered log ratio method. The piezometric map, created using a nested model (spherical and gaussian variograms), achieved high accuracy (MAE = 0.09 m; RMSE = 26.62 m). Variography revealed the lateral continuity of the CI aquifer over ~600 km, in agreement with previous studies on flow paths and recharge characteristics. Depth to groundwater is shallowest in coastal areas (~20 m) and deepest in the Sahara (440 m). The hydrochemistry data shows that there is a progression towards the NaCl-SO4 water type along flow paths. Compositional data analysis (CoDA) successfully differentiates similar water types, providing additional insights into CI aquifer geochemistry. Isotopes proved essential in interpreting both paleo-recharge and modern-recharge compositions, considering depletion and enrichment in δ2H and δ18O compared to the global meteoric water line (GMWL) and the palaeo water line (PWL). These results are vital for sustainable water management and environmental planning
Uppermost Ordovician to lowermost Devonian conodonts from the Valentintörl section and comments on the post Hirnantian hiatus in the Carnic Alps
No full textA detailed biostratigraphic investigation has been carried out by means of conodonts in the uppermost Ordovician-lowermost Devonian sector of the Valentintörl cliff, located in the Austrian part of the Carnic Alps. Biostratigraphic data document in continuity all conodont biozones from the lowermost Ludlow to the upper Přídolí, with such a limited thickness to suggest that the Valentintörl section exposes the most condensed upper Silurian section in the Carnic Alps documented so far. A general discussion on the extension of the hiatus between Ordovician and Silurian sequences in the Carnic Alps is presented. Three new conodont species belonging to genera Cuspigrandiosa, Wurmiella and Zieglerodina are described, but left in open nomenclature awaiting more specimens to be collected
Record of a sea level drop in the lower Mississippian limestones near Passo di Monte Croce Carnico (Carnic Alps, Italy). : sea level drop in the Carboniferous of the Carnic Alps
No full textThe lower Carboniferous succession of the Carnic Alps represents the best-preserved example of such stratigraphic interval within the Alps, thus providing crucial insights for paleogeographic and paleoclimatic reconstructions. This research focuses on the combined biostratigraphic and sedimentological analyses of a stratigraphic section near Passo di Monte Croce Carnico (central Carnic Alps). The presence of two polygonal sedimentary structure-bearing levels suggests a sea-level drop. Conodont biostratigraphy places these events within the lower part of the Gnathodus interregnum, correlating with the latest Tournaisian. These data, combined with insights from coeval sedimentary records within the Carnic basin and from other basins worldwide, indicate that higher-frequency sea-level fluctuations, superimposed on an overall regressive trend, influenced the late Tournaisian evolution of the Carnic Basin
Lochkovian conodonts in the Rio Malinfier West section
Full text linkThe Lockhovian conodont fauna from the new Rio Malinfier section is discussed and commented
The “Lochkovian-Pragian Event” re-assessed: New data from the low latitude shelf of peri-Gondwana
Full text linkIn the late Lochkovian a regression is documented in several areas of the world, followed by a transgression in the early Pragian. Connected with the eustatic variation, a minor extinction event occurred (“Lochkovian-Pragian Event”), affecting several fossil groups, a strong reduction of carbonate production and sedimentary facies changes. The Carnic Alps are a key area for studying this event, because Lower Devonian rocks are widely exposed, representing diverse sedimentary environments from shallow water to relatively deep shelf. Fourteen sections were measured along the Carnic Alps across the Lochkovian-Pragian boundary. In the shallower part of the basin, both the Polinik and the Seekopf formations span the boundary, but evident erosional surfaces are observable in the field at the Lochkovian-Pragian boundary. Above the unconformity, at places the so-called megaclast horizon is present in the Seekopf Formation. In intermediate settings the Rauchkofel Fm. is unconfomably followed by the Kellerwand Fm., and different parts of the upper Lochkovian and lower Pragian are missing in the various sections. In the deeper parts of the basin the transition from the La Valute Fm. to the Findenig Fm. is slightly diachronous from the latest Lochkovian to the earliest Pragian; however, conodonts and tentaculitids are rare in the marly boundary beds, preventing a precise chronostratigraphic calibration of these levels. At places, evidence of subaerial exposure at the formational boundary is documented. In general, the hiatus seems to be larger in the western part of the Carnic Alps, in correspondence with the shallower parts of the succession, suggesting a sea level drop in the late Lochkovian, followed by a transgression in the Pragian. Data from the Carnic Alps are compared with those of other regions of North Gondwana to demonstrate that the sealevel variation at the Lochkovian-Pragian boundary are of global importance
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