The role of intracontinental deformation in supercontinent assembly: insights from the Ribeira Belt,Southeastern Brazil (Neoproterozoic West Gondwana)

In this study, we challenge the multiple collision model for the tectonic evolution of the Neoproterozoic Ribeira Belt in Southeastern Brazil. New U–Pb SHRIMP data reveal Palaeoproterozoic (2153 ± 15 Ma) and Cryogenian (783 ± 6 and 768 ± 8 Ma) granitic rocks in the Embu Domain, and detrital zircon data of metasedimentary units from the Embu and Costeiro domains suggest a coherent tectonic evolution for the whole Ribeira Belt. Rather than by multiple collisions, these data are best explained by a simpler tectonic model involving continent (craton)‐volcanic arc collisions in the Dom Feliciano and Brasilia belts that led to intracontinental crustal thickening of the adjacent thinned hinterland (Ribeira Belt) at ~640–610 Ma, followed by widespread post‐collisional magmatism and rift‐related sedimentation at ~600–540 Ma. We suggest that intracontinental orogeny is a relevant process during supercontinent assembly, as illustrated here by the evolution of significant parts of the Brasiliano orogen.     

Spring thermal resources for grapevine in Kőszeg (Hungary) deduced from a very long pictorial time series (1740–2009)

Since 1740 until now, the Book of Vine Branches encompasses beautiful pictorial representations of shoots and sprouts, collected every year on April 24th in the vineyards of the Hungarian town of K?szeg. A long time series (1740–2009) of sprouts phenological development coded with the BBCH scale is obtained through paintings visual inspection. Consequently, a model relating sprouts development with thermal resources accumulation is developed on the base of Wien daily air temperature series for the 1857–2009 period. Thermal resources is obtained with the Normal Heat Hours approach, a response curve method that takes into account the nonlinear response of phenological development to temperature. The model, calibrated and validated on the 1930–2009 period, shows an overestimation of thermal resources when applied to the 1857–1929, due to the more advanced phenology of that phase. Since this advance can be ascribed to genetics and management instead of more favorable thermal conditions, model outputs previous to 1930 are decreased by a constant factor. Finally, the 1740–2009 time series of grapevine spring thermal resources is obtained applying the model to the complete phenological time series. The analysis of the series highlights a first phase (1740–1780) characterized by high and stable availability of thermal resources during the 1740–1780, a second phase (1781–1820) with the lowest level of resources, a phase of intermediate availability (1821–1929) and a final present phase (1930–2009) with renewed high availability. The adopted method overcomes the lack of correlation for the post 1960 period shown by previous works.     

A New TanSat XCO_2 Global Product towards Climate Studies

The 1st Chinese carbon dioxide(CO2)monitoring satellite mission,TanSat,was launched in 2016.The 1st TanSat global map of CO2 dry-air mixing ratio(XCO2)measurements over land was released as version 1 data product with an accuracy of 2.11 ppmv(parts per million by volume).In this paper,we introduce a new(version 2)TanSat global XCO2 product that is approached by the Institute of Atmospheric Physics Carbon dioxide retrieval Algorithm for Satellite remote sensing(IAPCAS),and the European Space Agency(ESA)Climate Change Initiative plus(CCI+)TanSat XCO2 product by University of Leicester Full Physics(UoL-FP)retrieval algorithm.The correction of the measurement spectrum improves the accuracy(?0.08 ppmv)and precision(1.47 ppmv)of the new retrieval,which provides opportunity for further application in global carbon flux studies in the future.Inter-comparison between the two retrievals indicates a good agreement,with a standard deviation of 1.28 ppmv and a bias of?0.35 ppmv.     

Sr and Nd Characteristics of Brasiliano/Pan-African Granitoid Plutons of the Araçuaí Orogen, Southeastern Brazil: Tectonic Implications

Nd and Sr isotope data were obtained for three plutonic suites (595–505 Ma) and distinct young granitoid intrusions (503 Ma), from the southern part of the Neoproterozoic Araçuaí Orogen. The Sr and Nd isotopes (⁸⁷Sr/⁸⁶Sr, eNd) and TDM values from the plutons and distinct basement rocks are used to constrain the magma genesis of the granitoid plutons. These isotopic parameters, with e_Nd values ranging from −4 to −24 and T_DM ages from 1.3 to 2.8 Ga, for the granitoid suites, and −5 to −40 and 3.5 to 1.5 Ga, for the distinct Archean and Proterozoic basement complexes, suggest that the Jequitinhonha Complex metasediments are the main crustal source for most of these plutons, except for the youngest granitoid intrusions, which may have a protolith similar to the Mantiqueira and Guanhães complexes. Furthermore, the isotope data indicate a minor, but important, participation of Neoproterozoic oceanic lithosphere in the granite genesis, which corroborates with a confined orogenic model and a narrow oceanic consumption (B-subduction) for the Araçuaí Orogen.     

Upper cretaceous biostratigraphy of the south-central Pyrenees (Lleida,Spain)

Abstract

Biostratigraphical data using larger foraminifera and planktonic foraminifera permitted us to establish the correlation between shallow platform sediments rich in larger foraminifera (Montsec and Serres Marginals thrust sheets) and deeper ones containing planktonic foraminifera (Boixols thrust sheet).

Consequently, the Santa Fe limestones containing Ovalveolina-Praealveolinaassemblage represent the Cenomanian. Early Turonian ( ‘IT~ archaeocretacea and P. helvetica zones) exist in both, Montsec and Boixols thrust sheets and it is constituted by Pithonella limestones. Late Turonian (M. schneegansi zone) is only present in Boixols thrust sheet (Reguard Fm.), the Montsec thrust sheet having an erosive hiatus.

Late Coniacian-Early Santonian (D. Concavata zone) is represented in the Montsec thrust sheet (Cova Limestones) and in the eastern part of the Boixols thrust sheet (St. Corneli Fm.) by two differents facies giving two different microfaunal assemblages; the firts one, characterized by Ophtalmidiidae s.l indicate a restricted lagoonal environment while the second one, characterized by diverses species of complex agglutinated, Fabulariidae, Meandropsinidae and Rotaliidae, represents an open shallow platform. In the Boixols thrust sheet (Anseroles Fm.) dominate the planktonic foraminifera and small benthic.

In the late Santonian (D. asyrnetrica zone) the sea reached as far as Serres Marginales thrust sheet where sediments (Tragó de Noguera unit) are terrigenous and deposited in a very shallow platform. In the Montsec thrust sheet (Montsec marls) the larger foraminifera indicate a platform deeper than that of the Serres Marginals thrust sheet. In the Boixols thrust sheet the sediments are deposited in an outer platform (Herbasavina Fm.) or turbiditic basin (Mascarell Mb.).

During Campanian times the transgresion reaches the maximum. In the Serres Marginals sediments are deposited in a restricted shallow environment rich in Meandropsinidae (Serres Limestones). In the Montsec thrust sheet they are deposited in a platform with patch reefs and shoals (Terradets limestones) and in the Boixols one in an outer platform, talus and/or basin.

During Early Maastrichtian times (C. falsostuarti zone) terrigenous materials arrived in the basin, the rate of sedimentation increased outstripping the subsidence rate and the retreat of the sea to the north. Late Maastrichtian (C. gansseri zone) is only present in the Boixols thrust sheet.     

Late Neogene sequence stratigraphic evolution of the Foz do Amazonas Basin,Brazil

The margin of the Foz do Amazonas Basin saw a shift from predominantly carbonate to siliciclastic sedimentation in the early late Miocene. By this time, the Amazon shelf had also been incised by a canyon that allowed direct influx of sediment to the basin floor, thus confirming that the palaeo‐Amazon fan had already initiated by that time (9.5–8.3 Ma). Above this interval, during a prolonged lowstand, Messinian third‐order sequences are preserved only in the incised‐valley fills of the canyon with no equivalent strata on the shelf. Third‐ and fourth‐order sequences younger than Messinian are preserved on the shelf after sea‐level rise above the shelf by the early Pliocene. Sequences younger than 3.8 Ma often show fourth‐order cyclicity with an average duration of 400 ka (larger scale eccentricity cycles) often preserved in high‐sedimentation‐rate areas of river deltas. Mass wasting and transportation of slope sediments to the basin began to play an important role in sediment dispersal at least as far back as the mid‐Pliocene, after rapid progradation had produced steeper slopes more prone to failure.     

Seismological constraints on the 2018 Mt. Etna (Italy) flank eruption and implications for the flank dynamics of the volcano

3D earthquake locations, focal mechanisms and stress tensor distribution in a 16‐month interval covering the 2018 Mt. Etna flank eruption, enabled us to investigate the relationship between magma intrusion and structural response of the volcano and shed light on the dynamic processes affecting the instability of Mt. Etna. The magma intrusion likely caused tension in the flanks of the volcano, leading to significant ground deformation and redistribution of stress on the neighbouring faults at the edge of Mt. Etna's unstable sector, encouraging the ESE sliding of the eastern flank of the volcano. Accordingly, FPSs of the post‐eruptive events show strike slip faulting mechanisms, under a stress regime characterized by a maximum compressive σ₁, NE‐SW oriented. In this perspective, any flank eruption could temporarily enhance the sliding process of both the southern and eastern flanks of the volcano.     

Sea-state contributions to sea-level variability in the European Seas

Ocean Dynamics - The contribution of sea-state-induced processes to sea-level variability is investigated through ocean-wave coupled simulations. These experiments are performed with a...     

Reconstruction of the prograde PT history of high-P migmatitic paragneisses via melt-reintegration approach and thermodynamic modelling (Allochthonous Complexes,NW Iberian Massif)

The Upper Units of the allochthonous complexes of the NW Iberian Massif constitute a terrane with continental affinity. They represent the vestiges of a Cambrian magmatic arc developed in the periphery of Gondwana (West African Craton) which was involved in the Devonian Variscan collision, undergoing high-P, high-T metamorphism. This includes ultramafic rocks, high-P mafic rocks (eclogites and granulites) and high-P migmatitic paragneisses. The latter rocks show an extensive migmatization with the leucosomes oriented parallel to the regional foliation. The migmatitic paragneisses are composed of garnet, kyanite, biotite, quartz, plagioclase, K-feldspar, rutile and Ti-hematite. Thermodynamic modelling using the measured bulk composition in the NCKFMASTHO system indicates metamorphic peak conditions of ~15 kbar and ~800 to 835°C, followed by a significant cooling. The prograde evolution is assessed by means of a melt-reintegration approach, using the composition of the garnet and its inclusions. An appropriate composition of liquid is added to the measured bulk composition to emulate the pre-melting bulk composition. Modelling of this melt-reintegrated composition allows to identify a colder high-P episode below ~500°C. Zircon crystals extracted from the leucosomes show overgrowths crystallized from the partial melt at c. 389 Ma (U–Pb system). The P–T–t path proposed reveals a subduction of the peri-Gondwanan arc-derived section down to mantle depths. An isobaric heating stage occurred as a result of residence at great depths and/or inception of a transient oceanic basin at c. 395 Ma. The ensuing near-isothermal exhumation occurred due to the extension related to the inception of the basin, reaching the thermal peak shortly before c. 389 Ma. Subsequent cooling is related to the underthrusting of colder oceanic and transitional crust below the HP-HT Upper Units.     

Isotopic and hydrochemistry spatial variation of sulfate for groundwater characterization in karstic aquifers

The Sierra Gorda aquifer is one of the most extensive of southern Spain. The main groundwater discharge is produced at its northern boundary through several high‐flow springs. In this study, stable isotopes of dissolved sulfate (δ³⁴S and δ¹⁸O) and groundwater chemistry were used to determine the origin of the sulfate and to characterize the groundwater flow. We sampled the main springs, as well as other minor outlets related to perched water tables, in order to determine the different sources of SO₄^2? (e.g., dissolution of evaporites and atmospheric deposition). The substantial difference in the amount of dissolved SO₄^2? between the springs located in its northwestern part (≈25 mg/L) and those elsewhere in the northern part (≈60 mg/L) suggests zones with separate groundwater flow systems. A third group of springs, far from the northeastern boundary of the permeable outcrops, shows higher SO₄^2? content than the rest (≈125 mg/L). The isotopic range of sulfate (?0.3‰ to 14.82‰ V‐CTD) points to several sources, including dissolution of Triassic or Miocene evaporites, atmospheric deposition, and decomposition of organic material in the soil. Among these, the dissolution of Triassic gypsum—which overlies the saturated zone as a consequence of the folds and faults that deform the aquifer—is the main source of SO₄^2? (range from 12.79‰ to 14.82‰ V‐CTD). This range is typical for Triassic gypsum. The higher karstification in the western sector, together with important differences in the saturated thickness between the western and eastern sectors, would also be due to the tectonic structure and could explain the difference in SO₄^2? contents in the water. This singular arrangement may cause a higher residence time of groundwater in the eastern sector; thus, a higher contact time with Triassic evaporitic rocks is inferred. Accordingly, the stable isotopes of SO₄^2? are found to be a valuable tool for identifying areas with different flow systems in the saturated zone of karstic aquifers, as well as for evaluating aspects such as the degree of karstification .