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

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

Disentangling Eocene/Oligocene ocean changes in the NW Atlantic using planktic foraminifera, stable isotopes and other proxies

El tránsito Eoceno-Oligoceno (EOT en siglas inglesas) estuvo asociado a un enfriamiento pronunciado del océano y a cambios en la circulación oceánica que culminó con la formación inicial del casquete polar de la Antártida hace ~34 Ma. Un conjunto creciente de evidencias sedimentológicas, geoquímicas y micropaleontológicas en el Hemisferio Norte sugieren que la circulación oceánica del Atlántico Norte jugó un importante rol en los cambios climáticos ocurridos durante el EOT. Esta Tesis Doctoral contribuye con una revisión de los eventos oceanográficos y climáticos ocurridos entre hace 36 y 33 Ma basada en el análisis de las asociaciones micropaleontológicas (foraminíferos planctónicos, foraminíferos bentónicos y nanofósiles calcáreos) y de los isótopos estables (δ18O y δ13C) obtenidos de las conchas excepcionalmente bien preservadas de foraminíferos provenientes del margen Oeste del Atlántico Norte (DSDP Site 612). Este sondeo es de latitud media (paleolatitud 41°18’N, 48°54’W) y está situado en el talud continental de New Jersey (paleoprofundidad ~1000 m). En la actualidad, probablemente como en el EOT, se halla en la confluencia de la Corriente del Golfo, que fluye hacia el norte, y la Corriente del Labrador, que fluye hacia el sur, mientras que el fondo oceánico es bañado por el Agua Profunda del Atlántico Norte (NADW en siglas inglesas). Los datos isotópicos y bioestratigráficos indican que la primera fase del EOT (EOT-1 y el límite Eoceno/Oligoceno, o EOB en siglas inglesas) está registrada en los sedimentos del Sondeo 612. Sin embargo, el evento de glaciación Antártica Oi-1 está truncado por un hiato, sobre el cual se conserva únicamente una fina capa del Oligoceno.El estudio cuantitativo de las asociaciones micropaleontológicas y las mediciones isotópicas de oxígeno y carbono en conchas de foraminíferos planctónicos y bentónicos han permitido identificar cambios significativos en las condiciones de las aguas superficiales y profundas del Atlántico Norte durante los 2.87 Ma estudiados del Eoceno tardío y Oligoceno temprano. Este periodo puede dividirse en cuatro fases paleoambientales, las cuales pueden reflejar los cambios en el aporte de nutrientes y mezcla vertical acontecidos durante los 2.5 Ma anteriores al EOB en el Atlántico Norte. Estos cambios son consistentes con la intensificación de las aguas profundas provenientes del norte que venía ocurriendo desde hace 36 Ma y que provocó alteraciones en las corrientes superficiales. Los resultados de esta Tesis Doctoral son importantes para entender los eventos globales asociados con la rápida expansión de la criosfera en el Oligoceno temprano.The Eocene-Oligocene climate transition (EOT) was associated with pronounced global cooling and changes in ocean circulation that culminated in the onset of Antarctic glaciation ~34 Ma ago. A growing body of sedimentologic, geochemical and micropaleontologic evidence recognizes consistent changes in the Northern Hemisphere that imply an important role for North Atlantic Ocean circulation during the EOT. This PhD thesis contributes new insights about the oceanographic and climatic events occurred between 36 and 33 Ma based on micropaleontological assemblage analysis (planktic foraminifera, benthic foraminifera and calcareous nannofossils) and stable isotope data (δ18O and δ13C) on exceptionally well preserved (glassy) foraminifera from DSDP Site 612 on the western North Atlantic margin. This midlatitude site (paleolatitude 41°18’N, 48°54’W) is located on the New Jersey Continental Slope (palaeodepth ~1000 m). In the present, as well as likely during EOT time, it sits at the confluence of today’s north flowing Gulf Stream and south flowing Labrador surface currents. Today Site 612 seafloor is bathed by North Atlantic Deep Water. Isotopic and biostratigraphic data indicate that the first phase of the EOT (EOT-1 and the Eocene/Oligocene boundary, EOB) is captured in Site 612 sediments but the rest, i.e. the Oi-1 Antarctic glaciation event, is truncated by a hiatus, with only a sliver of early Oligocene strata surviving. According to recognized micropaleontological assemblages and oxygen and carbon stable isotope measurements on benthic and planktic foraminifera, significant changes in surface and deep-water conditions have been identified in the 2.87 Myrs of the late Eocene and early Oligocene. This period can be divided into four paleoenvironmental phases, which can reflect the changes in nutrient supply and vertical mixing occurred during the 2.5 Myrs prior to the EOB in the North Atlantic. These changes are consistent with shifting influence of surface currents linked here to strengthening of northern-sourced deep water production, from 36 Ma. The results of this PhD thesis are important for piecing together the global events associated with the rapid expansion of the cryosphere in the early Oligocene.<br /

New species of the genus Trochoguembelitria from the lowermost Danian of Tunisia – biostratigraphic and evolutionary implications in planktonic foraminifera

Two lineages of primitive trochospiral species emerged in the earliest Danian after the Cretaceous/Paleogene (K/Pg) mass extinction event, one exhibiting a smooth wall texture with mural pores and the other, a pustulate to rugose wall texture consisting of blunt pustules and small rugosities, imperforate or with decentred pores, and scattered pore-mounds. This evolutionary scenario is based on Tunisian sections, particularly the El Kef section, whose continuity, completeness, abundance and excellent preservation of the foraminifera make it the best locality worldwide for analyzing the taxonomy and evolution of the early Danian planktonic foraminifera. The first lineage appeared about 5 kyr after the K/Pg boundary catastrophic mass extinction and is attributed to the parvularugoglobigerinids (Parvularugoglobigerina and Palaeoglobigerina). The second lineage appeared approximately 35 kyr after the K/Pg boundary event and is assigned to Trochoguembelitria Arenillas, Arz & Náñez, 2012. Morphological and morphostatistical analyses of Trochoguembelitria discriminate at least four species, two of them usually assigned to parvularugoglobigerinids: T. alabamensis (Liu & Olsson, 1992) and T. extensa (Blow, 1979); and two new species: T. liuae sp. nov. and T. olssoni sp. nov

El límite Cretácico/Paleógeno del corte de Agost revisado: reconstrucción paleoambiental y patrón de extinción en masa

El evento del límite Cretácico/Paleógeno (K/Pg) ha sido intensamente estudiado en el corte español de Agost, que contiene uno de los tránsitos Cretácico-Paleógeno más continuos y expandidos en el área del Tetis. Por este motivo, se considera como una sección clásica del límite K/Pg, y ha sido detalladamente analizada por numerosos especialistas desde el punto de vista micropaleontológico, paleoicnológico, magnetoestratigráfico, mineralógico y geoquímico. Los sedimentos del Cretácico Superior (Biozonas de Abathomphalus mayaroensis y de Plummerita hantkeninoides) y del Paleógeno inferior (Biozonas de Guembelitria cretacea, de Parvularugoglobigerina eugubina y de Parasubbotina pseudobulloides) corresponden a una secuencia principalmente margosa rica en microfósiles, depositada en la parte superior y media del talud, tal y como indican las asociaciones de foraminíferos bentónicos. En el Daniense basal se identifica una capa arcillosa oscura que contiene evidencias de impacto. Los foraminíferos planctónicos muestran un patrón de extinción en masa catastrófico en coincidencia con el límite K/Pg, situado en la base de esta capa arcillosa. El 70% de las especies se extinguieron claramente en coincidencia con en el límite K/Pg. Muy pocas especies parecen extinguirse en el Maastrichtiense final y podrían interpretarse como parte del patrón de extinción de fondo o el remanente efecto Signor-Lipps. Algunas especies cretácicas parecen sobrevivir el evento y desaparecer gradualmente en el Daniense, tal vez como resultado de los efectos a más largo plazo del impacto meteorítico. Sin embargo, su presencia en el Daniense también podría ser interpretada como resultado de la reelaboración. Teniendo en cuenta estas consideraciones, el porcentaje de especies de foraminíferos planctónicos que se extinguieron en el evento del límite K/Pg alcanzaría el 90%. A pesar de que los foraminíferos bentónicos, al contrario que los foraminíferos planctónicos, no sufrieron una extinción en masa, la drástica reorganización de sus asociaciones en coincidencia con el límite refleja importantes cambios paleoambientales, compatibles con los efectos catastróficos causados por el impacto de un asteroide justo en el límite Cretácico/Paleógeno

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

Cicloestratigrafía y paleoclimatología del tránsito Selandiense-Thanetiense (Paleoceno) de Zumaia (Guipúzcoa) con foraminíferos planctónicos y susceptibilidad magnética.

Este Trabajo Fin de Grado (TFG) tiene como objetivo realizar interpretaciones paleoclimáticas de un intervalo deaproximadamente 200 ka (entre 59,3 Ma y 59,1 Ma) del transito Selandiense-Thanetiense (Paleoceno medio-superior) en el tramo de Zumaia (Gipuzkoa). Zumaia contiene un excepcional registro cicloestratigráfico, con ciclos de precesión bien reflejados por una alternancia de margas y calizas. Se han estudiado un total de 20 muestras, 10 correspondiente al Selandiense y los otros 10 al Thanetiense, lo que representa 10 ciclos de precesión. <br /