Tonsteins, predominantly solid kaolinite clay interbeds, are widespread in the coals of the Kuzne... more Tonsteins, predominantly solid kaolinite clay interbeds, are widespread in the coals of the Kuznetsk Basin and usually contain idiomorphic zircon grains of magmatic origin in quantities suitable for uranium-lead (U-Pb) radiometric dating. For the first time, tonstein zircons from coal seam 78 of the Tailugan Formation (Fm) are dated by two methods: Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and Chemical Abrasion Isotope-Dilution Thermal Ionization Mass Spectrometry (CA-ID-TIMS). The CA-ID-TIMS datings of 257.0 ± 1.3 Ma and 256.6 ± 0.4 Ma determine the age of the lower boundary of the Tailugan Fm and the Tailuganian Regional Stage at 257.0 Ma. We estimate the duration of the Tailuganian to be around 4.22 million years. The dating results make it possible to directly correlate the Tailuganian of the Kuzbass with the upper half of the Wuchiapingian and with most of the Changhsingian of the International Chronostratigraphic Scale. The accumulation rate of to...
The end-Permian mass extinction, the largest biological crisis in Earth history, is currently und... more The end-Permian mass extinction, the largest biological crisis in Earth history, is currently understood in the context of Siberian Traps volcanism introducing large quantities of greenhouse gases to the atmosphere, culminating in the Early Triassic hothouse. In our study, the late Permian and Early Triassic atmospheric CO2 history was reconstructed by applying the paleosol pCO2 barometer. Atmospheric pCO2 shows an approximate 4× increase from mean concentrations of 412–919 ppmv in the late Permian (Changhsingian) to maximum levels between 2181 and 2610 ppmv in the Early Triassic (late Griesbachian). Mean CO2 estimates for the later Early Triassic are between 1261–1936 ppmv (Dienerian) and 1063–1757 ppmv (Spathian). Significantly lower concentrations ranging from 343 to 634 ppmv are reconstructed for the latest Early to Middle Triassic (Anisian). The 5 m.y. episode of elevated pCO2 suggests that negative feedback mechanisms such as silicate weathering were not effective enough to re...
Another situation is observed in the Vaga fluvial system. We identified the well-expressed grayis... more Another situation is observed in the Vaga fluvial system. We identified the well-expressed grayish varved clays within the valleys of Vaga and its tributaries Kuloi and Kokshen’ga. The maximum (10 m) thickness of varved clays was observed in the outcrop near the Kuloi-Vaga confluence; thickness of sand and silt layers varies significantly, from several mm to several tens of cm, that means the unstable hydrodynamic regime, with alteration of lacustrine and fluvial sedimentary environment. At the top of the lacustrine unit there are water-escape structures characteristic for the proglacial lake deposits. Upstream the thickness of varved clay layer decreases and then recedes completely. The limit of varved clay deposits goes form SW to NE from Vaga to Kokshen’ga rivers. Therefore, we can identify one episode of proglacial lake formation in the Late Pleistocene within the Severnaya Dvina catchment area. Two separate lake systems formed during the LGM (~ca 20 kyr BP): the Severnaya Dvina...
RIVISTA ITALIANA DI PALEONTOLOGIA E STRATIGRAFIA, 2022
Non-marine bivalves are key fossils in Permian continental stratigraphy and palaeogeography. Alth... more Non-marine bivalves are key fossils in Permian continental stratigraphy and palaeogeography. Although known since the end of 19th century, the occurrences from the continental basins of the Southern Alps have never been extensively studied. The non-marine bivalves from the Lower Permian Collio Formation (Brescian pre-Alps) are herein revised, and those from the Guncina Formation (Athesian District) are described for the first time. These two units yielded non-marine bivalves belonging to the genus Palaeomutela sensu lato, which is widespread in the Permian continental successions of eastern Euramerica. Three Palaeomutela morphotypes have been herein described: oval-subtriangular, subtrapezoidal and elongated. The latter includes several specimens herein assigned to Palaeomutela (Palaeanodonta) berrutii sp. nov. and dominates the Collio Formation association. The Guncina Formation yielded also the genus Redikorella, for the first time co-occurring on the same stratigraphic horizon of...
Tonsteins, predominantly solid kaolinite clay interbeds, are widespread in the coals of the Kuzne... more Tonsteins, predominantly solid kaolinite clay interbeds, are widespread in the coals of the Kuznetsk Basin and usually contain idiomorphic zircon grains of magmatic origin in quantities suitable for uranium-lead (U-Pb) radiometric dating. For the first time, tonstein zircons from coal seam 78 of the Tailugan Formation (Fm) are dated by two methods: Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and Chemical Abrasion Isotope-Dilution Thermal Ionization Mass Spectrometry (CA-ID-TIMS). The CA-ID-TIMS datings of 257.0 ± 1.3 Ma and 256.6 ± 0.4 Ma determine the age of the lower boundary of the Tailugan Fm and the Tailuganian Regional Stage at 257.0 Ma. We estimate the duration of the Tailuganian to be around 4.22 million years. The dating results make it possible to directly correlate the Tailuganian of the Kuzbass with the upper half of the Wuchiapingian and with most of the Changhsingian of the International Chronostratigraphic Scale. The accumulation rate of to...
The end-Permian mass extinction, the largest biological crisis in Earth history, is currently und... more The end-Permian mass extinction, the largest biological crisis in Earth history, is currently understood in the context of Siberian Traps volcanism introducing large quantities of greenhouse gases to the atmosphere, culminating in the Early Triassic hothouse. In our study, the late Permian and Early Triassic atmospheric CO2 history was reconstructed by applying the paleosol pCO2 barometer. Atmospheric pCO2 shows an approximate 4× increase from mean concentrations of 412–919 ppmv in the late Permian (Changhsingian) to maximum levels between 2181 and 2610 ppmv in the Early Triassic (late Griesbachian). Mean CO2 estimates for the later Early Triassic are between 1261–1936 ppmv (Dienerian) and 1063–1757 ppmv (Spathian). Significantly lower concentrations ranging from 343 to 634 ppmv are reconstructed for the latest Early to Middle Triassic (Anisian). The 5 m.y. episode of elevated pCO2 suggests that negative feedback mechanisms such as silicate weathering were not effective enough to re...
Another situation is observed in the Vaga fluvial system. We identified the well-expressed grayis... more Another situation is observed in the Vaga fluvial system. We identified the well-expressed grayish varved clays within the valleys of Vaga and its tributaries Kuloi and Kokshen’ga. The maximum (10 m) thickness of varved clays was observed in the outcrop near the Kuloi-Vaga confluence; thickness of sand and silt layers varies significantly, from several mm to several tens of cm, that means the unstable hydrodynamic regime, with alteration of lacustrine and fluvial sedimentary environment. At the top of the lacustrine unit there are water-escape structures characteristic for the proglacial lake deposits. Upstream the thickness of varved clay layer decreases and then recedes completely. The limit of varved clay deposits goes form SW to NE from Vaga to Kokshen’ga rivers. Therefore, we can identify one episode of proglacial lake formation in the Late Pleistocene within the Severnaya Dvina catchment area. Two separate lake systems formed during the LGM (~ca 20 kyr BP): the Severnaya Dvina...
RIVISTA ITALIANA DI PALEONTOLOGIA E STRATIGRAFIA, 2022
Non-marine bivalves are key fossils in Permian continental stratigraphy and palaeogeography. Alth... more Non-marine bivalves are key fossils in Permian continental stratigraphy and palaeogeography. Although known since the end of 19th century, the occurrences from the continental basins of the Southern Alps have never been extensively studied. The non-marine bivalves from the Lower Permian Collio Formation (Brescian pre-Alps) are herein revised, and those from the Guncina Formation (Athesian District) are described for the first time. These two units yielded non-marine bivalves belonging to the genus Palaeomutela sensu lato, which is widespread in the Permian continental successions of eastern Euramerica. Three Palaeomutela morphotypes have been herein described: oval-subtriangular, subtrapezoidal and elongated. The latter includes several specimens herein assigned to Palaeomutela (Palaeanodonta) berrutii sp. nov. and dominates the Collio Formation association. The Guncina Formation yielded also the genus Redikorella, for the first time co-occurring on the same stratigraphic horizon of...
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