New biochronological scales of planktic foraminifera for the early danian based on high-resolution biostratigraphy

After the Cretaceous/Paleogene boundary (KPB) catastrophic mass extinction event, an explosive evolutionary radiation of planktic foraminifera took place in consequence of the prompt occupation of empty niches. The rapid evolution of new species makes it possible to establish high-resolution biozonations in the lower Danian. We propose two biostratigraphic scales for low-to-middle latitudes spanning the first two million years of the Danian. The first is based on qualitative data and includes four biozones: the Guembelitria cretacea Zone (Dan1), the Parvularugoglobigerina longiapertura Zone (Dan2), the Parvularugoglobigerina eugubina Zone (Dan3), and the Parasubbotina pseudobulloides Zone (Dan4). The latter two are divided into several sub-biozones: the Parvularu-goglobigerina sabina Subzone (Dan3a) and the Eoglobigerina simplicissima Subzone (Dan3b) for the Pv. eugubina Zone, and the Praemurica taurica Subzone (Dan4a), the Subbotina triloculinoides Subzone (Dan4b), and the Globanomalina compressa Subzone (Dan4c) for the P. pseudobulloides Zone. The second scale is based on quantitative data and includes three acme-zones (abundance zones): the Guembelitria Acme-zone (DanAZ1), the Parvularugoglobigerina-Palaeoglobigerina Acme-zone (DanAZ2), and the Woodringina-Chiloguembelina Acme-zone (DanAZ3). Both biozonations are based on high-resolution samplings of the most continuous sections of the lower Danian worldwide and have been calibrated with recent magnetochronological and astrochronological dating

Revalidation of the genus Chiloguembelitria Hofker: Implications for the evolution of early Danian planktonic foraminifera

Guembelitria is the only planktonic foraminiferal genus whose survival from the mass extinction event of the Cretaceous/Paleogene (K/Pg) boundary has been clearly proven. The evolution of Guembelitria after the K/Pg boundary led to the appearance of two guembelitriid lineages in the early Danian: one biserial, represented by Woodringina and culminating in Chiloguembelina, and the other trochospiral, represented by Trochoguembelitria and culminating in Globoconusa. We have re-examined the genus Chiloguembelitria, another guembelitriid descended from Guembelitria and whose taxonomic validity had been questioned, it being considered a junior synonym of the latter. Nevertheless, Chiloguembelitria differs from Guembelitria mainly in the wall texture (pustulate to rugose vs. pore-mounded) and the position of the aperture (umbilical-extraumbilical to extraumbilical vs. umbilical). Chiloguembelitria shares its wall texture with Trochoguembelitria and some of the earliest specimens of Woodringina, suggesting that it played an important role in the evolution of early Danian guembelitriids, as it seems to be the most immediate ancestor of both trochospiral and biserial lineages. Morphological and morphostatistical analyses of Chiloguembelitria discriminate at least five species: Chg. danica, Chg. irregularis, and three new species: Chg. hofkeri, Chg. trilobata and Chg. biseriata

An updated suprageneric classification of planktic foraminifera after growing evidence of multiple benthic-planktic transitions

Planktic foraminifera have traditionally been classified within a single order: Globigerinida. However, recent phylogenetic studies, both molecular and stratophenetic, are evidencing the polyphyletic origin of planktic foraminifera from several benthic ancestors. At least four independent events of benthic-planktic transition have been identified. One of them occurred after the Cretaceous–Paleogene boundary mass extinction, originating the first Cenozoic globigerinids. Another three occurred in the Mesozoic, originating three groups of planktic foraminifera (globotruncanids, heterohelicids and guembelitriids) not related phylogenetically to each other or to current globigerinids. These findings make it necessary to carry out an exhaustive review of their suprageneric systematics, mainly at the order level. Here we propose a new, more natural classification, grouping them into four orders: Globigerinida, Heterohelicida, Globotruncanida n. ord., and Guembelitriida n. ord. To better reflect the diversity and phylogeny of planktic foraminifera, we have also defined two new superfamilies: Abathomphaloidea n. superfam. and Parvularugoglobigerinoidea n. superfam., and one new family: Parvularuglobigerinidae n. fam

Microwave-assisted CO2 reforming of coke oven gas: An exception to the general rule?

It has been previously reported that the dry reforming of methane can be enhanced by means of microwave heating. In this article, this technology is applied to the CO2 reforming of coke oven gas (COG). The results obtained were opposite to those reported in the CO2 reforming of CH4, since in the case of the COG, microwave heating only slightly enhanced the conversions when an activated carbon was used as catalyst, whereas the results achieved when mixtures of activated carbon and Ni/Al 2O3 were employed as catalyst were even worse than those obtained in a conventional oven. Several hypotheses were considered in order to find an explanation for these poor results, the nature of the microplasmas formed during the process being the most likely factor. The high proportions of H2 present in the reactor when the dry reforming of coke oven gas is carried out may give rise to microplasmas of higher temperature than in the dry reforming of CH4. This will cause the Ni particles to sinter significantly, leading to a decrease in the conversions

Microwave-assisted CO2 reforming of coke oven gas: An exception to the general rule?

It has been previously reported that the dry reforming of methane can be enhanced by means of microwave heating. In this article, this technology is applied to the CO2 reforming of coke oven gas (COG). The results obtained were opposite to those reported in the CO2 reforming of CH4, since in the case of the COG, microwave heating only slightly enhanced the conversions when an activated carbon was used as catalyst, whereas the results achieved when mixtures of activated carbon and Ni/Al 2O3 were employed as catalyst were even worse than those obtained in a conventional oven. Several hypotheses were considered in order to find an explanation for these poor results, the nature of the microplasmas formed during the process being the most likely factor. The high proportions of H2 present in the reactor when the dry reforming of coke oven gas is carried out may give rise to microplasmas of higher temperature than in the dry reforming of CH4. This will cause the Ni particles to sinter significantly, leading to a decrease in the conversions

Microwave-assisted CO2 reforming of coke oven gas: An exception to the general rule?

It has been previously reported that the dry reforming of methane can be enhanced by means of microwave heating. In this article, this technology is applied to the CO2 reforming of coke oven gas (COG). The results obtained were opposite to those reported in the CO2 reforming of CH4, since in the case of the COG, microwave heating only slightly enhanced the conversions when an activated carbon was used as catalyst, whereas the results achieved when mixtures of activated carbon and Ni/Al 2O3 were employed as catalyst were even worse than those obtained in a conventional oven. Several hypotheses were considered in order to find an explanation for these poor results, the nature of the microplasmas formed during the process being the most likely factor. The high proportionsof H2 present in the reactor when the dry reforming of coke oven gas is carried out may give rise to microplasmas of higher temperature than in the dry reforming of CH4. This will cause the Ni particles to sinter significantly, leading to a decrease in the conversions

Smooth and rugose wall textures in earliest Danian trochospiral planktic foraminifera from Tunisia

New scanning electron microscopy (SEM) photographs of planktic foraminiferal specimens from Tunisian sections (El Kef, Aïn Settara, Elles) have revealed the occurrence of two lineages of primitive trochospiral species in the lowermost Danian. The first lineage to appear, which evolves at the P0-Pa transition, exhibits a smooth and/or granular wall texture (with pore-murals), and its species were attributed to the parvularugoglobigerinids (Parvularugoglobigerina and Palaeoglobigerina). The second to appear at the Pa-P1 transition has a rugose wall texture (with rugosities and isolated irregular pore-mounds) and is herein assigned to the new genus Trochoguembelitria. Both lineages co-occur in the upper part of Pa (middle-upper part of Eoglobigerina simplicissima Subzone), containing quasi-homeomorph species - pseudocryptic under stereomicroscopy - only differentiated under SEM by their wall texture (e.g., Palaeoglobigerina alticonusa vs Trochoguembelitria alabamensis). The data at our disposal suggest Trochoguembelitria derived from triserial Guembelitria and its species evolved in parallel with the parvularugoglobigerinids in the earliest Danian.Fil: Arenillas, Ignacio. Universidad de Zaragoza; EspañaFil: Arz, José A.. Universidad de Zaragoza; EspañaFil: Nañez, Carolina Adela. Secretaría de Industria y Minería. Servicio Geológico Minero Argentino; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Propiedades, ventajas e inconvenientes de los materiales utilizados en supercondensadores

Este trabajo recoge una visión general de las propiedades, ventajas e inconvenientes de los principales materiales usados en los electrodos de los condensadores electroquímicos (también denominados supercondensadores). La elección de estos materiales tiene una enorme influencia en las características finales del dispositivo electroquímico. Entre los materiales de electrodo disponibles para su aplicación en supercondensadores se incluyen los materiales porosos basados en carbón, los óxidos de metales de transición y los polímeros conductores. Cada una de estas familias de materiales presenta unas ventajas e inconvenientes, por ello, en numerosas ocasiones no se emplea un único tipo de material para la elaboración de los electrodos, sino que la tendencia va dirigida hacia el uso de electrodos híbridos, es decir, aquellos constituidos por materiales de distinta naturaleza que combinan los aspectos beneficiosos y compensan las limitaciones de cada uno de los materiales por separado

Contribution of orbital forcing and Deccan volcanism to global climatic and biotic changes across the Cretaceous-Paleogene boundary at Zumaia, Spain

Untangling the timing of the environmental effects of Deccan volcanism with respect to the Chicxulub impact is instrumental to fully assessing the contributions of both to climate change over the Cretaceous-Paleogene boundary (KPB) interval. Despite recent improvements in radiometric age calibrations, the accuracy of age constraints and correlations is insufficient to resolve the exact mechanisms leading to environmental and climate change in the 1 m.y. across the KPB. We present new high-resolution planktic foraminiferal, geochemical, and geophysical data from the Zumaia section (Spain), calibrated to an updated orbitally tuned age model. We provide a revised chronology for the major carbon isotope excursions (CIEs) and planktic foraminiferal events and test temporal relationships with different models of the eruptive phases of the Deccan Traps. Our data show that the major CIEs near the KPB, i.e., the late Maastrichtian warming event (66.25–66.10 Ma) and the Dan-C2 event (65.8–65.7 Ma), are synchronous with the last and the first 405 k.y. eccentricity maximum of the Maastrichtian and the Danian, respectively, and that the minor Lower C29n event (65.48–65.41 Ma) is well constrained to a short eccentricity maximum. Conversely, we obtained evidence of abrupt environmental change likely related to Deccan volcanism at ca. 65.9 Ma, based on a bloom of opportunistic triserial guembelitriids (Chiloguembelitria). The orbital, isotopic, and paleobiological temporal relationships with Deccan volcanism established here provide new insights into the role of Deccan volcanism in climate and environmental change in the 1 m.y. across the KPB. © 2021. The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license

Hypothesis testing on the planktic foraminiferal survival model after the KPB mass extinction: evidence from Tunisia and Algeria

A historical review of the extinction, survival, and evolutionary models of planktic foraminifera proposed for the Cretaceous/Paleogene boundary (KPB) mass extinction event sometimes leaves the impression that there is still no conclusive evidence to support any single one of them. Two main models have been put forward: i) catastrophic mass extinction, almost total for some authors, compatible with the geologically instantaneous paleoenvironmental effects of a large meteorite impact (Chicxulub impact, Mexico); and ii) gradual mass extinction, compatible with the paleoenvironmental effects of massive, long-lasting volcanism (Deccan Traps, India). Over the years, a lot of evidence has been proposed supporting one hypothesis or the other, highlighting isotopic (delta O-18, delta C-13, Sr-87/Sr-86) as well as taphonomic, biostratigraphic, quantitative (relative and/or absolute abundance), phylogenetic, and even teratological. We review previous planktic foraminiferal and stable isotope studies, and provide new quantitative and statistical tests from two pelagic sections: the El Kef section (Tunisia), recognized as the most continuous and expanded lowermost Danian section worldwide, and the Sidi Ziane section (Algeria), affected by relevant hiatus in the lower Danian. The results indicate that all the latest Maastrichtian planktic foraminiferal species except those of Guembelitria went extinct exactly at the KPB, supporting the hypothesis of an almost total extinction. In the light of this new evidence, we maintain that the Maastrichtian planktic foraminiferal specimens found worldwide in lower Danian samples could be the result of similar reworking and vertical mixing processes to those at El Kef and Sidi Ziane