Intense Events Research Articles

Accretionary and collisional processes of the Brasiliano Orogeny recorded by the Tonian La Tuna ophiolite, Dom Feliciano Belt, Uruguay

Accretionary to collisional orogenies such as the Brasiliano Orogeny of eastern South America present the opportunity to distinguish between oceanic-continental (accretionary) and continental (collisional) processes. However, the multitude of geotectonic processes involved and the reduced degree of preservation of the accretionary stage restrain the interpretation of evidence. This study focuses on a metasomatite associated with the La Tuna Ophiolite in the southern Dom Feliciano Belt of the Uruguayan Shield, as these can provide crucial insights into the accretionary stage of the Brasiliano Orogeny. The metasomatite occurs as a meter-sized massive tourmalinite body surrounded by a meter-wide chloritite lens, both enclosed by the La Tuna serpentinite. Our SEM-EDS and EPMA data revealed that the serpentines from the La Tuna ophiolite are antigorite and lizardite, while chlorite was identified as clinochlore. Abundant inclusions of sheridanite chlorite in dravite tourmaline suggests that tourmaline overgrew chlorite. Dravite crystals revealed the presence of three diffuse zones with minor compositional variations, mainly enrichments in Ca and Fe towards the rims. The U-Pb LA-ICP-MS dating of metasomatic zircon yielded ages of 743.2 ± 3.4 Ma (n = 22) for the chloritite and 743.1 ± 2.4 Ma (n = 31) for the tourmalinite. High δ11B values (+12.1‰ to + 18.1‰) of tourmaline (LA-ICP-MS) suggest that the metasomatic event was caused by seawater-derived fluids in a fluid-dominated environment. The single metasomatic U-Pb age combined with the high δ11B values suggest that the metasomatites underwent more intense metasomatic events than those associated with the Bossoroca (−8.5‰ to +1.8‰) and the Ibaré ophiolites (+3.2‰ to +5.2‰) further north in the São Gabriel Terrane of the Dom Feliciano Belt. Nonetheless, a few spots in tourmaline located within fracture zones and in contact with chlorite displayed negative (c. −5‰) and low positive δ11B values (c. 2‰). These are interpreted as overprinting by crustal fluids, either during the tectonic emplacement of the La Tuna Ophiolite or during exhumation. The calculated TDM Hf model ages for zircon in tourmalinite and chloritite range from 0.74 to 1.09 Ga and their ɛHf(T) values range from +4.9 to +11.2, indicating derivation from depleted mantle sources. The data corroborate earlier results indicating that the associated La Tuna amphibolites have composition similar to N-MORB. Furthermore, the trace element composition of zircon in the metasomatites is consistent with an oceanic environment (U/Yb < 0.1). Geotectonically, the La Tuna metasomatites formed at 743 ± 2 Ma in an oceanic setting, most likely in a juvenile Adamastor Ocean basin. During the collisional stage of the Brasiliano Orogeny, the La Tuna Ophiolite was tectonically emplaced within the <666 Ma La Micaela Schist of the Paso del Drágon Complex. As such, this study on the La Tuna Ophiolite contributes direct evidence on the oceanic evolution leading up to the accretionary stage of the Brasiliano Orogeny and provides new constraints on the transition towards the collisional stage.

Impact of a Short‐Pulse High‐Intense Proton Irradiation on High‐Performance Perovskite Solar Cells

AbstractThis work investigates the radiation resistance of high‐performance multi‐component perovskite solar cells (PSCs) for the first time under extreme short‐pulse proton irradiation conditions. The devices are subjected to high‐intensity 170 keV pulsed (150 ns) proton irradiation, with a fluence of up to 1013 p cm−2, corresponding to ≈30 years of operation at low Earth orbit. A complex material characterization of the perovskite active layer and device physics analysis of the PSCs before and after short‐pulse proton irradiation is conducted. The obtained results indicate that the photovoltaic performance of the solar cells experiences a slight deterioration up to 20 % and 50 % following the low 2 × 1012 p cm−2 and high 1 × 1013 p cm−2 proton fluences, respectively, due to increased non‐radiative recombination losses. The findings reveal that multi‐component PSCs are immune even to extreme high‐intense short‐pulse proton irradiation, which exceeds harsh space conditions, including intense coronal ejection events usually associated with solar flares.

The effect of extreme rainfall on corporate financing policies

In recent years, a series of intense precipitation events has drawn public attention to the issue of extreme rainfall. This study examines the impact of precipitation anomalies on corporate financing policies and reveals that firms tend to increase their utilization of long-term debt (while decreasing their reliance on short-term debt), enhance cash reserves, and reduce cash dividend payouts in response to heightened occurrences of extreme rainfall. We provide empirical evidence indicating that such weather events can have adverse effects on firms' operational activities. The influence of extreme precipitation is particularly pronounced in sectors sensitive to rainfall, firms with geographically concentrated factories, non-state-owned enterprises, and those located in cities with limited financial institutions. Overall, this research demonstrates that firms are inclined to adjust their financing policies in response to extreme rainfall events, underscoring the significance of financial resilience in managing climate risks and shedding light on firms' financing decisions.

Attributing Venice Acqua Alta events to a changing climate and evaluating the efficacy of MoSE adaptation strategy

We use analogues of atmospheric patterns to investigate changes in four devastating Acqua Alta (flooding) events in the lagoon of Venice associated with intense Mediterranean cyclones occurred in 1966, 2008, 2018 and 2019. Our results provide evidence that changes in atmospheric circulation, although not necessarily only anthropogenically driven, are linked to the severity of these events. We also evaluate the cost and benefit of the MoSE system, which was designed to protect against flooding. Our analysis shows that the MoSE has already provided protection against analogues of the most extreme event, which occurred in 1966. These findings have significant implications for the future of Venice and other coastal cities facing similar challenges from rising sea levels due to extreme events. This study also provides a pathway to evaluate the effectiveness of adaptation in a scenario more frequent and intense extreme events if higher global warming levels will be reached.

Social anxiety and emotion regulation flexibility: a daily diary approach

ABSTRACT Previous research suggests that social anxiety symptoms are maintained and intensified by inflexible emotion regulation (ER). Therefore, we examined whether trait-level social anxiety moderates ER flexibility operationalised at both between-person (covariation between variability in emotional intensity and variability in strategy use across occasions) and within-person (associations between emotional intensity and strategy use on a given day) levels. In a sample of healthy college-aged adults (N = 185, M age = 21.89), we examined overall and emotion-specific intensities (shame, guilt, anxiety, anger, sadness) and regulatory strategies (i.e. experiential avoidance, expressive suppression, and rumination) in response to each day’s most emotionally intense event over 6 days. During the study period, we found a positive association between variability in emotional intensity and variability of experiential avoidance in individuals with lower, rather than higher, levels of trait social anxiety after controlling for key covariates (i.e. gender, personality traits, and stress exposure). However, we did not find evidence for the moderating role of trait social anxiety in ER flexibility assessed at within-person levels. Our findings highlight the need to delineate dynamic ER flexibility across everyday events.

On the phenology of coastal upwelling off central-southern Chile

Coastal upwelling is the dominant physical process triggering high biological productivity in Eastern Boundary Upwelling Systems (EBUS). These regions are characterized by intense upwelling events driven by Equatorward alongshore winds. In the Humboldt current system off central-southern Chile (30–40°S) the coastal upwelling process has been studied from several approaches including biogeochemical, fisheries and physical studies. Yet, the phenology of wind-driven upwelling along the meridional gradient has been poorly inspected. Using reanalysis data from the ERA5 product (1966–2020), we calculated the Cumulative Upwelling Index (CUI, m2 s−1 × 1000 m) to characterize the phenology of coastal upwelling off central-southern Chile, identifying the beginning (STI), the maximum (MAX) and the end (END) of the upwelling season. In addition, we quantified the duration (LUSI) and the total magnitude (TUMI) of the upwelling season. The response of the water column to cumulative wind stress was determined using in situ hydrographic data (2002–2020) from a middle shelf station off Concepción, which showed marked seasonal and interannual variability. In general, the onset, duration, and intensity of Ekman transport were highly variable. At 36.5°S (off Concepción), the STI occurred on August 6 ± 25.4 days and the duration of the upwelling season (LUSI) was ∼9 months ± 32.5 days. On the other hand, the TUMI at this latitude was −1.97 × 108± 4.88 × 107. The CUI climatology during El Niño years showed weak and late upwelling (STI = August 29 ± 16.2 days) while upwelling was strong and early (STI = July 13 ± 30.6 days) during La Niña compared to the mean climatology. The water column showed a direct response to cumulative wind-driven upwelling conditions during El Niño 2015-2016 and La Niña 2007-2008. The rise of cold (≤11 °C), saline (34.5 isohaline), dense (>25.8 kg m−3), and oxygen-poor (≤ 1 ml L−1) subsurface waters corresponded to stronger upwelling winds during La Niña 2007–2008. In contrast, coastal upwelling was substantially weak, with a warmer water column and the isotherm of 11.5 °C located below 30 m depth during El Niño 2015–2016.

#DeOlhoNosCorais: a polygonal annotated dataset to optimize coral monitoring.

Corals are colonial animals within the Phylum Cnidaria that form coral reefs, playing a significant role in marine environments by providing habitat for fish, mollusks, crustaceans, sponges, algae, and other organisms. Global climate changes are causing more intense and frequent thermal stress events, leading to corals losing their color due to the disruption of a symbiotic relationship with photosynthetic endosymbionts. Given the importance of corals to the marine environment, monitoring coral reefs is critical to understanding their response to anthropogenic impacts. Most coral monitoring activities involve underwater photographs, which can be costly to generate on large spatial scales and require processing and analysis that may be time-consuming. The Marine Ecology Laboratory (LECOM) at the Federal University of Rio Grande do Norte (UFRN) developed the project "#DeOlhoNosCorais" which encourages users to post photos of coral reefs on their social media (Instagram) using this hashtag, enabling people without previous scientific training to contribute to coral monitoring. The laboratory team identifies the species and gathers information on coral health along the Brazilian coast by analyzing each picture posted on social media. To optimize this process, we conducted baseline experiments for image classification and semantic segmentation. We analyzed the classification results of three different machine learning models using the Local Interpretable Model-agnostic Explanations (LIME) algorithm. The best results were achieved by combining EfficientNet for feature extraction and Logistic Regression for classification. Regarding semantic segmentation, the U-Net Pix2Pix model produced a pixel-level accuracy of 86%. Our results indicate that this tool can enhance image selection for coral monitoring purposes and open several perspectives for improving classification performance. Furthermore, our findings can be expanded by incorporating other datasets to create a tool that streamlines the time and cost associated with analyzing coral reef images across various regions.

Exploring recharge mechanisms of soil water in the thick unsaturated zone using water isotopes in the North China Plain

Exploring the groundwater recharge mechanisms in regions with thick unsaturated zones can enhance our understanding of intricate groundwater processes, especially in intensive agricultural regions such as the North China Plain (NCP). For example, to better answer the question of how deep soil water can be recharged, it is of utmost importance to illustrate the recharge mechanisms of groundwater under different land use types in the NCP. This study collected soil samples from four boreholes up to 18 m deep covering farmland and orchards with different stand ages and measured soil water content (SWC), stable and radioactive isotopes (δ18O, δ2H and 3H) of both soil water and groundwater. Results indicated that the movement of water through the deep vadose zone of soils was primarily piston flow based on a soil tritium profile. The infiltration rate was estimated to be 32.2 mm yr−1 based on the tritium peak method. The variations of soil water δ18O and line control excess (lc-excess) indicated that the orchards had lower evaporation effects and a higher precipitation offset than those in farmland soils. Furthermore, the deep soil water was replenished by intensive precipitation events (from July to September). The great soil water deficit and decreased deep drainage under pear orchards is usually closely related to huge water consumption by evapotranspiration (ET) via root uptake, which explains the increase of ET in pear orchards with increasing stand age. These findings have provided substantial insights into groundwater resource management in similar regions with limited water resources and recharge modeling for regions covered with thick unsaturated zones.

Emotion regulation in daily life in early psychosis: The role of contextual appraisals.

Little is known about whether and how contextual appraisals relate to emotion regulation (ER) strategy use across the ultra-high risk and first episode stages of psychosis. The present study extends previous research by investigating the extent to which different appraisal dimensions of the most negative and positive events of the day are associated with ER strategy use in individuals with ultra-high risk (UHR) and first-episode psychosis (FEP). Sixty-eight UHR individuals and fifty-five FEP individuals filled out an experience sampling evening questionnaire for six consecutive days, in which their appraisal of intensity, importance and perceived control concerning the most negative or positive event of the day, and the ER strategies they deploy in response to these events were measured. Multilevel mixed effect models showed that intensity appraisal was most closely associated with ER strategy use, as opposed to importance and controllability appraisals. Higher intense negative events were associated with more rumination and social sharing, while less intense negative events were associated with more reappraisal. Higher intense positive events were associated with a greater number of deployed strategies and more efforts in using savoring, expression and social sharing. The UHR and FEP individuals did not significantly differ regarding effects of above-mentioned appraisal dimensions on ER. These results provide evidence supporting ER flexibility in early psychosis, and event intensity emerged as the dimension most strongly associated with ER. Future research should better account for other situational factors (such as social context) that might affect ER use in psychosis.

Variability of Ionosphere Over Indian Longitudes to a Variety of Space Weather Events During December 2006

AbstractThis paper highlights the impact of intense solar events over India during 3–20 December 2006. Ionospheric effects of a major solar flare (X9) on December 5 (10:35 UT) have been investigated by using dayside and nightside magnetometer data, dayside ionosondes, and dayside GPS vTEC observations. On the next day, a stream of fast solar wind hits the magnetosphere, causing a HILDCAA (High Intensity Long Duration Continuous Auroral Activity) preceded by moderate geomagnetic storm. The origin and characteristics of a positive ionospheric storm which occurred over Tirunelveli (TIR, geomagnetic latitude: −0.18°N) in the recovery phase of storm due to simultaneous presence of enhanced O/N2 and WEJ or weakened EEJ during the HILDCAA (7th and 8th of December) is investigated. Subsequently, on December 14, the most powerful CME since the Halloween event impacts the Earth, and three SSCs are recorded on December 14, 16, and 18. The variability of the ionosphere over the Indian longitude sector due to these intense space weather fluctuations is presented by utilizing the magnetometers, ionosonde, GPS vTEC, and satellite‐based observations in the same region. This study reports the influence of prompt penetration of the magnetospheric convection electric field and the disturbance dynamo on several key ionospheric and magnetic parameters within the Indian longitude sector.

The impact of global navigation satellite system (GNSS) zenith total delay data assimilation on the short-term precipitable water vapor and precipitation forecast over Italy using the Weather Research and Forecasting (WRF) model

Abstract. The impact of assimilating GNSS-ZTD (global navigation satellite system–zenith total delay) on the precipitable water vapor and precipitation forecast over Italy is studied for the month of October 2019, which was characterized by several moderate to intense precipitation events, especially over northwestern Italy. The WRF (Weather Research and Forecasting) model, version 4.1.3, is used with its 3D-Var data assimilation system to assimilate ZTD observations from 388 GNSS receivers distributed over the country. The dataset was built collecting data from all the major national and regional GNSS permanent networks, achieving dense coverage over the whole area. The water vapor forecast is verified for the forecast hours of 1–6 h after the last data assimilation time. Results show that WRF underestimates the atmospheric water vapor content for the period, and GNSS-ZTD data assimilation improves this underestimation. The precipitation forecast is verified in the phases of 0–3 and 3–6 h after the last data assimilation time using more than 3000 rain gauges spread over Italy. The application of GNSS-ZTD data assimilation to a case study improved the precipitation forecast by increasing the rainfall maximum and by better focusing the precipitation pattern over northeastern Italy, with the main drawback being the prediction of false alarms. Considering the study over the whole period, GNSS-ZTD data assimilation had a positive impact on rainfall forecast, with an improvement in the performance up to 6 h and with statistically significant results for moderate to intense rainfall thresholds (25–30 mm (3 h)−1).

Nitrogen availability affects the responses of marsh grass and sedge plants (Phragmites australis and Bolboschoenus planiculmis) to flooding time

Flooding time and external nitrogen (N) input have been projected to be the main threats to marsh ecosystems in the scenario of more intense flooding events and N deposition. How flooding and N addition experienced at different growth stages interact in determining phenotypic change remains scarce. We established a controlled experiment (3 flooding time treatments x 5 N addition levels) using two herbaceous marsh species (Phragmites australis and Bolboschoenus planiculmis) to assess the responses of six key traits to environmental changes and the indication of plant performance. Early flooding reduced plant height and aboveground biomass of P. australis and below/aboveground biomass ratio of B. planiculmis and increased below/aboveground biomass ratio of P. australis and root biomass of B. planiculmis, whereas late flooding reduced root biomass of P. australis and ramet number and aboveground biomass of B. planiculmis. The combination of flooding and high N (16 and 32 g N m−2) exerted negative effects on ramet number of both plant species. The interaction of early flooding and low-medium N (8 and 16 g N m−2) inhibited clonal/belowground biomass ratio of both plant species. The combination of early flooding and low N (0, 4 and 8 g N m−2) promoted root biomass and below/aboveground biomass ratio of P. australis. Ramet number, plant height, and root biomass explained 80–90 % of aboveground biomass variation of both plant species, and the contribution of ramet number was greater than that of the other two traits. These results highlight that the influence of flooding time and external N input on the performance of marsh plants depends on species identity. Meanwhile, the ramet number-plant height-root biomass (RHR) strategy is supposed to be the adaptation strategy of wetland clonal plants to environmental changes, and clonal reproductive traits should be incorporated into vegetation dynamics models for marsh plants.

New Ways in Municipal Flood Mitigation: a Mixed-Integer Programming Approach and its Practical Application

Adapting to the consequences of climate change is one of the central challenges faced by humanity in the next decades. One of these consequences are intense heavy rain events, which can cause severe damage to buildings due to flooding. In this paper, we present the first use of optimization techniques that scales well enough to be applicable for supporting decision-making in planning precautionary measures for flash floods caused by heavy rain events in realistic scenarios. Our mixed-integer programming model has been implemented as an innovative decision support tool in the form of a web application, which has already been used by more than 30 engineering offices, municipalities, universities, and other institutions. The model aims to minimize the damage caused in the case of a heavy rain event by taking best-possible actions subject to a limited budget and constraints on the cooperation of residents. We further present an efficient, graph-based representation and preprocessing of the surface terrain, a combinatorial algorithm for computing an initial solution of the mixed-integer program, and computational results obtained on real-word data from different municipalities.

Evaluation of overwash vulnerability and shoreline dynamics in cyclone-prone Sagar Island, Sundarbans (India)

Situated in the climatically vulnerable Sundarbans region, Sagar Island has increasingly been subjected to intense cyclonic events, including Yaas, Amphan, Bulbul, and Aila, leading to significant alterations in its coastal morphology. This study aims to elucidate the overwash vulnerability and shoreline dynamics in Sagar Island, spanning the period from 2000 to 2020. Utilizing satellite imagery, the study employs three indices—Overwash Shoreline Ratio (OSR), Maximum Overwash Intrusion Recurrence (MOIR), and Complete Barrier Overwash (CBO)—to assess overwash vulnerability. These indices collectively indicate a heightened susceptibility to overwash intrusion, with a particular focus on the years following severe cyclonic events. Additionally, shoreline change dynamics were quantitatively analyzed using the Digital Shoreline Analysis System (DSAS) tool, revealing a strong positive correlation between shoreline recession and climatic variables. Interlinkages between overwash vulnerability and shoreline dynamics were established, confirming that both phenomena are exacerbated by climate change and extreme weather events. The study's findings have critical implications for a broad range of sectors such as agriculture, fisheries, transportation, and ecosystem conservation. The research underscores the urgency for an integrated coastal management strategy that considers both overwash vulnerability and shoreline change dynamics to enhance sustainability and resilience. This study contributes to the global discourse on coastal dynamics, serving as a benchmark for climate adaptation measures in other cyclone-prone regions.

Precipitation forecasting: from geophysical aspects to machine learning applications

Intense precipitation events pose a significant threat to human life. Mathematical and computational models have been developed to simulate atmospheric dynamics to predict and understand these climates and weather events. However, recent advancements in artificial intelligence (AI) algorithms, particularly in machine learning (ML) techniques, coupled with increasing computer processing power and meteorological data availability, have enabled the development of more cost-effective and robust computational models that are capable of predicting precipitation types and aiding decision-making to mitigate damage. In this paper, we provide a comprehensive overview of the state-of-the-art in predicting precipitation events, addressing issues and foundations, physical origins of rainfall, potential use of AI as a predictive tool for forecasting, and computational challenges in this area of research. Through this review, we aim to contribute to a deeper understanding of precipitation formation and forecasting aided by ML algorithms.

Comparative changes in seasonal marine heatwaves and cold spells over the Tropical Indian Ocean during recent decades and disentangling the drivers of highly intense events

AbstractThe unprecedented increase in the Sea Surface Temperature (SST) in the warming climate yield stress to the system and pose severe threats to the marine ecosystem. Marine Heatwaves (MHWs) and Marine Cold Spells (MCSs) are two extreme events related to SST variability. For better management of ocean productivity, marine ecosystem, marine services, and fisheries, the understanding of seasonal discrepancies rather than annual documentation of MHWs and MCSs metrics is more utilitarian. This study documents the decadal changes in the MHWs and MCSs over the Tropical Indian Ocean (TIO) for all seasons. Additionally, highly intense events (based on intensity and duration) are identified and demonstrate the associated drivers. During the past two decades (1982–1990, 1991–2000), the MCSs were more frequent than MHWs in every season. However, in the recent two decades (2001–2010, 2011–2020), TIO become more prone to MHWs with considerably more frequent and prolonged events in JJAS months. Moreover, MCSs are disappearing from the TIO. It was noted that the choice of baseline period has an impact on the magnitude of MHWs and MCSs changes, but the spatial pattern (regions with high/low magnitude MHWs and MCSs) stays fairly constant in all baseline period sensitivity checks. The investigation of highly intense events reveals that MHWs and MCSs are produced and sustained by the same drivers when they are at their opposing edges. In general, the coherence effort from winds, net heat fluxes (shortwave radiation, longwave radiation, latent heat flux, and sensible heat flux), mixed level depth, and mean sea level pressure contribute to the genesis of seasonal MHWs or MCSs events. Additionally, in some cases, a single driver (e.g., wind) may also play a crucial role in these extreme events. The remote climate modes of variability, such as El Niño–Southern Oscillation, also contribute significantly to the MHWs and MCSs. El Niño (La Niña) events not only increase the spatial coverage of MHWs (MCSs) but also increases the intensity.

Spatiotemporal rainfall variability and its relationship to flash flood risk in Northeastern Sylhet Haor of Bangladesh

Abstract The variability and distribution of rainfall are uniquely significant for climatic risk prediction. This study aims to assess spatiotemporal rainfall variability and flash flood intensity events in the Sylhet haor region of Bangladesh by analyzing rainfall data from April for the period 1995–2022. For this, we used both Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) data and Bangladesh Meteorological Department (BMD) daily rainfall data. Rainfall patterns were studied using zonal statistics in ArcGIS and graphical illustration. The results revealed that the rainfall pattern was erratic and showed a range of spatiotemporal variability. If the average rainfall exceeds 250 mm in Meghalaya and Assam and 400 mm in Sylhet, severe flash floods may occur in the Sylhet haor region. An increase in pre-monsoon rainfall and its shift from May to April may increase the intensity of flash floods and consequently damage the rice crop. This finding might help flood management agencies to develop flood management strategies, prepare flood contingency plans, provide real-time and advanced warnings to strengthen flood warning and forecasting systems, and schedule seasonal agricultural activities.

Composition and distribution of the zooplankton community along the west coast of Baja California peninsula and its relationships with the environment variables

The year 2014 is between one of the coldest La Niña events (2011−2012), and one of the most intense warming events between (2013–2016) in the California Current System (CCS). The information provided in this work documents part of the missing information about zooplankton and oceanographic features for the year 2014 along the southern portion of the CCS off the western Coast of Baja California Peninsula (WBCP). The statistical analysis of environmental variables during the summer of 2014 distinguished three regions off the WBCP (north, transitional, and south), in coincidence with changes in zooplankton groups composition. Thermal and saline oceanic fronts off the central region coincided with an increasing abundance of gelatinous zooplankton, where two cold core eddies were present. These mesoscale structures represent physical barriers that seem to determine the distribution limits of planktonic communities. Since no day/night statistical differences in zooplankton composition were found, zooplankton community changes seem more related to the latitudinal environmental changes and mesoscale semi-permanent structures in the middle peninsula.

Analysis of redox-sensitive trace elements to the reconstruction of the depositional paleoenvironment of the Ponta Grossa Formation in southern Brazil

In the Devonian period, several intense climatic changes occurred on Earth, such as global cooling and intense volcanic eruption events, increasing the amount of organic matter in water bodies and forming a bituminous sedimentary material containing redox-sensitive trace elements, called shale. Among the places with this type of rock formation from the Devonian period, one of them is the Ponta Grossa region, located in the Paraná Basin, southern Brazil, which lacks studies that use metals to understand the depositional environment of its formation. Therefore, this study aims to analyze the redox-sensitive trace elements together with the total organic carbon to understand the depositional environment at the time of the formation of these shales. For this, outcrop samples were collected and analyzed regarding the total organic carbon and the redox-sensitive trace elements, generating ratios between them. From the results obtained, it was observed that the environment was warmer and humid, with very low salinity, a greater tendency to anoxia, periods of greater primary productivity, and marine transgressions. Thus, it was possible to know the depositional environment of organic matter that later originated the shale deposits in this region of the planet.

Progradational‐to‐retrogradational styles of Palaeogene fluvial fan successions in the San Juan Basin, New Mexico

AbstractBasin‐scale outcrop analyses of fluvial architecture in the Palaeogene San Juan Basin, New Mexico, document lateral and vertical trends in channel, floodplain and palaeosol characteristics. Herein, the uppermost part of the Palaeocene Nacimiento Formation and lower Eocene Cuba Mesa and Regina Members of the San Jose Formation are identified as deposits of large fluvial fans based on trends observed across the basin. Stratigraphic trends suggest two packages originated by fluvial fan progradation. Progradation of the lower fan system provides a new explanation for the transitional nature of a disconformity at the Nacimiento–San Jose Formation contact, previously thought to be a low‐angle unconformity. The two fan systems are separated by a retrogradational interval that culminates in a depositional hiatus at the contact between the Cuba Mesa and Regina Members. This, combined with poor age constraints, indicates that the duration of the disconformity at the base of the Cuba Mesa Member may have been overestimated. Furthermore, the succession is interpreted as deposits of variable‐discharge rivers, based on the combined abundance of upper flow regime and high deposition rate sedimentary structures indicative of intense flooding events, preservation of in‐channel bioturbation and paedogenic modification indicating periods of prolonged dryness, lack of identifiable bar strata and alternations of poorly drained and well‐drained floodplain deposits with pedofacies indicating alternating wet–dry cycles. This dataset adds to a growing body of evidence linking the formation of large fluvial fans to discharge variability and thus to hydroclimates with significant inter‐ and intra‐annual precipitation variability and intense rainfall. A long‐term stratigraphic shift from poorly drained to well‐drained floodplain deposits across two progradational fan successions indicates that a predictive model suggesting downstream decreases in soil drainage conditions is not encompassing of all large fan systems, and instead suggests a transition to a more arid climate across the Palaeocene–Eocene boundary.